Urine

Duration

Research looking at the duration of urination in a range of mammal species found that nine larger species urinated for 21 ± 13 seconds irrespective of body size.^[5] Smaller species, including rodents and bats, cannot produce steady streams of urine and instead urinate with a series of drops.^[5]

Quantity

Tigers spray small quantities of urine to mark their territories.^[6]

The adult human bladder typically holds between 300 and 500 ml (10 and 17 fl oz) of urine before urination, but it can hold considerably more.^[7][8] Average urine production in adult humans is around 1.4 L (0.31 imp gal; 0.37 US gal) of urine per person per day with a normal range of 0.6 to 2.6 L (0.13 to 0.57 imp gal; 0.16 to 0.69 US gal) per person per day, produced in around 6 to 8 urinations per day depending on state of hydration, activity level, environmental factors, weight, and the individual's health.^[9] Producing too much or too little urine needs medical attention. Polyuria is a condition of excessive production of urine (> 2.5 L/day), oliguria when < 400 mL are produced, and anuria being < 100 mL per day.

Constituents

About 91–96% of urine consists of water.^[9] The remainder can be broadly characterized into inorganic salts, urea, organic compounds, and organic ammonium salts.^[9][10] Urine also contains proteins, hormones, and a wide range of metabolites,^[11] varying by what is introduced into the body.^{[citation needed]}

The total solids in urine are on average 59 g (2.1 oz) per day per person.^[11] Urea is the largest constituent of the solids, constituting more than 50% of the total. The daily volume and composition of urine varies per person based on the amount of physical exertion, environmental conditions, as well as water, salt, and protein intakes.^[9] In healthy persons, urine contains very little protein and an excess is suggestive of illness, as with sugar.^[11] Organic matter, in healthy persons, also is reported to be at most 1.7 times more matter than minerals.^[10] However, any more than that is suggestive of illness.^[10]

Lesser amounts and concentrations of other compounds and ions are often present in urination of humans.^[11]

Color

Urine varies in appearance, depending principally upon a body's level of hydration, interactions with drugs, compounds and pigments or dyes found in food, or diseases.^[11] Normally, urine is a transparent solution ranging from colorless to amber, but is usually a pale yellow.^[11] Usually urination color comes primarily from the presence of urobilin.^[14] Urobilin is a final waste product resulting from the breakdown of heme from hemoglobin during the destruction of aging blood cells.^[15][16]

Colorless urine indicates over-hydration. Colorless urine in drug tests can suggest an attempt to avoid detection of illicit drugs in the bloodstream through over-hydration.

• Bloody urine is termed hematuria, a symptom of a wide variety of medical conditions.
• Reddish or brown urine may be caused by porphyria (not to be confused with the harmless,^[11] temporary pink or reddish tint caused by beeturia).
• Pinkish urine can result from the consumption of beets (beeturia)^[11]
• Dark yellow urine is often indicative of dehydration.
• Orange urine due to certain medications such as rifampin and phenazopyridine
• Dark orange to brown urine can be a symptom of jaundice, rhabdomyolysis, or Gilbert's syndrome.
• Greenish urine can result from the consumption of asparagus or foods,^{[citation needed]} beverages with green pigments, or from a urinary tract infection.^[11]
• Blue urine can be caused by the ingestion of methylene blue (e.g., in medications) or foods or beverages with blue dyes.
• Blue urine stains can be caused by blue diaper syndrome.
• Purple urine may be due to purple urine bag syndrome.
• Black or dark-colored urine is referred to as melanuria and may be caused by a melanoma or non-melanin acute intermittent porphyria.

• 
  Dark urine due to low fluid intake.
• 
  Dark red urine due to blood (hematuria).
• 
  Dark red urine due to choluria.
• 
  Pinkish urine due to consumption of beetroots.
• 
  Green urine during long term infusion of the sedative propofol.

Odor

Sometime after leaving the body, urine may acquire a strong ammonia-like odor due to bacterial decomposition of urea into ammonia.^[18] Fresh urine from healthy individuals typically has only a mild odor. Abnormally strong or unpleasant urine odor may occur in association with dehydration, diet, or urinary tract infections.^[19]

The odor of normal human urine can reflect what has been consumed or specific diseases.^[11] For example, an individual with diabetes mellitus may present a sweetened urine odor. This can be due to kidney diseases as well, such as kidney stones.^{[citation needed]} Additionally, the presence of amino acids in urine (diagnosed as maple syrup urine disease) can cause it to smell of maple syrup.^[20]

