If one drinks a liter of water at 7 am when (in what span) will that water be eliminated through uresis?
Is that process influenced by any factors such as empty stomach, sleep or other?
The time from drinking to urination depends mainly on your hydration status and the presence of food in the stomach.
Scenario: You have drunk enough fluid in the previous days, so you are normally hydrated. In the morning, you get up from the bed, urinate, drink 1 liter of water in 5 minutes and eat nothing.
Some water can come through the stomach and can be absorbed in the small intestine in about 5 minutes; the entire liter may need more than 2 hours (sweatscience.com).
When some water is absorbed into the blood it can immediately trigger diuresis - the excretion of the urine through the kidneys into the bladder. It may take about 3 hours for the entire amount of water drunk to be excreted. So, the approximate time span (from start to end of water excretion) could be 5 - 180 minutes. But not likely the entire liter of water will be excreted, because, in the morning, you are in a slightly negative water balance, so some water will stay in your body.
If you are dehydrated before starting drinking, much less urine will be excreted in the first few hours.
If you drink after eating, the food in the stomach can delay water absorption and excretion by more than an hour. This also happens when you drink nutritional fluids, such as milk or juice.
This is from my experience and understanding basic physiology. I'll try to find some references.
It is a hypothetical question which is not a true scenario I would try to explain the process of water absorption and excetrtion.
when a person consumes water it is absorbed into blood stream (liquid as well as in the form of water in food consumed). The amount of water absorbed in the stomach and how quickly water is absorbed depends, in part, on how much has been eaten. If someone is drinking water on an empty stomach, they are more likely to experience a faster rate of water absorption - as quick as 5 minutes after taking a drink. Whereas, if a person has eaten a lot of food before they drink water, the speed of absorption will slow down accordingly and absorption could take up to a few hours.
Approximately only 20% directly makes to the bladder remaining water would be utilized for performing vital function of the body.
Once the human body uses up all the water it needs to function efficiently, it begins the process of removing excess water.The water is not only excreted solely through uresis (urine is only 95% water), the other routes for water excretion is sweat, fecal route and saliva.Small droplets of water also exit the body via the breath.
As water is not excreted thought sole route is not possible to calculate the exact time taken for removal from the body.
Water intoxication, also known as water poisoning, hyperhydration, overhydration, or water toxemia, is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake.
Under normal circumstances, accidentally consuming too much water is exceptionally rare. Nearly all deaths related to water intoxication in normal individuals have resulted either from water-drinking contests, in which individuals attempt to consume large amounts of water, or from long bouts of exercise during which excessive amounts of fluid were consumed.  In addition, water cure, a method of torture in which the victim is forced to consume excessive amounts of water, can cause water intoxication.
Water, just like any other substance, can be considered a poison when over-consumed in a brief period of time. Water intoxication mostly occurs when water is being consumed in a high quantity without adequate electrolyte intake. 
Excess of body water may also be a result of a medical condition or improper treatment see "hyponatremia" for some examples. Water is considered one of the least toxic chemical compounds, with an LD50 of over 150 ml/kg in rats. 
Marathon Runners: Beware Of Drinking Too Much Water
Many runners know it&rsquos important to drink plenty of water during a marathon to keep their bodies hydrated. However, drinking too much water during the course of a 26-mile race can actually kill them.
&ldquoThis condition, hyponatremia, occurs when you have low sodium in your body,&rdquo said Dr. James Muntz, internal medicine service chief with The Methodist Hospital in Houston. &ldquoWhen sodium levels drop in the fluids outside the cells, water will get in there and attempt to balance the concentration of salt outside the cells.&rdquo
The abundance of water will cause the cells to swell. Most cells can adapt to change, however, the brain cannot. When this occurs in less than 48 hours, it can be fatal if not treated immediately.
Symptoms of hyponatremia include:
- Loss of appetite.
- Abnormal mental status (hallucinations, confusion, change in personality, etc.)
- Muscle weakness.
A few days before the race you can take steps to try and prevent hyponatremia by using sports drinks during training and increasing your salt intake, as long as you don&rsquot have high blood pressure.
&ldquoDuring the marathon a good rule of thumb is to drink about one cup of fluid every 20 minutes,&rdquo Muntz said. &ldquoDrinking any more than that over the course of the race can get you into trouble.&rdquo
A recent study of runners in the 2002 Boston Marathon found that 13 percent of those who finished the race developed hyponatremia. The majority of these runners reported feeling &ldquofine&rdquo after the race. However, if someone who feels &ldquofine&rdquo continues to drink water because they believe the nausea and weakness they are feeling is due to dehydration, they could easily end up having a seizure and falling into a coma.
&ldquoYou don&rsquot want to drink too much during the race, but if you do, sports drinks like Gatorade that contain salt, would be better than a lot of water,&rdquo Muntz said. &ldquoIf you experience any symptoms, see a physician immediately.&rdquo
Materials provided by Methodist Hospital, Houston. Note: Content may be edited for style and length.
The biological half-life of water in a human is about 7 to 14 days. It can be altered by behavior. Drinking large amounts of alcohol will reduce the biological half-life of water in the body.   This has been used to decontaminate humans who are internally contaminated with tritiated water (tritium). The basis of this decontamination method (used at Harwell) [ citation needed ] is to increase the rate at which the water in the body is replaced with new water.
The removal of ethanol (drinking alcohol) through oxidation by alcohol dehydrogenase in the liver from the human body is limited. Hence the removal of a large concentration of alcohol from blood may follow zero-order kinetics. Also the rate-limiting steps for one substance may be in common with other substances. For instance, the blood alcohol concentration can be used to modify the biochemistry of methanol and ethylene glycol. In this way the oxidation of methanol to the toxic formaldehyde and formic acid in the human body can be prevented by giving an appropriate amount of ethanol to a person who has ingested methanol. Note that methanol is very toxic and causes blindness and death. A person who has ingested ethylene glycol can be treated in the same way. Half life is also relative to the subjective metabolic rate of the individual in question.
