Medical Tests of Kidney Function
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.
Serum creatinine. Creatinine (kree-AT-uh-nin) is a waste product that comes from meat protein in the diet and also comes from the normal wear and tear on muscles of the body. Creatinine levels in the blood can vary, and each laboratory has its own normal range. In many labs the normal range is 0.6 to 1.2 mg/dL. 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.
Blood urea nitrogen (BUN). Urea nitrogen (yoo-REE-uh NY-truh-jen) also is produced from the breakdown of food protein. A normal BUN level is between 7 and 20 mg/dL. As kidney function decreases, the BUN level increases.
Some urine tests require only a few ounces of urine. But some tests require collection of all urine produced for a full 24 hours. A 24-hour urine test shows how much urine your kidneys produce in 1 day. The test also can give an accurate measurement of how much protein leaks from the kidney into the urine in 1 day.
A creatinine clearance test compares the creatinine in a 24-hour sample of urine to the creatinine level in the blood, to show how many milliliters of blood the kidneys are filtering out each minute (mL/min).
More information is available from
American Kidney Fund
6110 Executive Boulevard
Rockville, MD 20852
(800) 638. 8299
National Kidney Foundation
30 East 33rd Street
New York, NY 10016
(800) 622. 9010
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E-mail: National Kidney and Urologic Diseases Information Clearinghouse
The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S. Department of Health and Human Services. Established in 1987, the clearinghouse provides information about diseases of the kidneys and urologic system to people with kidney and urologic disorders and to their families, health care professionals, and the public. NKUDIC answers inquiries; develops, reviews, and distributes publications; and works closely with professional and patient organizations and Government agencies to coordinate resources about kidney and urologic diseases.
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NIH Publication No. 99-4623