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Blood Urea Nitrogen (BUN)


Based on an enzymatic reaction where urea is hydrolyzed by urease yielding ammonia and carbon dioxide. The reaction results in reducing two molecules of NADH to NAD+, which is directly proportional to the amount of BUN present in the initial sample.

Test Utility

A quantitative determination of urea nitrogen from human serum that is used for the diagnosis of certain renal and metabolic conditions.

Specimen Collection and Preparation

Serum or plasma sample in the following tubes:

  • Preferred Specimen: One Gold-top OR red top SST tube. (Minimum Whole Blood: 4.0 mL)

  • Also acceptable: One Lithium OR Sodium Heparin tube OR one Lavender-top EDTA tube. (Minimum Whole Blood: 3.0 mL)

Specimen Storage and Stability

If analysis is delayed, the sample should be refrigerated or frozen.

Specimen Stability:

  • Room Temperature (15–25°C): 24 hours

  • Refrigerated (2–8°C): 7 days

  • Frozen (-20°C or below): 60 days

Specimen Rejection

  • Insufficient sample volume

  • Sample not stored at proper temperature

  • Frozen whole blood

  • Hemolyzed samples

  • Severely lipemic specimens

  • Specimen labeled incorrectly or not labeled

Reference Pages


Monday – Saturday

Result available within 24 hours of receipt in laboratory

NOTE: Specimens are refrigerated (2-8°) for 7 days before disposal

STAT results available within 2 hours of receipt in the laboratory


Vibra Health Laboratory  

1307- A, Allen Dr 

Troy, MI 48083 

(248) 846-0663

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