A crystalline substance with the chemical formula CO(NH2)2. It is the chief waste product discharged from the body in URINE, being formed in the liver and carried to the kidneys in the blood. The average amount excreted daily by a healthy adult on a mixed diet is about 33–35 grams. Kidney failure causes a rise in the concentration of urea in the blood (see URAEMIA; KIDNEYS, DISEASES OF). Thus, its blood level offers a guide to renal function although not as accurately as the level of CREATININE and more sophisticated investigations (such as CREATININE CLEARANCE) are needed to further define the degree of renal impairment.

Urea is rapidly changed, by a yeast-like micro-organism, into carbonate of ammonia – the cause of the ammonia smell associated with INCONTINENCE and inadequately cleaned toilets.

Urea is used as a cream in the treatment of certain skin diseases characterised by a dry skin.