Common prescription medications Edit
|Adenosine||Less than 10 seconds (estimate) |
|Norepinephrine||2 minutes |
|Oxaliplatin||14 minutes |
|Zaleplon||1 hour |
|Morphine||1.5–4.5 hours |
|Flurazepam||2.3 hours |
in rare cases up to 8 days 
Active metabolite (nordazepam): 30–200 hours 
Active lipophilic metabolite (norfluoxetine): 4–16 days 
The biological half-life of caesium in humans is between one and four months. This can be shortened by feeding the person prussian blue. The prussian blue in the digestive system acts as a solid ion exchanger which absorbs the caesium while releasing potassium ions.
For some substances, it is important to think of the human or animal body as being made up of several parts, each with their own affinity for the substance, and each part with a different biological half-life (physiologically-based pharmacokinetic modelling). Attempts to remove a substance from the whole organism may have the effect of increasing the burden present in one part of the organism. For instance, if a person who is contaminated with lead is given EDTA in a chelation therapy, then while the rate at which lead is lost from the body will be increased, the lead within the body tends to relocate into the brain where it can do the most harm. 
- in the body has a biological half-life of about 30 to 50 days. in the body has a biological half-life of about one to four months. (as methylmercury) in the body has a half-life of about 65 days.
- Lead in the blood has a half life of 28–36 days.  in bone has a biological half-life of about ten years. in bone has a biological half-life of about 30 years. in bone has a biological half-life of about 100 years. in the liver has a biological half-life of about 40 years.
Peripheral half-life Edit
Some substances may have different half-lives in different parts of the body. For example, oxytocin has a half-life of typically about three minutes in the blood when given intravenously. Peripherally administered (e.g. intravenous) peptides like oxytocin cross the blood-brain-barrier very poorly, although very small amounts (< 1%) do appear to enter the central nervous system in humans when given via this route.  In contrast to peripheral administration, when administered intranasally via a nasal spray, oxytocin reliably crosses the blood–brain barrier and exhibits psychoactive effects in humans.   In addition, also unlike the case of peripheral administration, intranasal oxytocin has a central duration of at least 2.25 hours and as long as 4 hours.   In likely relation to this fact, endogenous oxytocin concentrations in the brain have been found to be as much as 1000-fold higher than peripheral levels. 
First-order elimination Edit
|Time (t)||Percent of initial value||Percent completion|
|t½ × 2||25%||75%|
|t½ × 3||12.5%||87.5%|
|t½ × 3.322||10.00%||90.00%|
|t½ × 4||6.25%||93.75%|
|t½ × 4.322||5.00%||95.00%|
|t½ × 5||3.125%||96.875%|
|t½ × 6||1.5625%||98.4375%|
|t½ × 7||0.781%||99.219%|
|t½ × 10||0.098%||99.902%|
where k is the reaction rate constant. Such a decay rate arises from a first-order reaction where the rate of elimination is proportional to the amount of the substance: 
The half-life for this process is 
Alternatively, half-life is given by
where λz is the slope of the terminal phase of the time–concentration curve for the substance on a semilogarithmic scale.  
Half-life is determined by clearance (CL) and volume of distribution (VD) and the relationship is described by the following equation:
In clinical practice, this means that it takes 4 to 5 times the half-life for a drug's serum concentration to reach steady state after regular dosing is started, stopped, or the dose changed. So, for example, digoxin has a half-life (or t½) of 24–36 h this means that a change in the dose will take the best part of a week to take full effect. For this reason, drugs with a long half-life (e.g., amiodarone, elimination t½ of about 58 days) are usually started with a loading dose to achieve their desired clinical effect more quickly.
Biphasic half-life Edit
Many drugs follow a biphasic elimination curve — first a steep slope then a shallow slope:
STEEP (initial) part of curve —> initial distribution of the drug in the body. SHALLOW part of curve —> ultimate excretion of drug, which is dependent on the release of the drug from tissue compartments into the blood.
The longer half-life is called the terminal half-life and the half-life of the largest component is called the dominant half-life.  For a more detailed description see Pharmacokinetics § Multi-compartmental models.
Calculate when you are sober again after drinking alcohol
Do NOT use this calculation as an absolute source to whether you can drive or operate a motorized vehicle! If you have consumed alcohol, the only safe method is to leave the car the day after. If you really want to see whether you are sober enough to drive or not, you should purchase an breathalyzer (like this cheap one or this quality breathalyzer) (for next time). It will give you the exact alcohol level of your blood. It is better that YOU check it than the police, right!?
This calculation uses alcohol given in volume percent. It is half the alcohol proof. I.e. 100 alcohol proof = 50% and 40 alcohol proof = 20 %.
What is broken?
Is there something wrong with the calculation Calculate when you are sober again after drinking alcohol? Is it a bug or has it gone completely offline? Please, let us know what is wrong! If the calculation did not give you the result you expected, please write which values you used and what you expected the calculation to do.
What happens if you drink too much water?
Every cell in the body needs water to function correctly. However, drinking too much can lead to water intoxication and serious health consequences.
It is difficult to drink too much water by accident, but it can happen, usually as a result of overhydrating during sporting events or intense training.
The symptoms of water intoxication are general — they can include confusion, disorientation, nausea, and vomiting.
In rare cases, water intoxication can cause swelling in the brain and become fatal.
This article describes the symptoms, causes, and effects of water intoxication. It also looks into how much water a person should drink each day.
Share on Pinterest A person may experience water intoxication if they drink too much water.
Also known as water poisoning, water intoxication is a disruption of brain function caused by drinking too much water.
Doing so increases the amount of water in the blood. This can dilute the electrolytes, especially sodium, in the blood.
If sodium levels fall below 135 millimoles per liter (mmol/l), doctors refer to the issue as hyponatremia.
Sodium helps maintain the balance of fluids inside and outside of cells. When sodium levels drop due to excessive water consumption, fluids travel from the outside to the inside of cells, causing them to swell.
When this happens to brain cells, it can be dangerous and even life threatening.
Bottom line: Water intoxication results from drinking too much water. The excess water dilutes sodium in the blood and causes fluids to move inside cells, causing them to swell.
When a person consumes an excessive amount of water and cells in their brain start to swell, the pressure inside their skull increases. This causes the first symptoms of water intoxication, which include:
Severe cases of water intoxication can produce more serious symptoms, such as:
- drowsiness or cramping
- increased blood pressure
- inability to identify sensory information
A buildup of fluid in the brain is called cerebral edema. This can affect the brain stem and cause central nervous system dysfunction.
