What Is the Chemical Composition of Urine?

Urine is a liquid produced by the kidneys to remove waste products from the bloodstream. Human urine is yellowish in color and variable in chemical composition, but here is a list of its primary components.

Primary Components

Human urine consists primarily of water (91% to 96%), with organic solutes including urea, creatinine, uric acid, and trace amounts of enzymes, carbohydrates, hormones, fatty acids, pigments, and mucins, and inorganic ions such as sodium (Na⁺), potassium (K⁺), chloride (Cl^-), magnesium (Mg²⁺), calcium (Ca²⁺), ammonium (NH₄⁺), sulfates (SO₄^2-), and phosphates (e.g., PO₄^3-).

A Representative Chemical Composition of Urine

• Water (H₂O): 95%
• Urea (H₂NCONH₂): 9.3 g/l to 23.3 g/l
• Chloride (Cl^-): 1.87 g/l to 8.4 g/l
• Sodium (Na⁺): 1.17 g/l to 4.39 g/l
• Potassium (K⁺): 0.750 g/l to 2.61 g/l
• Creatinine (C₄H₇N₃O): 0.670 g/l to 2.15 g/l
• Inorganic sulfur (S): 0.163 to 1.80 g/l

Lesser amounts of other ions and compounds are present, including hippuric acid, phosphorus, citric acid, glucuronic acid, ammonia, uric acid, and many others. Total solids in urine add up to around 59 grams per person. Note compounds you ordinarily do not find in human urine in appreciable amounts, at least compared with blood plasma, include protein and glucose (typical normal range 0.03 g/l to 0.20 g/l). The presence of significant levels of protein or sugar in urine indicates potential health concerns.

The pH of human urine ranges from 5.5 to 7, averaging around 6.2. The specific gravity ranges from 1.003 to 1.035.

Significant deviations in pH or specific gravity may be due to diet, drugs, or urinary disorders.

Table of Urine Chemical Composition

Another table of urine composition in human men lists slightly different values, as well as some additional compounds:

Chemical Elements in Human Urine

The element abundance depends on diet, health, and hydration level, but human urine consists of approximately:

• Oxygen (O): 8.25 g/l
• Nitrogen (N): 8/12 g/l
• Carbon (C): 6.87 g/l
• Hydrogen (H): 1.51 g/l

Chemicals That Affect Urine Color

Human urine ranges in color from nearly clear to dark amber, depending largely on the amount of water that is present. A variety of drugs, natural chemicals from foods, and diseases can alter the color. For example, eating beets can turn urine red or pink (harmlessly). Blood in the urine may also turn it red. Green urine may result from drinking highly colored beverages or from a urinary tract infection. Colors of urine definitely indicate chemical differences relative to normal urine but aren't always an indication of illness.

Source

• Putnam, DF. NASA Contractor Report No. NASA CR-1802. July 1971.