Medical Tests of Kidney Function Healthy kidneys remove wastes and excess fluid from the blood.
Blood tests show whether the kidneys are failing to remove wastes.
Urine tests can show how quickly body wastes are being removed and whether the kidneys are also leaking abnormal amounts of protein. Blood Tests Serum creatinine. Creatinine levels in the blood can vary, and each laboratory has its own normal range. As kidney disease progresses, the level of creatinine in the blood increases. Some urine tests require only a few ounces of urine.