In humans, urine is a mixture of 2-4% urea, some salts, bile pigments (coloring), poisons, drugs, and hormones. The remainder of the solution is excreted water. The exact composition of urine is dependent upon diet, level of activity, and general health. If excess water is consumed, the urine is dilute, and after exercise it is concentrated. A normal adult will produce approximately 1.5l of urine per day.

The chemistry of urine is basically that of urea and as such it has been used in the production of dyes, as a fertilizer, as a food supplement for sheep, and in the production of urea formaldehyde resins. Urine has historically been used in dyeing materials until around 1828, when the commercial production of urea was first introduced.

In alternative medicine, urine is considered a curative for a variety of medical conditions. It is believed that the first urine of the day should be consumed for health purposes. Some also advocate bathing in urine to cure skin ailments. There is no hard scientific evidence to support such practices, although when it first leaves the body urine is a sterile liquid.