UREA, the major end product of protein catabolism in animals, is primarily produced in the liver and secreted by the kidneys. It is the primary vehicle for removal of toxic ammonia from the body. Urea determination is very useful for medical clinicians to assess kidney function of patients. In general, increased urea levels are associated with nephritis, renal ischemia, urinary tract obstruction, and certain extrarenal diseases (e.g. congestive heart failure, liver diseases, and diabetes). Decreased levels often indicate acute hepatic insufficiency, but may also result from over vigorous parenteral fluid therapy. Simple, direct and automation-ready procedures for measuring urea or blood urea nitrogen (BUN) are popular in research and drug discovery. This urea assay is designed to directly measure urea in biological samples. In this assay, urease converts urea to ammonia and carbon dioxide. NADH is then converted to NAD+ in the presence of ammonia, Alpha-ketoglutarate, and glutamate dehydrogenase. The decrease in optical density at 340 nm is directly proportional to the urea concentration in the sample.