The urea test, also known as the blood urea nitrogen (BUN) test, is a common blood test used to measure the amount of urea nitrogen present in the blood. Urea is a waste product that is produced in the liver when proteins are broken down. It is then filtered out of the blood by the kidneys and eliminated from the body through urine. The urea test is typically ordered by doctors to evaluate kidney function or to monitor the effectiveness of treatments for kidney or liver disease. Abnormal levels of urea in the blood can be indicative of various health conditions, such as kidney failure, liver disease, dehydration, or heart failure. The test is simple and relatively inexpensive, and can be conducted in most medical facilities.