A common BLOOD test, the blood urea nitrogen (BUN) test reveals important information about how well your kidneys are working.

A creatinine test is a measure of how well your kidneys are performing their job of filtering waste from your BLOOD. Creatinine is a chemical compound left over from energy-producing processes in your muscles. Healthy kidneys filter creatinine out of the blood. Creatinine exits your body as a waste product in urine.