In severe cases, water intoxication can cause seizures, brain damage, a coma, and even death.
Bottom line: Drinking too much water can increase the pressure inside the skull. This can cause various symptoms and, in severe cases, become fatal.
Water intoxication is rare, and it is very difficult to consume too much water by accident. However, it can happen — there have been numerous medical reports of death due to excessive water intake.
Water intoxication most commonly affects people participating in sporting events or endurance training, or people who have various mental health conditions.
Water intoxication is particularly common among endurance athletes. It can happen if a person drinks a lot of water without correctly accounting for electrolyte losses.
For this reason, hyponatremia often occurs during major sporting events.
As the authors of one study report, out of 488 participants in the 2002 Boston Marathon, 13% had hyponatremia symptoms, and 0.06% had critical hyponatremia, with sodium levels of less than 120 mmol/l.
Instances of water intoxication at these events have resulted in death. One case involved a runner who had collapsed after a marathon.
Because he was improperly rehydrated, his sodium levels fell below 130 mmol/l. The runner then developed water on the brain, known as hydrocephalus, and a hernia in his brain stem, which caused his death.
One medical report described 17 soldiers who developed hyponatremia after drinking too much water during training. Their blood sodium levels were 115–130 mmol/l, while the normal range is 135–145 mmol/l.
According to another report , three soldiers died due to hyponatremia and cerebral edema. These deaths were associated with drinking more than 5 liters of water in just a few hours.
The symptoms of hyponatremia can be misinterpreted as those of dehydration. According to one report , a soldier who received an incorrect diagnosis of dehydration and heat stroke died from water intoxication as a result of rehydration efforts.
Mental health conditions
Compulsive water drinking, also called psychogenic polydipsia , can be a symptom of various mental health conditions.
It is most common among people with schizophrenia, but it can also arise in people with affective disorders, psychosis, and personality disorders.
Bottom line: Water intoxication can be life threatening, and it is most common among soldiers in training, endurance athletes, and people with schizophrenia.
It is difficult to consume too much water by accident. However, it can happen, and there have been numerous reports of death due to excess water intake.
People at risk of death from water intoxication tend to be participating in endurance sporting events or military training. A person who is doing neither is unlikely to die from drinking too much water.
Overhydration and water intoxication happen when a person drinks more water than their kidneys can get rid of via urine.
The amount of water is not the only factor — time also plays a role.
According to figures quoted in a 2013 study, the kidneys can eliminate about 20–28 liters of water a day, but they can remove no more than 0.8 to 1.0 liters every hour.
To avoid hyponatremia, it is important not to outpace the kidneys by drinking more water than they can eliminate.
The authors of the study report that hyponatremia symptoms can develop if a person drinks 3–4 liters of water in a short period, though they do not give a specific time estimate.
According to one case report , soldiers developed symptoms after consuming at least 2 quarts (1.9 liters) of water per hour.
Another report describes the development of hyponatremia after drinking more than 5 liters in a few hours.
Water intoxication and prolonged hyponatremia also occurred in an otherwise healthy 22-year-old prisoner who drank 6 liters of water in 3 hours.
Finally, according to one report , a 9-year-old girl developed water intoxication after consuming 3.6 liters of water in 1–2 hours.
Bottom line: The kidneys can remove 20–28 liters of water per day, but they cannot excrete more than 0.8 to 1.0 liters per hour. Drinking more than this can be harmful.
According to the Centers for Disease Control and Prevention (CDC) , there are no official guidelines about how much water a person needs to drink each day.
The right amount differs, depending on factors such as body weight, level of physical activity, the climate, and whether they are breastfeeding.
In 2004, The National Academy of Medicine recommended that women aged 19–30 consume around 2.7 liters per day and men of the same age around 3.7 liters per day.
Some people still follow the 8×8 rule, which recommends drinking eight 8-ounce glasses of water per day. However, this was not based on research.
Relying on thirst may not work for everyone. Athletes, older adults, and pregnant women, for example, may need to drink more water each day.
To estimate the right amount, it can help to consider calories. If a person needs 2,000 calories per day, they should also consume 2,000 milliliters of water per day.
Drinking too much water can lead to water intoxication. This is rare and tends to develop among endurance athletes and soldiers.
There are no official guidelines about how much water to drink. To avoid water intoxication, some sources recommend drinking no more than 0.8 to 1.0 liters of water per hour.
How is Alcohol Eliminated from the Body?
Once ethanol is in the circulation, it reaches all tissues in the body, including the brain, where it causes intoxication. Our bodies are designed to terminate the action of drugs, including alcohol, so that the intoxication doesn’t persist when a person stops drinking. In fact, the body starts eliminating ethanol before it even gets into the general circulation!
Ethanol moves from the GI tract to the liver
When a person consumes alcohol, the first place that the alcohol goes after it leaves the GI tract is the liver (Figure 1.10). Once it enters the capillaries surrounding the stomach and small intestines, the capillaries lead to the portal vein, which enters the liver and branches out once again into capillaries. Ethanol diffuses from the capillaries (with the concentration gradient) into the nearby hepatic cells (the major cells of the liver). In the hepatic (liver) cells, some of the ethanol is converted, or detoxified by enzymes to inactive products. This process is called metabolism, and the products are called metabolites.
Figure 1.10 Alcohol moves from the GI tract through the portal vein to the liver. It diffuses into hepatic cells of the liver where it is metabolized.
Alcohol is metabolized in 2 stages
Metabolism of drugs by liver enzymes serves two purposes. First, metabolism is a way of “turning off” the action of a drug. In general, metabolites have less biological activity relative to the parent compound, although there are some exceptions to this rule, as we will see with ethanol.
Second, metabolism helps to convert the drug into a more polar (water-soluble) form so it can be carried in the bloodstream to the kidneys, where it is excreted in the urine (water-based). During metabolism, the enzymes actually help speed up the reactions however, the speed is different for different people.
