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Date of last update: 10/09/2017.

Forum Name: Miscellaneous Nephrology Topics

Question: BUN/Creatinine Ratio

 mickapoo - Tue Jul 12, 2005 4:43 pm

Can anyone tell me what is the normal value for BUN/Creatinine ratio? I was told that a ratio of 21:1 is considered normal, while I have read online that 10:1 is normal, with ratios as high as 20:1 indicating dehydration and above indicated possible kidney failure.

With this conflicting information, I'm not sure what to believe! If there is a medical professional who can help guide me, I would greatly appreciate it.

Thank you.
 Dr. Tamer Fouad - Thu Jul 14, 2005 5:54 am

User avatar A BUN/creatinine ratio can help your health professional predict which conditions, such as dehydration, may be causing abnormal BUN and creatinine levels and decreased kidney function.
As for the normal values it depends on the age. For infants younger than 1 year the BUN/creatinine ratio normally reaches up to 1:30. For anyone older than 12 months it is normal in the range from 1:10 up to 1:20.
High BUN/creatinine ratios occur with sudden (acute) kidney failure, which may be caused by conditions such as shock or severe dehydration. An obstruction in the urinary tract (such as from a kidney stone) can cause an elevated BUN/creatinine ratio. A very high BUN/creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract.
A low BUN/creatinine ratio may be associated 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, and the use of certain medications.

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