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Thursday, January 29, 2015
I am a 53 year old woman with a high BUN/creatinine ratio of 35. My creatinine serum was .78 and BUN was 27. Is this highly abnormal and something I should be concerned about?
Most likely there is no cause for worry here.
BUN (blood urea nitrogen) and creatinine are waste products that are produced by normal metabolic processes in the body and by the breakdown of foods, especially those high in protein. The normal value for BUN is approximately 10-20, and for creatinine, 0.5-1.2. The ratio between the two is usually between 10:1 and 20:1.
Here are some possible explanations for a high BUN/creatinine ratio:
1) Mild dehydration: after an overnight fast, your body can become a little water-depleted, which could cause the BUN to be high.
2) High protein diet: even a high-protein meal on the day before the test may increase the BUN without affecting creatinine, so that the ratio may become elevated.
3) Heart failure or liver cirrhosis: both of these conditions can cause a high BUN/creat ratio in the absence of kidney problems.
4) GI bleeding: if there is a bleeding ulcer or bleeding of any type anywhere in the stomach or intestines, the BUN will rise disproportionately from the creatinine.
5) Steroids: in people taking high doses of steroid medications such as prednisone (for instance, for asthma), the BUN can be elevated, causing a high calculated BUN/creatinine ratio.
6) Diuretics: if you are taking these for any reason, certain ones (especially hydrochlorothiazide) can increase the BUN slightly.
So if you think that any of these conditions may apply to you, you may need a little more testing. The best thing to do is probably just to ask your doctor to repeat the tests at a time when you're not fasting and not likely to be dehydrated.
Mildred Lam, MD
Associate Professor of Medicine
School of Medicine
Case Western Reserve University