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Creatinine and Creatinine Clearance

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BUN-to-creatinine ratio 1


6–25, with 15.5 being the best value


High values

  • High creatinine blood levels can be caused by:
    • Serious kidney damage or chronic kidney disease. Kidney damage can be caused by a life-threatening infection, shock, cancer, or low blood flow to the kidneys.
    • Dehydration.
    • Muscle injury and conditions. These include crush injuries, burns, rhabdomyolysis, muscular dystrophy, polymyositis, and strenuous exercises.
    • Shock. This is low blood pressure with many causes including severe bleeding and very severe infection.
  • High creatinine clearance levels can be caused by carbon monoxide poisoning, hypothyroidism, and pregnancy.
  • High BUN-to-creatinine ratios occur with sudden (acute) kidney failure. This may be caused by shock or severe dehydration. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract camera.gif.

Low values

  • Low blood creatinine levels can mean lower muscle mass caused by a disease, such as muscular dystrophy, or by aging. Low levels can also mean some types of severe liver disease or a diet very low in protein. Pregnancy can also cause low blood creatinine levels.
  • Low creatinine clearance levels can mean you have chronic kidney disease or serious kidney damage. Kidney damage can be from conditions such as a life-threatening infection, shock, cancer, low blood flow to the kidneys, or urinary tract blockage. Other conditions, such as heart failure and dehydration, can also cause low creatinine clearance levels.
  • Low BUN-to-creatinine ratios may be linked with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH sometimes occurs with lung disease, cancer, diseases of the central nervous system, or the use of certain medicines.

What Affects the Test

You may not be able to have the test, or the results may not be helpful, if:

  • You take certain medicines, such as:
    • The antifungal medicine amphotericin B, cimetidine (Tagamet), phenytoin (Dilantin), quinine, quinidine, procainamide, methyldopa, trimethoprim (Proloprim, Trimpex), or vitamin C (ascorbic acid).
    • Cephalosporin antibiotics, especially cefoxitin (Mefoxin), tetracycline antibiotics, and some diuretics.
  • You do some strenuous exercise 2 days before a creatinine clearance test.
  • You eat more than 8 oz (227 g) of meat, especially beef, in the 24 hours before a blood creatinine test or during a creatinine clearance urine test.
  • You don't collect your urine for exactly 24 hours.

WebMD Medical Reference from Healthwise

Last Updated: November 14, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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