Stage 1: Ethanol to acetaldehyde
Although some alcohol is metabolized in the stomach, the primary site of metabolism is in the liver. The cytoplasm of liver cells contain an enzyme called alcohol dehydrogenase (ADH) that catalyzes the oxidation of ethanol to acetaldehyde (Figure 1.11). The oxidation occurs when ethanol binds to a site on the ADH enzyme and loses some electrons in the form of H atoms. Actually ethanol gives up 2 H atoms to another molecule that also binds to ADH. In this case, the recipient molecule of the electrons is called a coenzyme. Without the coenzyme, the ADH enzyme won’t work.
The primary metabolite of ethanol oxidation, is acetaldehyde. This compound is relatively toxic, and it is responsible for alcohol-related flushing, headaches, nausea, and increased heart rate. These toxic effects of acetaldehyde contribute to the alcohol “hang-over” that persists for a significant time after drinking.
Figure 1.11 Ethanol is oxidized by ADH to acetaldehyde in the cytoplasm, and then the acetaldehyde is oxidized by ALDH in the mitochondria to acetic acid.
Stage 2: Acetaldehyde to acetic acid
The body has a natural way to “get rid” of the acetaldehyde—a second liver enzyme, present in the mitochondria, is acetaldehyde dehydrogenase (ALDH). This enzyme metabolizes acetaldehyde to acetic acid (Figure 1. 11), which is inactive. The acetic acid is eventually converted in the cell into carbon dioxide and water. Some people do not have the ability to metabolize acetaldehyde very well. When they drink alcohol, acetaldehyde accumulates in the blood and makes them feel sick. They have facial flushing, headaches, nausea, vomiting, and a rapid heart rate. The reason that some people can’t metabolize acetaldehyde very well is because they have a form of ALDH that has a mutation in the gene that codes for it. The alternative form of ALDH is very inefficient at metabolizing acetaldehyde. People with this genetic mutation do not like to drink alcohol.To learn more about different forms of ALDH and ADH in various populations, see Module 2I.
Overwhelming the alcohol metabolizing enzymes
There is enough ADH present in a person’s liver to metabolize all the alcohol molecules from one drink quite efficiently within an hour or two. The rate of metabolism remains constant during continued drinking. Why is this important? As the consumption of alcohol increases there just aren’t enough ADH molecules (in the liver or the stomach) to metabolize the extra alcohol efficiently. So, alcohol begins to accumulate in the bloodstream, giving an increased blood alcohol concentration (BAC) (Figure 1.12) that leads to intoxication. In other words, when the metabolism of ethanol is limited by the number of ADH enzyme molecules present, it proceeds independent of the amount of alcohol in the bloodstream.
Figure 1.12 The number of ADH enzyme molecules in the liver is limited. With more than one drink of alcohol, the enzymes become saturated with ethanol molecules. Some ethanol is metabolized in the liver, but the rest of the ethanol leaves the liver and accumulates in the bloodstream.
Alcohol that is not metabolized on its first passage through the liver continues to circulate throughout the body as an active drug. Ultimately, only a small fraction of the ingested alcohol escapes metabolism. This small amount of alcohol (5-10%) is eliminated unchanged in the breath as vapor or in the urine.
The small intestine, also known as the small bowel, is where digestive juices from your liver and pancreas mix with food to break it down into usable nutrients. It is also responsible for absorbing these nutrients from the food you eat. Over 20 feet in length, the small intestine also delivers the leftovers that aren't absorbed -- the waste -- to your colon, upward of 1 liter per day. Given a standard diet and a healthy gut, it can take 2.5 to 3 hours to empty half of your small intestine, or it can take longer than 10 hours.
The large bowel, including the cecum, colon and rectum, is more muscular than the small intestine and is between 5 and 6 feet long. The primary job of the colon is to absorb any remaining nutrients and to push undigested food and waste through to your rectum to be expelled. It also absorbs water, changing the waste product from a liquid mush to a firmer stool that's easier to pass. It takes 7 to 16 hours to absorb all of the necessary fluid. Overall, it can take between 30 and 40 hours for food to fully pass through your colon, assuming a healthy diet and no constipation.
Zinc in Your Diet
You can meet your body's need for zinc by eating meats, beans, fish, fortified cereals and nuts. Oysters are also a rich source of zinc. The recommended daily allowance (RDA) of zinc for a male who's 19 years of age and over is 11 mg, and a female of the same age would need 8 mg, according to the NIH Office of Dietary Supplements. Your body has no mechanism for storing zinc, so whatever isn't used is expelled from the body, and you'll need a steady dietary supply to keep your body functioning well.
Anatomy of the bladder and outlet
The main organs involved in urination are the urinary bladder and the urethra. The smooth muscle of the bladder, known as the detrusor, is innervated by sympathetic nervous system fibers from the lumbar spinal cord and parasympathetic fibers from the sacral spinal cord.  Fibers in the pelvic nerves constitute the main afferent limb of the voiding reflex the parasympathetic fibers to the bladder that constitute the excitatory efferent limb also travel in these nerves. Part of the urethra is surrounded by the male or female external urethral sphincter, which is innervated by the somatic pudendal nerve originating in the cord, in an area termed Onuf's nucleus. 
Smooth muscle bundles pass on either side of the urethra, and these fibers are sometimes called the internal urethral sphincter, although they do not encircle the urethra. Further along the urethra is a sphincter of skeletal muscle, the sphincter of the membranous urethra (external urethral sphincter). The bladder's epithelium is termed transitional epithelium which contains a superficial layer of dome-like cells and multiple layers of stratified cuboidal cells underneath when evacuated. When the bladder is fully distended the superficial cells become squamous (flat) and the stratification of the cuboidal cells is reduced in order to provide lateral stretching.
The physiology of micturition and the physiologic basis of its disorders are subjects about which there is much confusion, especially at the supraspinal level. Micturition is fundamentally a spinobulbospinal reflex facilitated and inhibited by higher brain centers such as the pontine micturition center and, like defecation, subject to voluntary facilitation and inhibition. 
