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Urea Nitrogen
Test CodeBUN
Alias/See Also
BUN, Blood Urea Nitrogen
Preferred Specimen
1.0 mL plasma (0.5 mL minimum)
Transport Container
PST (light green top). Red top and SST also acceptable
Specimen Stability
Room temperature: 5 days, Refrigerated: 7 days, Frozen: 45 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Grossly hemolyzed specimens are unacceptable.
Limitations
This method reacts quantitatively with ammonium ions.
Reference Range
| Plasma / Serum | Male/Female |
| Adult (>19 years): | 7 – 20 mg/dL |
| Pediatric: | |
| 0–7 days | 1-13 |
| 8 – 30 days | 1-16 |
| 1 – 3 months | 1-12 |
| 4 – 11 months | 1-14 |
| 1 – 3 years | 4-17 |
| 4 – 13 years | 6-17 |
| 14 – 19 years | 7-21 |
Clinical Significance
Serum urea nitrogen (BUN) is increased in acute and chronic intrinsic renal disease, in state characterized by decreased effective circulating blood volume with decreased renal perfusion, in postrenal obstruction of urine flow and in high protein intake states. Decreased serum urea nitrogen (BUN) is seen in high carbohydrate/low protein diet.
