Creatinine and Creatinine Clearance

Blood Creatinine

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicines, such as methyldopa (Aldomet), trimethoprim (Proloprim, Trimpex), vitamin C (ascorbic acid), cimetidine (Tagamet), some diuretics, and cephalosporin antibiotics, especially cefoxitin (Mefoxin). These affect the blood creatinine levels.
• Taking medicines, such as vitamin C (ascorbic acid), phenytoin (Dilantin), some cephalosporin antibiotics, captopril, aminoglycosides (Garamycin), trimethoprim (Proloprim, Trimpex), cimetidine (Tagamet), quinine, quinidine (Cardioquin, Quinaglute, Quinidex), procainamide, and the antifungal medication amphotericin B. These affect the creatinine clearance levels.
• Taking medicines, such as cimetidine (Tagamet), steroids, and tetracycline antibiotics. These can affect the BUN-to-creatinine ratio.
• Doing strenuous exercise 2 days before creatinine clearance test.
• Eating more than 8 oz (227 g) of meat, especially beef, in the 24 hours before a blood creatinine test and during a creatinine clearance urine test.

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Author:	Jan Nissl, RN, BS	Last Updated: August 21, 2006
Medical Review:	Patrice Burgess, MD - Family Medicine
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