In healthy individuals, the lower urinary tract has two discrete phases of activity: the storage (or guarding) phase, when urine is stored in the bladder and the voiding phase, when urine is released through the urethra. The state of the reflex system is dependent on both a conscious signal from the brain and the firing rate of sensory fibers from the bladder and urethra.  At low bladder volumes, afferent firing is low, resulting in excitation of the outlet (the sphincter and urethra), and relaxation of the bladder.  At high bladder volumes, afferent firing increases, causing a conscious sensation of urinary urge. When the individual is ready to urinate, he or she consciously initiates voiding, causing the bladder to contract and the outlet to relax. Voiding continues until the bladder empties completely, at which point the bladder relaxes and the outlet contracts to re-initiate storage.  The muscles controlling micturition are controlled by the autonomic and somatic nervous systems. During the storage phase, the internal urethral sphincter remains tense and the detrusor muscle relaxed by sympathetic stimulation. During micturition, parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax. The external urethral sphincter (sphincter urethrae) is under somatic control and is consciously relaxed during micturition.
In infants, voiding occurs involuntarily (as a reflex). The ability to voluntarily inhibit micturition develops by the age of 2–3 years, as control at higher levels of the central nervous system develops. In the adult, the volume of urine in the bladder that normally initiates a reflex contraction is about 300–400 millilitres (11–14 imp fl oz 10–14 US fl oz).
During storage, bladder pressure stays low, because of the bladder's highly compliant nature. A plot of bladder (intravesical) pressure against the depressant of fluid in the bladder (called a cystometrogram), will show a very slight rise as the bladder is filled. This phenomenon is a manifestation of the law of Laplace, which states that the pressure in a spherical viscus is equal to twice the wall tension divided by the radius. In the case of the bladder, the tension increases as the organ fills, but so does the radius. Therefore, the pressure increase is slight until the organ is relatively full. The bladder's smooth muscle has some inherent contractile activity however, when its nerve supply is intact, stretch receptors in the bladder wall initiate a reflex contraction that has a lower threshold than the inherent contractile response of the muscle.
Action potentials carried by sensory neurons from stretch receptors in the urinary bladder wall travel to the sacral segments of the spinal cord through the pelvic nerves.  Since bladder wall stretch is low during the storage phase, these afferent neurons fire at low frequencies. Low-frequency afferent signals cause relaxation of the bladder by inhibiting sacral parasympathetic preganglionic neurons and exciting lumbar sympathetic preganglionic neurons. Conversely, afferent input causes contraction of the sphincter through excitation of Onuf's nucleus, and contraction of the bladder neck and urethra through excitation of the sympathetic preganglionic neurons.
Diuresis (production of urine by the kidney) occurs constantly, and as the bladder becomes full, afferent firing increases, yet the micturition reflex can be voluntarily inhibited until it is appropriate to begin voiding.
Voiding begins when a voluntary signal is sent from the brain to begin urination, and continues until the bladder is empty.
Bladder afferent signals ascend the spinal cord to the periaqueductal gray, where they project both to the pontine micturition center and to the cerebrum.  At a certain level of afferent activity, the conscious urge to void becomes difficult to ignore. Once the voluntary signal to begin voiding has been issued, neurons in pontine micturition center fire maximally, causing excitation of sacral preganglionic neurons. The firing of these neurons causes the wall of the bladder to contract as a result, a sudden, sharp rise in intravesical pressure occurs. The pontine micturition center also causes inhibition of Onuf's nucleus, resulting in relaxation of the external urinary sphincter.  When the external urinary sphincter is relaxed urine is released from the urinary bladder when the pressure there is great enough to force urine to flow out of the urethra. The micturition reflex normally produces a series of contractions of the urinary bladder.
The flow of urine through the urethra has an overall excitatory role in micturition, which helps sustain voiding until the bladder is empty. 
Many men, and some women, may sometimes briefly shiver after or during urination. 
After urination, the female urethra empties partially by gravity, with assistance from muscles. [ clarification needed ] Urine remaining in the male urethra is expelled by several contractions of the bulbospongiosus muscle, and, by some men, manual squeezing along the length of the penis to expel the rest of the urine.
For land mammals over 1 kilogram, the duration of urination does not vary with body mass, being dispersed around an average of 21 seconds (standard deviation 13 seconds), despite a 4 order of magnitude (1000×) difference in bladder volume.   This is due to increased urethra length of large animals, which amplifies gravitational force (hence flow rate), and increased urethra width, which increases flow rate. For smaller mammals a different phenomenon occurs, where urine is discharged as droplets, and urination in smaller mammals, such as mice and rats, can occur in less than a second.  The posited benefits of faster voiding are decreased risk of predation (while voiding) and decreased risk of urinary tract infection.
The mechanism by which voluntary urination is initiated remains unsettled.  One possibility is that the voluntary relaxation of the muscles of the pelvic floor causes a sufficient downward tug on the detrusor muscle to initiate its contraction.  Another possibility is the excitation or disinhibition of neurons in the pontine micturition center, which causes concurrent contraction of the bladder and relaxation of the sphincter. 
There is an inhibitory area for micturition in the midbrain. After transection of the brain stem just above the pons, the threshold is lowered and less bladder filling is required to trigger it, whereas after transection at the top of the midbrain, the threshold for the reflex is essentially normal. There is another facilitatory area in the posterior hypothalamus. In humans with lesions in the superior frontal gyrus, the desire to urinate is reduced and there is also difficulty in stopping micturition once it has commenced. However, stimulation experiments in animals indicate that other cortical areas also affect the process.
The bladder can be made to contract by voluntary facilitation of the spinal voiding reflex when it contains only a few milliliters of urine. Voluntary contraction of the abdominal muscles aids the expulsion of urine by increasing the pressure applied to the urinary bladder wall, but voiding can be initiated without straining even when the bladder is nearly empty.
Voiding can also be consciously interrupted once it has begun, through a contraction of the perineal muscles. The external sphincter can be contracted voluntarily, which will prevent urine from passing down the urethra.
Experience of urination
The need to urinate is experienced as an uncomfortable, full feeling. It is highly correlated with the fullness of the bladder.  In many males the feeling of the need to urinate can be sensed at the base of the penis as well as the bladder, even though the neural activity associated with a full bladder comes from the bladder itself, and can be felt there as well. In females the need to urinate is felt in the lower abdomen region when the bladder is full. When the bladder becomes too full, the sphincter muscles will involuntarily relax, allowing urine to pass from the bladder. Release of urine is experienced as a lessening of the discomfort.
