Blood Urea Nitrogen (BUN)

What is a BUN (Blood Urea Nitrogen) test? Urea is the final breakdown product of the amino acids found in the protein. Nitrogen in the form of ammonia is produced in the liver when the protein is broken down. The nitrogen combined with the other chemicals in the liver from the waste product – urea. The urea is released into the bloodstream and carried to the kidneys, where it is filtered out of the blood and excreted in the form of urine.