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Creatinine is a breakdown product of creatine, which is an important part of muscle.
Your health care provider may ask you to temporarily stop any medicines that may affect the test results. These include antibiotics and stomach acid medicines. Be sure to tell your provider about all the medicines you take.
Do not stop taking any medicine before talking to your doctor.
The urine test involves only normal urination. There is no discomfort.
To draw blood, when the needle is inserted, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. These soon go away.
The creatinine clearance test is used to estimate glomerular filtration rate (GFR). GFR is a measure of how well the kidneys are working, especially the kidneys’ filtering units. These filtering units are called glomeruli.
Creatinine is removed, or cleared, from the body entirely by the kidneys. If kidney function is abnormal, creatinine level increases in the blood because less creatinine is released through the urine.
Clearance is often measured as milliliters/minute (ml/min). Normal values are:
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
Abnormal results (lower than normal creatinine clearance) may indicate:
Risks of the test involve the blood draw process.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
Gerber GS, Brendler CB. Evaluation of the urologic patient: history, physical examination, and urinalysis. In: Wein AJ, Kavoussi LR, Novick AC, et al., eds. Campbell-Walsh Urology. 10th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 3.
Israni AK, Kasiske BL. Laboratory assessment of kidney disease: glomerular filtration rate, urinalysis, and proteinuria. In: Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 25.
McPherson RA, Ben-Ezra J. Basic examination of urine. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 28.