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How can the bun/creatinine ratio show dehydration?

4 doctors weighed in
Dr. Michael Taylor
Critical Care
3 doctors agree

In brief: BUN/Cr > 20:1

Urea (BUN) is reabsorbed by the kidney; creatinine is not.
In dehydration, as water decreases and urea is reabsorbed, the BUN rises. Eventually, the cr will rise, too (if dehydration continues), but it doesn't increase in magnitude as fast as the bun. The bun/cr ration is usually ~10:1...When it's greater than 20:1, this suggests dehydration.

In brief: BUN/Cr > 20:1

Urea (BUN) is reabsorbed by the kidney; creatinine is not.
In dehydration, as water decreases and urea is reabsorbed, the BUN rises. Eventually, the cr will rise, too (if dehydration continues), but it doesn't increase in magnitude as fast as the bun. The bun/cr ration is usually ~10:1...When it's greater than 20:1, this suggests dehydration.
Dr. Michael Taylor
Dr. Michael Taylor
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