Commonly known as creatinine, serum creatinine is a waste product that is produced by the metabolism of muscles. Creatinine is produced from creatine, a molecule that promotes energy production in muscles and is filtered from the blood by the kidneys.
A serum creatinine test is usually used to determine whether the kidneys are working properly. High level of creatinine in the blood indicates that there is a problem in the kidneys. The test may also be performed to calculate the amount of creatinine in the urine, as stated by Mayo Clinic. Abnormal results could mean muscle problem, kidney disease, dehydration or a blocked urinary tract.