Last updated October 10, 2026 · Report an error
Simple ratio of blood urea nitrogen (BUN) to serum creatinine, both in mg/dL — pure division. The commonly cited normal reference range is roughly 10:1 to 20:1; a higher ratio is often discussed in the context of dehydration or reduced kidney perfusion, and a lower ratio in the context of liver disease or malnutrition, but this tool performs no interpretation beyond the arithmetic. For general reference and educational purposes only — not a medical diagnosis. Consult a doctor for actual lab interpretation.
How it works
Enter BUN and serum creatinine, both in mg/dL. The tool divides BUN by creatinine and compares the result to the standard 10:1-20:1 reference range.
- Enter blood Urea Nitrogen, BUN (mg/dL).
- Enter serum creatinine (mg/dL).
- Click Calculate to see your results.
Examples
BUN 15 mg/dL, Creatinine 1.0 mg/dL
Ratio = 15 / 1.0 = 15 — within the commonly cited 10:1 to 20:1 normal range.
Who should use it
- Reviewing a basic metabolic panel result.
- Nephrology and nursing education about renal lab ratios.
Industry applications
- Nephrology and primary care reference
- Nursing education
Advantages
- Simple, standard, widely taught ratio.
- Quick reference against a commonly cited normal range.
Limitations
- No interpretation of the underlying cause.
- Affected by many non-kidney factors (diet, hydration, GI bleeding).
Common mistakes to avoid
- Confusing BUN with total serum urea (BUN is roughly half of urea by molecular weight).
- Interpreting the ratio in isolation without other kidney function labs.
Best practices
- Review the ratio alongside creatinine, eGFR, and clinical context, with a doctor.
Tips
- The BUN/Cr ratio is typically interpreted alongside the trend in creatinine itself, not as a standalone number.