CalculatorsKidneys and electrolytesBUN to creatinine ratio calculator
BUN to creatinine ratio calculator
Work out the ratio from your panel, in either unit system, and read it next to the two numbers behind it.
20.0: 1
Higher
Over about 20. Dehydration is the commonest reason. A high-protein diet, some medicines or bleeding in the gut can raise it too.
- BUN
- 18.0 mg/dLUrea 6.4 mmol/L
- Creatinine
- 0.90 mg/dL80 µmol/L
See the working
Ratio = BUN ÷ creatinine, both in mg/dL18.0 ÷ 0.90 = 20.0Read it with the two numbers themselves. A normal ratio can hide two high values.
What the ratio adds
BUN and creatinine are both cleared by the kidneys, but your body handles them differently. When you're dehydrated, the kidneys reabsorb more urea, and BUN climbs faster than creatinine. So the ratio can hint at why the numbers moved.
It's a clue, not an answer, and it always has to be read with the two values themselves.
What moves it
A higher ratio is most often dehydration. A high-protein diet, some medicines including steroids, and bleeding in the upper gut can raise it too. A lower ratio can come from a low-protein diet, overhydration, or liver problems, since the liver makes urea.
Questions
What's a normal ratio?
About 10 to 20 to 1. Sources differ a little.
I use mmol/L. Does that change it?
It would if you divided the raw numbers. Here urea and creatinine are converted first, so you get the usual ratio.
Is a high ratio dangerous?
Often it just means you need more fluid. With black or bloody stools, severe vomiting or very little urine, get seen today.
Can my ratio be normal with kidney disease?
Yes, because both numbers can be high together. That's why the ratio never stands alone.
Sources
Written by LifeFrom from the sources above, and not yet reviewed by a clinician. An estimate for your own understanding: it doesn't diagnose or treat anything, and it doesn't replace your doctor.
