Urea, also called carbamide, is an organic chemical compound which essentially is the waste produced when the body metabolizes protein. It is a compound not only produced by humans but also by many other mammals, as well as amphibians and some fish. Urea was the first natural compound to be synthesized artificially using inorganic compounds— a scientific breakthrough.

Urea was discovered in 1773 by the French chemist Hillaire Rouelle. In 1828, just 55 years after its discovery, it became the first organic compound to be synthetically formulated, this time by a German chemist named Friedrich Wöhler, one of the pioneers of organic chemistry.

Synthetic urea is created from synthetic ammonia and carbon dioxide and can be produced as a liquid or a solid. The process of dehydrating ammonium carbamate under conditions of high heat and pressure to produce urea was first used in 1870 and is still in use today. Uses of synthetic urea are numerous and therefore production of it is high. In fact, approximately one million pounds of urea is manufactured in the United States alone each year, most of it used in fertilizers. Because the nitrogen in urea makes it water soluble, it is highly desired in this application. Urea is also used commercially and industrially to produce some types of plastics, animal feed, glues, toilet bowl cleaners, dish washing machine detergents, hair coloring products, pesticides, and fungicides. Medicinally, it is used in barbiturates, dermatological products that re-hydrate the skin, and diuretics

Naturally, urea is produced when the liver breaks down protein or amino acids, and ammonia. The kidneys then transfer the urea from the blood to the urine. Extra nitrogen is expelled from the body through urea, and because it is extremely soluble, it is a very efficient process. The average person excretes about 30 grams of urea a day, mostly through urine, but a small amount is also secreted in perspiration.

Physicians can use urea levels to detect diseases and disorders that affect the kidneys, such as acute kidney failure or end-stage renal disease (ESRD). The blood urea nitrogen (BUN) and the urine urea nitrogen (UUN) tests, which measure urea nitrogen levels in the blood and urine, are often used to assess how well a patient's kidneys are functioning. Increased or decreased urea levels, however, do not always indicate kidney problems, but instead may reflect dehydration or increased protein intake.