(ū-rē′ă)
[Pronunciation]
[Gr. ouron, urine]

The diamide of carbonic acid, a crystalline solid having the formula CH₄N₂O; found in blood, lymph, and urine.
It is formed in the liver from ammonia derived from the deamination of amino acids.

Urea is the chief nitrogenous constituent of urine and, along with carbon dioxide, the final product of protein metabolism in the body. In normal conditions, urea represents 80% to 90% of the total urinary nitrogen. It is odorless and colorless, appears as white prismatic crystals, and forms salts with acids. The amount of urea excreted varies directly with the amount of protein in the diet. Its excretion is increased in fever, diabetes, or increased activity of the adrenal gland, and decreased in kidney failure.