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Test Code BUN Blood Urea Nitrogen

Additional Codes

Cerner

NextGen

BUN

BUN

Alternate Name(s)

BUN

Urea Nitrogen

Urea

Useful For

The major pathway of nitrogen excretion is in the form of urea that is synthesized in the liver, released into the blood, and cleared by the kidneys. Elevated serum urea nitrogen occurs in glomerulonephritis, shock, urinary tract obstruction, pyelonephritis, and other causes of acute and chronic renal failure. Severe congestive heart failure, hyperalimentation, diabetic ketoacidosis, dehydration, and bleeding from the gastrointestinal tract elevate urea nitrogen. Low urea nitrogen often occurs in normal pregnancy, with decreased protein intake, in acute liver failure, and with intravenous fluid administration.

Methodology

Colorimetric: Urease Quinolinium Dye

Patient Preparation

None

Collection Instructions

Standard phlebotomy practices.

Specimen Requirements

Container

Specimen Type

Tube

Lithium Heparin Plasma

PST

 or  or 

Serum

 or 

SST

 or  or 

 

Stability

Storage

Temperature

Stability

Room Temperature

18-28°C

≤ 1 day

If separated within 4 hours.

Refrigerated

 2-8°C

≤ 5 days

If separated within 4 hours.

Frozen

≤-18 °C

≤ 6 months

If separated within 4 hours.

Rejection Criteria

Gross Hemolysis

Result Reporting and Reference Values

Reported in mg/dL

Age

Low

High

Critical Low

Critical High

0-18Y

6

20

N/A

N/A

18-150Y

5

23

N/A

N/A

Reflex Testing

None

Limitations

  • Ortho reports the following bias: 
    • Hemoglobin at 50 mg/dl can cause a +1.1 mg/dl bias
    • Ammonium ions may cause an increased BUN/Urea value-consult IFU
  • Ortho reports no significant effect with the following:  
    • Lipemia up to 800 mg/dL
    • Bilirubin up to 40 mg/dl
  • The following interpretive data is visible to the practitioner:
    • Elevated ammonia will result in an increase in measured nitrogen.