What does a high BUN:creatinine ratio mean?

Dear Ask The Doctor:  Hello, I am 42 years old. I recently got a BUN (Blood Urea-Nitrogen) level of 18 and a creatinine level of 0.6 mgperDL. But my BUN over creatinine ratio was 30. As per my research results, this might be an indication of prerenal failure. Would you please clarify what all this mean? Should I be concerned and visit a specialist? Should I have more tests done? I'm unemployed, without a health insurance, so I would like to avoid any unnecessary costs. Thank you, VA

Dear Patient:  BUN: creatinine ratio is a crude measurement of acute renal failure. However, acute renal failure happens when there is decreased blood flow to the kidneys (e.g. dehydration, intake of high blood pressure meds like ACE inhibitors and diuretics – meds that make you pee a lot, severe bleeding, overuse of over-the-counter pain relievers like Ibuprofen, high grade fevers, etc.). This is rapidly reversible when the cause can be identified. In some cases, it is usually dehydration. Simply drinking lots of water will correct the abnormality. I really do not think there is need for you to worry since you have not mentioned any concurrent diseases with maintenance medications (hypertension, etc). If you also had a urine test done, a specific gravity of >1.020 would be suggestive of acute pre-renal failure. The most sensitive values to detect pre-renal failure are fractional excretion of sodium and renal failure index. Both values are computed after getting the blood sodium and creatinine, and urinary sodium and creatinine. In your case, I think a repeat blood test would suffice. If you have hydrated well enough and the BUN: creatinine ratio will turn out normal, then there you are fine. I do hope this helps and take care always.

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