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.

A measurement of creatinine in your blood or urine provides clues to help your doctor determine how well the kidneys are working.