Blood Urea Nitrogen: normal range and what it means
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
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 a normal Blood Urea Nitrogen level?
- Normal: 7 – 20 mg/dL. Adult reference range.
- 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.