Urine is the liquid by-product of metabolism.
Urine flows from the kidneys through the ureters to the urinary bladder, and is excreted from the body through the urethra by urination.
Cellular metabolism generates many by-products that are rich in nitrogen, such as urea, uric acid, and creatinine.
They must be cleared from the bloodstream.
Urination is the primary method for excreting water-soluble chemicals from the body.
A urinalysis can detect nitrogenous wastes of the body.
Urine plays an important role in the earth’s nitrogen cycle, and can be used as a fertilizer.
Some animals use it to mark their territories.
Human urine and feces, referred to as human waste or human excreta, and are managed via sanitation systems.
Soluble wastes are excreted primarily by the urinary system and, to a lesser extent in terms of urea, removed by perspiration.
The urinary tract system produces urine by a process of filtration, reabsorption, and tubular secretion.
The kidneys extract the soluble wastes from the bloodstream, as well as excess water, sugars, and a variety of other compounds.
Urine contains high concentrations of urea and other substances, including toxins.
Urine flows from the kidneys through the ureter, bladder, and finally the urethra before passing from the body.
Duration of urination is in a range of 21 ± 13 seconds.
Average urine production in adult humans is around 1.4 L of urine per person per day with a normal range of 0.6 to 2.6 L 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.
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.
About 91-96% of urine consists of water.
The remainder of urine is inorganic salts, urea, organic compounds, and organic ammonium salts, proteins, hormones, and a wide range of metabolites,varying by what is introduced into the body.
The total solids in urine are on average 59 g per day.
Urea is the largest constituent of the solids, constituting more than 50% of the total.
Urinary volume and composition varies based on the amount of physical exertion, environmental conditions, as well as water, salt, and protein intakes.
Urine contains very little protein and an excess is suggestive of illness, as with sugar.
Organic matter in urine is reported to at most 1.7 times more matter than minerals.
Values for the concentrations of constituents in fresh urine,
pH 6.2
Total nitrogen 8830 mg/L
Ammonium/ammonia-N 460 mg/L
Nitrate and nitrite 0.06 mg/L
Chemical oxygen demand 6000 mg/L
Total phosphorus 800 – 2000 mg/L
Potassium 2740 mg/L
Sulphate 1500 mg/L
Sodium 3450 mg/L
Magnesium 120 mg/L
Chloride 4970 mg/L
Calcium 230 mg/L
Urine color is a hydration status biomarker and, under normal conditions, correlates with urine specific gravity and urine osmolality.
The urine appearance depends principally on the level of hydration, interactions with drugs, compounds and pigments or dyes found in food, or with diseases.
Urine is a transparent solution ranging from colorless to amber.
It is usually a pale yellow.
Urine color comes primarily from the presence of urobilin.
Urobilin results from the breakdown of heme from hemoglobin during the destruction of aging blood cells.
Colorless urobilinogen is oxidized to yellow urobilin.
Colorless urine indicates over-hydration.
Dark yellow urine is often indicative of dehydration.
Yellowing may be caused by removal of excess riboflavin from the bloodstream.
Certain medications such as rifampin and phenazopyridine can cause orange urine.
Bloody urine is termed hematuria, a symptom of a wide variety of medical conditions.
Dark orange to brown urine can be a symptom of jaundice, rhabdomyolysis, or Gilbert’s syndrome.
Black or dark-colored urine; melanuria and may be caused by a melanoma or non-melanin acute intermittent porphyria.
Pinkish urine can result from the consumption of beets.
Greenish urine can result from the consumption of asparagus or foods,beverages with green pigments, or from a urinary tract infection.
Reddish or brown urine may be caused by porphyria.
Blue urine can be caused by the ingestion of methylene blue, 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.
Urine may acquire a strong “fish-like” odor because of contamination with bacteria: break down of urea by bacteria into ammonia.
Such an odor is not present in fresh urine of healthy individuals.
Urine odor reflect what has been consumed or may be associated with specific diseases: diabetics may present a sweetened urine odor, and can be due to kidney diseases as well, such as kidney stones.
The presence of amino acids in urine in maple syrup disease can cause it to smell of maple syrup.
Eating asparagus causes a strong odor as the the body breaks down asparagusic acid.
The consumption of saffron, alcohol, coffee, tuna fish, and onion and spicy foods can result in urine scents.
Urinary pH normally is within the range of 5.5 to 7 with an average of 6.2.
With hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder.
Consumptions of a high protein diet from meat and dairy, as well as alcohol consumption can reduce urine pH.
A diet high in potassium and organic acids, such as from diets high in fruit and vegetables, can increase the pH and make it more alkaline.
Cranberries, are thought to decrease the pH of urine, have actually been shown not to acidify urine.
Drugs that can decrease urine pH include ammonium chloride, chlorothiazide diuretics, and methenamine mandelate.
Human urine has a specific gravity of 1.003–1.035.
Urine is not sterile.
The urethral epithelial cells lining the urethra are colonized by facultatively anaerobic Gram-negative rod and cocci bacteria.
Pathogens identified and their percentages were:
Bacterial isolates in humans aged 5-11.
Bacillus10.4%
Staphylococcus2.6%
Citrobacter3.9%
Klebsiella7.8%
Escherichia coli36.4%
Proteus18.2%
Pseudomonas9.1%
Salmonella3.9%
Shigella7.8%
Multiple antibiotic resistance (MAR) rates recorded in children urinal bacterial species were 37.5-100% (Gram-positive) and 12.5-100% (Gram-negative),
Clinical urine tests note the color, turbidity, and odor of urine but also include urinalysis, which chemically analyzes the urine and quantifies its constituents.
A culture of the urine is performed when a urinary tract infection is suspected, as bacteriuria without symptoms doesn’t require treatment.
A microscopic examination of the urine may be helpful to identify organic or inorganic substrates and help in the diagnosis.
Clear and copious urine is generally a sign of adequate hydration.
Dark urine is a sign of dehydration.
Urine of pregnant women in the first trimester is collected and purified for the fertility hormone hCG.
Urine contains proteins and other substances that are useful for medical therapy.
Urine’s ingredients are in many prescription drugs: Urecholine.
Urine from postmenopausal women is rich in gonadotropins that can yield follicle stimulating hormone and luteinizing hormone for fertility therapy.
Urine from pregnant women contains enough human chorionic gonadotropins to produce hCG medication.
Pregnant mare urine is the source of estrogens, namely Premarin.
Urine also contains antibodies, which can be used in diagnostic antibody tests for a range of pathogens, including HIV-1.
Urine can also be used to produce urokinase, which is used clinically as a thrombolytic agent.
Urine contains large quantities of nitrogen, mostly as urea, related to quantity of protein in the diet.
Urine contains reasonable quantities of dissolved potassium.
The nitrogen content in urine is proportional to the total food protein in the person’s diet, and the phosphorus content is proportional to the sum of total food protein and vegetable food protein.
Urine’s eight main ionic species are cations Na, K, NH4, Ca and the anions, Cl, SO4, PO4 and HCO3.
Urine typically contains 70% of the nitrogen and more than half the potassium found in sewage, while making up less than 1% of the overall volume.
Nutrients excreted with urine are:
4 kg nitrogen per person per year,
0.36 kg phosphorus per person per year
1.0 kg potassium per person per year
The daily amount of urine produced by an adult is around 0.8 to 1.5 L per day
Ingesting urine tends to worsen rather than relieve dehydration due to the salts in it.
In hot weather survival situations, where other sources of water are not available, soaking cloth in urine and putting it on the head can help cool the body in a hot weather survival situation.