Many clinical conditions can cause disturbances to normal urination, including:
- , the inability to hold urine
- Mixed incontinence, a combination of the two types of incontinence
- Piss off! (to express contempt see above)
- Pissing down (to refer to heavy rain) (an unproductive ego-driven battle)
- Pisshead (vulgar way to refer to someone who drinks too much alcohol)
- Piss ant (a worthless person in non-slang usage the term refers to several species of ant whose colonies have a urine-like odor)
- Pissing up a flagpole (to partake in a futile activity)
- Pissing into the wind (to act in ways that cause self-harm)
- Piss away (to squander or use wastefully) (to take liberties, be unreasonable, or to mock another person)
- Full of piss and vinegar (energetic or ambitious late adolescent or young adult male)
- Piss up (British expression for drinking to get drunk)
- Pissed (drunk in British English or angry in American English)
- , incontinence as a result of external mechanical disturbances , incontinence that occurs as a result of the uncontrollable urge to urinate
A drug that increases urination is called a diuretic, whereas antidiuretics decrease the production of urine by the kidneys.
Experimentally induced disorders
There are three major types of bladder dysfunction due to neural lesions: (1) the type due to interruption of the afferent nerves from the bladder (2) the type due to interruption of both afferent and efferent nerves and (3) the type due to interruption of facilitatory and inhibitory pathways descending from the brain. In all three types the bladder contracts, but the contractions are generally not sufficient to empty the viscus completely, and residual urine is left in the bladder. Paruresis, also known as shy bladder syndrome, is an example of a bladder interruption from the brain that often causes total interruption until the person has left a public area. These people (males) may have difficulty urinating in the presence of others and will consequently avoid using urinals without dividers or those directly adjacent to another person. Alternatively, they may opt for the privacy of a stall or simply avoid public toilets altogether.
When the sacral dorsal roots are cut in experimental animals or interrupted by diseases of the dorsal roots such as tabes dorsalis in humans, all reflex contractions of the bladder are abolished. The bladder becomes distended, thin-walled, and hypotonic, but there are some contractions because of the intrinsic response of the smooth muscle to stretch.
When the afferent and efferent nerves are both destroyed, as they may be by tumors of the cauda equina or filum terminale, the bladder is flaccid and distended for a while. Gradually, however, the muscle of the "decentralized bladder" becomes active, with many contraction waves that expel dribbles of urine out of the urethra. The bladder becomes shrunken and the bladder wall hypertrophied. The reason for the difference between the small, hypertrophic bladder seen in this condition and the distended, hypotonic bladder seen when only the afferent nerves are interrupted is not known. The hyperactive state in the former condition suggests the development of denervation hypersensitization even though the neurons interrupted are preganglionic rather than postganglionic.
Spinal cord injury
During spinal shock, the bladder is flaccid and unresponsive. It becomes overfilled, and urine dribbles through the sphincters (overflow incontinence). After spinal shock has passed, a spinally mediated voiding reflex ensues, although there is no voluntary control and no inhibition or facilitation from higher centers. Some paraplegic patients train themselves to initiate voiding by pinching or stroking their thighs, provoking a mild mass reflex. In some instances, the voiding reflex becomes hyperactive. Bladder capacity is reduced and the wall becomes hypertrophied. This type of bladder is sometimes called the spastic neurogenic bladder. The reflex hyperactivity is made worse, and may be caused, by infection in the bladder wall.
Due to the positions where the urethra exits the body, males and females often use different techniques for urination.
Most males prefer to urinate standing while others prefer to urinate sitting or squatting. Elderly males with prostate gland enlargement may benefit from sitting down while in healthy males, no difference is found in the ability to urinate.   For practising Muslim men, the genital modesty of squatting is also associated with proper cleanliness requirements or awrah. 
In human females, the urethra opens straight into the vulva. Hence, urination can take place while sitting or squatting for defecation. It is also possible for females to urinate while standing, and while clothed.  It is common for women in various regions of Africa to use this method when they urinate,    [ need quotation to verify ]    as do women in Laos.  [ failed verification ] Herodotus described a similar custom in ancient Egypt.  An alternative method for women to urinate standing is to use a tool known as a female urination device to assist. 
A common technique used in many developing nations involves holding the child by the backs of the thighs, above the ground, facing outward, in order to urinate. [ citation needed ]
The fetus urinates hourly and produces most of the amniotic fluid in the second and third trimester of pregnancy. The amniotic fluid is then recycled by fetal swallowing. 
Urination after injury
Occasionally, if a male's penis is damaged or removed, or a female's genitals/urinary tract is damaged, other urination techniques must be used. Most often in such cases, doctors will reposition the urethra to a location where urination can still be accomplished, usually in a position that would promote urination only while seated/squatting, though a permanent urinary catheter may be used in rare cases. [ citation needed ]
Alternative urination tools
Sometimes urination is done in a container such as a bottle, urinal, bedpan, or chamber pot (also known as a gazunder). A container or wearable urine collection device may be used so that the urine can be examined for medical reasons or for a drug test, for a bedridden patient, when no toilet is available, or there is no other possibility to dispose of the urine immediately.
An alternative solution (for traveling, stakeouts, etc.) is a special disposable bag containing absorbent material that solidifies the urine within seconds, making it convenient and safe to store and dispose of later. [ citation needed ]
It is possible for both genders to urinate into bottles in case of emergencies. The technique can help children to urinate discreetly inside cars and in other places without being seen by others. 
Babies have little socialized control over urination within traditions or families that do not practice elimination communication and instead use diapers. Toilet training is the process of learning to restrict urination to socially approved times and situations. Consequently, young children sometimes suffer from nocturnal enuresis. 
It is socially more accepted and more environmentally hygienic for those who are able, to urinate in a toilet. Public toilets may have urinals, usually for males, although female urinals exist, designed to be used in various ways. 
