Standard Operating Procedure: Blood Urea / BUN
1. Purpose: Evaluate renal function and nitrogen metabolism.
2. Specimen: Serum or plasma (heparin). Avoid hemolyzed samples.
3. Reagents: Urease-GLDH (Glutamate Dehydrogenase) kinetic reagent.
4. Procedure:
- Urease hydrolyzes urea to ammonia and CO2.
- Ammonia + α-ketoglutarate + NADH → Glutamate + NAD+ (via GLDH).
- Measure the decrease in NADH absorbance at 340 nm kinetically.
5. Reference Ranges
- The canonical adult BUN reference interval is shown in the Reference Ranges panel below.
- Urea equivalent: 15-40 mg/dL (2.5-6.7 mmol/L) when reporting as urea.