Blood Urea Nitrogen: normal range and what it means
Short answer: The normal blood urea nitrogen range is 7 – 20 mg/dL for adults. In SI units that is about 2.5 – 7.1 mmol/L. Labs differ a little, so also check the range printed on your report.
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Where does your blood urea nitrogen sit?
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Calculators that use your blood urea nitrogen
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Information, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell.
A nitrogen waste product reflecting kidney function and hydration.
Normal range
Adult reference range.
- Low< 7 mg/dL
- Normal7 – 20 mg/dL
- High≥ 20 mg/dL
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.
Worked out in your browser. Nothing you type is sent or saved.
A pointer, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell.
What it measures
Blood urea nitrogen, a waste product from protein breakdown that the kidneys clear. It rises with dehydration and a high protein intake as well as with kidney trouble.
What moves it
Protein intake, hydration and kidney filtration. Dehydration alone can lift it well above range.
How to bring it into range
Read it with creatinine and eGFR. The ratio between BUN and creatinine often points to dehydration rather than to the kidneys.
How fast it responds
Days.
Also reported as: bun · urea nitrogen
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Common questions
- What is the normal blood urea nitrogen range?
- The normal blood urea nitrogen range is 7 – 20 mg/dL for adults. In SI units that is about 2.5 – 7.1 mmol/L. Labs differ a little, so also check the range printed on your report.
- What does a high Blood Urea Nitrogen mean?
- A value above the reference band means Blood Urea Nitrogen is outside the range typical for a healthy adult. A single reading is rarely conclusive on its own — what matters is the trend across draws and the other markers around it, which is why HealthOS reads the whole panel together rather than one number at a time.
- How do I improve my Blood Urea Nitrogen?
- Read it with creatinine and eGFR. The ratio between BUN and creatinine often points to dehydration rather than to the kidneys.
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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.