Urination without facilities
Acceptability of outdoor urination in a public place other than at a public urinal varies with the situation and with customs. Potential disadvantages include a dislike of the smell of urine, and some exposure of genitals. [ citation needed ] The latter can be unpleasant for the one who exposes them (modesty, lack of privacy) and/or those who can see them [ citation needed ] it can be avoided or mitigated by going to a quiet place and/or facing a tree or wall if urinating standing up, or while squatting, hiding the back behind walls, bushes, or a tree. [ citation needed ]
Portable toilets (port-a-potties) are frequently placed in outdoor situations where no immediate facility is available. These need to be serviced (cleaned out) on a regular basis. Urination in a heavily wooded area is generally harmless, actually saves water, and may be condoned for males (and less commonly, females) in certain situations as long as common sense is used. Examples (depending on circumstances) include activities such as camping, hiking, delivery driving, cross country running, rural fishing, amateur baseball, golf, etc.
The more developed and crowded a place is, the more public urination tends to be objectionable. In the countryside, it is more acceptable than in a street in a town, where it may be a common transgression. Often this is done after the consumption of alcoholic beverages, which causes production of additional urine as well as a reduction of inhibitions. One proposed way to inhibit public urination due to drunkenness is the Urilift, which is disguised as a normal manhole by day but raises out of the ground at night to provide a public restroom for bar-goers.
In many places, public urination is punishable by fines, though attitudes vary widely by country. In general, females are less likely to urinate in public than males. Women and girls, unlike men and boys, are restricted in where they can urinate conveniently and discreetly. 
The 5th-century BC historian Herodotus, writing on the culture of the ancient Persians and highlighting the differences with those of the Greeks, noted that to urinate in the presence of others was prohibited among Persians.  
There was [ when? ] a popular belief in the UK, that it was legal for a man to urinate in public so long as it occurred on the rear wheel of his vehicle and he had his right hand on the vehicle, but this is not true.  Public urination still remains more accepted by males in the UK, although British cultural tradition itself seems to find such practices objectionable. 
In Islamic toilet etiquette, it is haram to urinate while facing the Qibla, or to turn one's back to it when urinating or relieving bowels but modesty requirements for females make it impossible for girls to relieve themselves without facilities.   When toilets are unavailable, females can relieve themselves in Laos, Russia and Mongolia in emergency  but it remains less accepted for females in India even when circumstances make this a highly desirable option. 
Women generally need to urinate more frequently than men due to having smaller bladders.  Resisting the urge to urinate because of lack of facilities can promote urinary tract infections which can lead to more serious infections and, in rare situations, can cause renal damage in women.   Female urination devices are available to help women to urinate discreetly, as well to help them urinate while standing.
Standing versus sitting or squatting
In Western culture, the standing position is regarded by some as more comfortable and more masculine than the sitting or squatting option. [ citation needed ] However, in public restrooms without urinals and sometimes at home, men may be urged to use the sitting position as to diminish spattering of urine.  A systematic review meta-analysis of the effect of voiding position on the quality of urination found that in elderly males with benign prostate hyperplasia, the sitting position was superior compared with the standing.   Healthy males were not influenced by voiding position.
A literature review found cultural differences in socially accepted voiding positions around the world and found differences in preferred position: in the Middle-East and Asia, the squatting position was more prevalent, while in the Western world the standing and sitting positions were more common. 
Females usually sit or squat for urination, depending on what type of toilet they use: A squat toilet is used for urination in a squatting position. If there is no toilet available then a squatting or a half squat position is common. A partial squatting position (or "hovering") is taken up during urination by some women to avoid sitting on a potentially contaminated toilet seat or when using a female urinal. However, this may leave urine behind in the bladder.  It can also result in urine landing on the toilet seat.
Talking about urination
In many societies and in many social classes, even mentioning the need to urinate is seen as a social transgression, despite it being a universal need. Even today, many adults avoid stating that they need to urinate.  
Many expressions exist, some euphemistic and some vulgar. For example, centuries ago the standard English word (both noun and verb, for the product and the activity) was "piss", but subsequently "pee", formerly associated with children, has become more common in general public speech. Since elimination of bodily wastes is, of necessity, a subject talked about with toddlers during toilet training, other expressions considered suitable for use by and with children exist, and some continue to be used by adults, e.g. "weeing", "doing/having a wee-wee", "to tinkle", "go potty". [ citation needed ]
Other expressions include "squirting" and "taking a leak", and, predominantly by younger persons for outdoor female urination, "popping a squat", referring to the position many women adopt in such circumstances. National varieties of English show creativity. American English uses "to whiz".  Australian English has coined "I am off to take a Chinese singing lesson", derived from the tinkling sound of urination against the China porcelain of a toilet bowl.  British English uses "going to see my aunt", "going to see a man about a dog", "to piddle", "to splash (one's) boots", as well as "to have a slash", which originates from the Scottish term for a large splash of liquid.  One of the most common, albeit old-fashioned, euphemisms in British English is "to spend a penny", a reference to coin-operated pay toilets, which used (pre-decimalisation) to charge that sum. 
Use in language
References to urination are commonly used in slang. Usage in English includes:
- (to anger someone alternatively, to leave somewhere in a hurry)
Urination and sexual activity
Urolagnia, a paraphilia, is an inclination to obtain sexual enjoyment by looking at or thinking of urine or urination.  Urine may be consumed, or the person may bathe in it. Drinking urine is known as urophagia, though uraphagia refers to the consumption of urine regardless of whether the context is sexual. Involuntary urination during sexual intercourse is common, but rarely acknowledged. In one survey, 24% of women reported involuntary urination during sexual intercourse in 66% of sufferers urination occurred on penetration, while in 33% urine leakage was restricted to orgasm. 
Female kob may exhibit urolagnia during sex one female will urinate while the other sticks her nose in the stream.  
A male Patagonian mara, a type of rodent, will stand on his hind legs and urinate on a female's rump, to which the female may respond by spraying a jet of urine backwards into the face of the male.  The male's urination is meant to repel other males from his partner while the female's urination is a rejection of any approaching male when she is not receptive.  Both anal digging and urination are more frequent during the breeding season and are more commonly done by males. 
A male porcupine urinates on a female porcupine prior to mating, spraying the urine at high velocity.     
|Wikimedia Commons has media related to Urinating animals .|
While the primary purpose of urination is the same across the animal kingdom, urination often serves a social purpose beyond the expulsion of waste material.   In dogs and other animals, urination can mark territory or express submissiveness.  In small rodents such as rats and mice, it marks familiar paths.
