BUN to creatinine ratio calculator and normal range
Short answer: The BUN to creatinine ratio is usually about 10 to 20. Above 20 most often means you were a little dehydrated or ate a lot of protein; below 10 can come with a low-protein diet, liver disease or pregnancy. It is read together with creatinine and eGFR, never on its own.
Free calculator
BUN to creatinine ratio calculator
BUN/creatinine ratio = BUN (mg/dL) ÷ creatinine (mg/dL)
Source: Hosten AO. BUN and creatinine. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Boston: Butterworths; 1990. Chapter 193.
Only matters in mg/dL
From the same blood test
Your result
Enter the numbers from your lab report to see your result.
US labs print BUN (urea nitrogen); many others print urea, which is about 2.14 times bigger in mg/dL. In mmol/L the two are the same number. The calculator converts.
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A pointer, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell.
How to read the result
- Low (below 10)< 10Lower than usual. It can come with a low-protein diet, drinking a lot of fluid, liver disease or pregnancy, and also with a high muscle mass. Read it with your creatinine and eGFR rather than on its own.
- Typical (10 to 20)10 – 20In the usual range.
- High (above 20)≥ 20Higher than usual. The most common reasons are not drinking enough, a high-protein diet, steroid tablets and bleeding in the stomach or gut. With a normal creatinine it is usually harmless. If your creatinine is raised too, or you feel unwell, talk to a doctor.
Your lab’s range
Most labs read a BUN/creatinine ratio of about 10 to 20 as usual (some print 6–22 or 12–20). In mmol/L terms that is a urea ÷ creatinine ratio of roughly 40 to 80. Your lab’s own range comes first.
How it is worked out
BUN/creatinine ratio = BUN (mg/dL) ÷ creatinine (mg/dL)
US labs print BUN (urea nitrogen); many others print urea, which is about 2.14 times bigger in mg/dL. In mmol/L the two are the same number. The calculator converts.
Source
- Hosten AO. BUN and creatinine. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Boston: Butterworths; 1990. Chapter 193.
The markers it uses
Questions
- What is a normal BUN to creatinine ratio?
- About 10 to 20 when both are in mg/dL. Some labs print slightly different ranges. In mmol/L (urea ÷ creatinine) it is roughly 40 to 80.
- How do I calculate the BUN/creatinine ratio from urea?
- In mg/dL, divide urea by 2.14 to get BUN, then divide by creatinine. In mmol/L, urea and BUN are the same number: convert creatinine from µmol/L to mg/dL (÷ 88.4) and urea from mmol/L to BUN mg/dL (× 2.8). The calculator does this for you.
- What does a high BUN/creatinine ratio mean?
- Most often dehydration or a high-protein diet; also steroid tablets, a stomach or gut bleed, or reduced blood flow to the kidneys. If creatinine is normal and you feel fine, drink well and recheck. If creatinine is high too, or you feel unwell, see a doctor.
More calculators for the same system
A pointer, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell. Reference ranges are general-population guidance compiled from common clinical laboratories, not a diagnosis. Lab-to-lab ranges differ. Always read your results with your doctor.