This article describes the blood and urine tests that show whether the kidneys are functioning or failing. The National Institute of Diabetes and Digestive and Kidney Diseases 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. Creatinine levels in the blood can vary, and each laboratory has its own normal range. Higher levels may be a sign that the kidneys are not working properly. As kidney disease progresses, the level of creatinine in the blood increases. As kidney function decreases, the BUN level increases.