Below the range
Common causes of a low Blood Urea Nitrogen (BUN)
- Liver failure
- Overhydration
- Malnutrition / low protein intake
- Pregnancy
Looking for the other direction? See what causes a high Blood Urea Nitrogen (BUN).
All tests · Kidney Function · Blood Urea Nitrogen (BUN)
Below the range
What causes a low Blood Urea Nitrogen (BUN)?
Normal range 7-20 mg/dL (2.5-7.1 mmol/L (urea) SI). Specimen: Serum or plasma. See the full Blood Urea Nitrogen (BUN) reference page for critical values and nursing considerations.
What is the normal range for Blood Urea Nitrogen (BUN)?
The standard teaching reference range for Blood Urea Nitrogen (BUN) is 7-20 mg/dL in conventional units, or 2.5-7.1 mmol/L (urea) in SI units. This value is measured in serum or plasma.
| Specimen | Serum or plasma |
|---|---|
| Conventional range | 7-20 mg/dL |
| SI range | 2.5-7.1 mmol/L (urea) |
| Critical value | > 100 mg/dL suggests serious renal impairment |
| Panel | Kidney Function |
Full details, including nursing considerations, on the Blood Urea Nitrogen (BUN) normal range page. Reference ranges vary by laboratory, method, age, sex, and population - always use the range printed on the actual result.
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