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.

Blood Tests

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.

Urine Tests

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.

Creatinine Clearance

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

Additional Information on Medical Tests of Kidney Function

The National Kidney and Urologic Diseases Information Clearinghouse collects resource information on kidney and urologic diseases for the Combined Health Information Database (CHID). CHID is a database produced by health-related agencies of the Federal Government. This database provides titles, abstracts, and availability information for health information and health education resources.

To provide you with the most up-to-date resources, information specialists at the clearinghouse created an automatic search of CHID. To obtain this information you may view the results of the automatic search on Medical Tests of Kidney Function.

Or, if you wish to perform your own search of the database, you may access the CHID Online web site and search CHID yourself.

National Kidney and Urologic Diseases Information Clearinghouse

3 Information Way
Bethesda, MD 20892-3580
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.

Publications produced by the clearinghouse are carefully reviewed for scientific accuracy, content, and readability.

This e-text is not copyrighted. The clearinghouse encourages users of this e-pub to duplicate and distribute as many copies as desired.

NIH Publication No. 99-4623