Eating asparagus can cause a strong odor reminiscent of the vegetable caused by the body's breakdown of asparagusic acid.^[21] Likewise consumption of saffron, alcohol, coffee, tuna fish, and onion can result in telltale scents.^[22] Particularly spicy foods can have a similar effect, as their compounds pass through the kidneys without being fully broken down before exiting the body.^[23][24]

pH

The pH normally is within the range of 5.5 to 7 with an average of 6.2.^[9] In persons with hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder.^[25] Urine pH can be monitored by a physician or at home.^[26]

A diet which is high in protein from meat and dairy, as well as alcohol consumption can reduce urine pH, whilst potassium and organic acids, such as from diets high in fruit and vegetables, can increase the pH and make it more alkaline.^[9]

Cranberries, popularly thought to decrease the pH of urine, have actually been shown not to acidify urine.^[27] Drugs that can decrease urine pH include ammonium chloride, chlorothiazide diuretics, and methenamine mandelate.^[28][29]

Density

Human urine has a specific gravity of 1.003–1.035.^[9]

Bacteria and pathogens

Urine is not sterile, not even in the bladder,^[30][31] contrary to longstanding popular belief. This opened a new area of study: the urinary microbiome. In the urethra, epithelial cells lining the urethra are colonized by facultatively anaerobic Gram-negative rod and cocci bacteria.^[32] One study conducted in Nigeria isolated a total of 77 distinct bacterial strains from 100 healthy children (ages 5–11) as well as 39 strains from 33 cow urine samples, a considerable amount being pathogens.^[33] Pathogens identified and their percentages were:

The study also states:

Multiple antibiotic resistance (MAR) rates recorded in children urinal bacterial species were 37.5–100% (Gram-positive) and 12.5–100% (Gram-negative), while MAR among the cow urinal bacteria was 12.5–75.0% (Gram-positive) and 25.0–100% (Gram-negative).

Source of medications

Urine contains proteins and other substances that are useful for medical therapy and are ingredients in many prescription drugs. Urine from postmenopausal women is rich in gonadotropins that can yield follicle stimulating hormone and luteinizing hormone for fertility therapy.^[38] One such commercial product is Pergonal.^[39]

Urine from pregnant women contains enough human chorionic gonadotropins for commercial extraction and purification to produce hCG medication. Pregnant mare urine is the source of estrogens, namely Premarin.^[38] Urine also contains antibodies, which can be used in diagnostic antibody tests for a range of pathogens, including HIV-1.^[40]

Urine can also be used to produce urokinase, which is used clinically as a thrombolytic agent.^[41][42]

Fertilizer

Cleaning

Given that urea in urine breaks down into ammonia, urine has been used for cleaning. In pre-industrial times, urine was used – in the form of lant or aged urine – as a cleaning fluid.^[56] Urine was also used for whitening teeth in Ancient Rome.^[57]

Gunpowder

Urine was used before the development of a chemical industry in the manufacture of gunpowder. Urine, a nitrogen source, was used to moisten straw or other organic material, which was kept moist and allowed to rot for several months to over a year. The resulting salts were washed from the heap with water, which was evaporated to allow collection of crude saltpeter crystals, that were usually refined before being used in making gunpowder.^[58]

Survival uses

Urophagia is the consumption of urine. Urine was consumed in several ancient cultures for various health, healing, and cosmetic purposes. People have been known to drink urine in extreme cases of water scarcity.

The US Army Field Manual advises against drinking urine for survival. The manual explains that drinking urine tends to worsen rather than relieve dehydration due to the salts in it, and that urine should not be consumed in a survival situation, even when there is no other fluid available. In hot weather survival situations, where other sources of water are not available, soaking cloth (a shirt for example) in urine and putting it on the head can help cool the body.^[59]

During World War I, Germans experimented with numerous poisonous gases as weapons. After the first German chlorine gas attacks, Allied troops were supplied with masks of cotton pads that had been soaked in urine. It was believed that the ammonia in the pad neutralized the chlorine. These pads were held over the face until the soldiers could escape from the poisonous fumes.^{[citation needed]}

Urban legend states that urine works well against jellyfish stings.^[60] This scenario has appeared many times in popular culture including in the Friends episode "The One With the Jellyfish", an early episode of Survivor, as well as the films The Real Cancun (2003), The Heartbreak Kid (2007) and The Paperboy (2012). However, at best it is ineffective, and in some cases this treatment may make the injury worse.^[61][62][63]

Textiles

Urine has often been used as a mordant to help prepare textiles, especially wool, for dyeing. In the Scottish Highlands and Hebrides, the process of "waulking" (fulling) woven wool is preceded by soaking in urine, preferably infantile.^[64]

Olfactory communication

Urine plays a role in olfactory communication, since it contains semiochemicals that act as pheromones.^[65][66] The urine of predator species often contains kairomones^[67] that serve as a repellent against their prey species.^[68]