The urine of animals of differing physiology or sex sometimes has different characteristics. For example, the urine of birds and reptiles is whitish, consisting of a pastelike suspension of uric acid crystals, and discharged with the feces of the animal via the cloaca, whereas mammals' urine is a yellowish colour, with mostly urea instead of uric acid, and is discharged via the urethra, separately from the feces. Some animals' (example: carnivores') urine possesses a strong odour, especially when it is used to mark territory or communicate in other ways. [ clarify ]
Stallions sometimes exhibit the Flehmen response by smelling the urine of a mare in heat.  A stallion sometimes scent marks his urination spots to make his position as herd stallion clear.  A male horse's penis is protected by a sheath when it is not in use for urination. 
Ring-tailed lemurs have also been shown to mark using urine. Behaviorally, there is a difference between regular urination, where the tail is slightly raised and a stream of urine is produced, and marking behavior, where the tail is held up in display and only a few drops are used.   The urine-marking behavior is typically used by females to mark territory, and has been observed primarily at the edges of the troop's territory and in areas where other troops may frequent.  The urine marking behavior is also most frequent during the mating season, and may play a role in reproductive communication between groups.  Many loris species also use urine for scent-marking.   The white-headed capuchin sometimes engages in a practice known as "urine washing", in which the monkey rubs urine on its feet.  Urine washing, in which urine is rubbed on the hands and feet, is also used by the Panamanian night monkey.  In some cases, strepsirrhines may also anoint themselves with urine. 
Hyenas do not raise their legs as canids do when urinating, as urination serves no territorial function for them. Instead, hyenas mark their territories using their anal glands, a trait found also in viverrids and mustelids, but not canids and felids.  Unlike other female mammals, female spotted hyenas urinate, copulate, and give birth through an organ called the pseudo-penis.  
Dog-like mammals (Canidae)
All canids (with the possible exception of dholes  ) use urine (combined with preputial gland secretions) to mark their territories. Many species of canids, including hoary foxes,  cape foxes,  and golden jackals,  use a raised-leg posture when urinating.   The scent of their urine is usually strongest in the winter, before the mating season. 
Domestic dogs mark their territories by urinating on vertical surfaces (usually at nose level), sometimes marking over the urine of other dogs.  When one dog marks over another dog's urine, this is known as "counter-marking" or "overmarking".   Male dogs urine-mark more frequently than female dogs,  typically beginning after the onset of sexual maturity.  Male dogs, as well as wolves, sometimes lift a leg and attempt to urinate even when their bladders are empty – this is known as a "raised-leg display",     "shadow-urination",  or "pseudo-urination".  They typically mark their territory due to the presence of new stimuli or social triggers in a dog's environment, as well as out of anxiety.  Marking behavior is present in both male and female dogs, and is especially pronounced in male dogs that have not been neutered. 
Raised-leg urination is the most significant form of scent marking in wolves, and is most frequent around the breeding season.  Wolves urine-mark more frequently when they detect the scent of other wolves, or other canid species.  Leg-lifting is more common in male wolves than female wolves, although dominant females also use the raised-leg posture.  Other types of urine-marking in wolves are FLU (flexed-leg urination), STU (standing urination), and SQU (squatting urination).  Breeding pairs of wolves will sometimes urinate on the same spot: this is known as "double-marking".       Double-marking is practiced by both coyotes and wolves.,    and also by foxes. 
Coyotes mark their territories by urinating on bushes, trees, or rocks.  Male coyotes usually lift their legs when scent-marking.  However, females sometimes also raise their legs, and males sometimes squat.  Urine marking is also associated with pair bonding in coyotes [ clarification needed ]  Coyotes sometimes urinate on their food, possibly to claim ownership over it. 
Red foxes use their urine to mark their territories.      A male fox raises one hind leg and his urine is sprayed forward in front of him, whereas a female fox squats down so that the urine is sprayed in the ground between the hind legs.   Urine is also used to mark empty cache sites, as reminders not to waste time investigating them.    Red foxes use various postures [ clarify ] to urinate, depending on where they are leaving a scent mark.  
As in most other canids, male bush dogs lift their hind legs when urinating. However, female bush dogs use a kind of handstand posture, which is less common in other canids.   When male bush dogs urinate, they create a spray instead of a stream. 
Both male and female maned wolves use their urine to communicate, e.g. mark their hunting paths or places where they have buried hunted prey.  The urine has a very distinctive smell, which some people liken to hops or cannabis. The responsible substance is very likely a pyrazine, which occurs in both plants.  (At the Rotterdam Zoo, this smell once set the police on a hunt for cannabis smokers.   )
Within the Felidae, male felids can urinate backwards by curving the tip of the glans penis backward.   Urine marking by felids is also known as "spray-urinating"  or "spray-marking".  To identify their territories, male tigers mark trees by spraying urine   and anal gland secretions, as well as marking trails with scat. Males show a grimacing face, called the Flehmen response, when identifying a female's reproductive condition by sniffing their urine markings.
Lions use urine to mark their territories. They often scrape the ground while urinating, and the urine often flows in short spurts, instead of flowing continuously. They often urinate on vegetation, or on tree trunks at least one meter high.  Male lions spray 1–20 jets of urine at an angle of 20–30 degrees upward, at a range of up to 4 meters behind them. 
Male cheetahs mark their territory by urinating on objects that stand out, such as trees, logs, or termite mounds. The whole coalition contributes to the scent. Males will attempt to kill any intruders, and fights result in serious injury or death.  When male cheetahs urine-mark their territories, they stand a meter away from a tree or rock surface with the tail raised, pointing the penis either horizontally backward or 60° upward.  The odor of cheetah urine (unlike that of other large felids) cannot be easily detected by humans. 
Black-footed cats use scent marking throughout their ranges, with males spraying urine up to 12 times an hour. 
By the time you feel thirsty, you are already on your way to dehydration, cautions the Centers for Disease Control and Prevention. It is especially important to consume sufficient fluids while you are in the sun, on hot days and while engaged in strenuous physical activity. If you urinate less frequently than usual and your skin is dry, you may need to drink more water. Additionally, your body may also retain extra fluid in response to hormones, heat or high salt intake. In these cases, consuming extra water may ease your symptoms. However, consult with your health care provider if you notice any unexplained swelling in your body.