Urine (from Latin Urina,ae,f.) is a liquid by-product of the body secreted by the kidneys through a process called urination (or micturition) and excreted through the urethra.

Cellular metabolism generates numerous by-products,many rich in nitrogen,that require clearance from the bloodstream.These by-products are eventually expelled from the body during urination,the primary method for excreting water-soluble chemicals from the body.These chemicals can be detected and analyzed by urinalysis.

Human urine together with human feces are collectively referred to as human waste or human excreta.

Source of medications
Urine contains proteins and other substances that are useful for medical therapy and are ingredients in many prescription drugs (e.g.,Ureacin,Urecholine,Urowave).Urine from postmenopausal women is rich in gonadotropins that can yield follicle stimulating hormone and luteinizing hormone for fertility therapy.One such commercial product is Pergonal.

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.Urine also contains antibodies,which can be used in diagnostic antibody tests for a range of pathogens,including HIV-1.

Urine contains large quantities of nitrogen (mostly as urea),as well as significant quantities of dissolved phosphates and potassium,the main macronutrients required by plants,The exact composition of nutrients in urine varies with diet.

Undiluted urine can chemically burn the roots of some plants which is why it is usually applied diluted with water,which also reduces odour development during application.When diluted with water (at a 1:5 ratio for container-grown annual crops with fresh growing medium each season,or a 1:8 ratio for more general use),it can be applied directly to soil as a fertilizer.The fertilization effect of urine has been found to be comparable to that of commercial fertilizers with an equivalent NPK rating.Concentrations of heavy metals such as lead,mercury,and cadmium,commonly found in solid human waste,are much lower in urine.The more general limitations to using urine as fertilizer then depend mainly on the potential for buildup of excess nitrogen (due to the high ratio of nitrogen),and inorganic salts such as sodium chloride,which are also part of the wastes excreted by the renal system.The degree to which these factors impact the effectiveness depends on the term of use,salinity tolerance of the plant,soil composition,addition of other fertilizing compounds,and quantity of rainfall or other irrigation.

Urine can also be used safely as a source of complementary nitrogen in carbon-rich compost.

Urine typically contains 70% of the nitrogen and more than half the phosphorus and potassium found in urban waste water flows,while making up less than 1% of the overall volume.If urine is to be collected for use as a fertiliser in agriculture,then the easiest method of doing so is with sanitation systems that utilise waterless urinals,urine-diverting dry toilets (UDDTs) or urine diversion flush toilets.Thus far,source separation,or urine diversion systems have been implemented in South Africa,China,Sweden and many other countries.

"Urine management" is a relatively new way of closing the cycle of agricultural nutrient flows (also called ecological sanitation or ecosan) and - possibly - reducing sewage treatment costs and ecological consequences such as eutrophication resulting from the influx of nutrient rich effluent into aquatic or marine ecosystems.The risks of using urine as a natural source of agricultural fertilizer are generally regarded as negligible or acceptable.

It is unclear whether source separation,urine diversion,and on-site urine treatment can be made cost effective; nor whether required behavioral changes would be regarded as socially acceptable,as the largely successful trials performed in Sweden may not readily generalize to other industrialized societies.In developing countries the use of whole raw sewage (night soil) has been common throughout history,yet the application of pure urine to crops is still rare.