Sign in →

Test Code Billings Clinic: 4008 Urea Nitrogen (BUN), Plasma or Serum

Important Note

Blood samples from some patients with monoclonal gammopathies may produce falsely elevated results.

Performing Laboratory

Billings Clinic Laboratory: Chemistry

Useful For

  • The determination of serum blood urea nitrogen currently is the most widely used screening test for the evaluation of kidney function.
  • The test is frequently requested along with the serum creatinine test since simultaneous determination of these 2 compounds appears to aid in the differential diagnosis of prerenal, renal and postrenal hyperuremia.

Methodology

Urease with GLHD / Bichromatic Rate

Specimen Requirements

Submit only 1 of the following specimens:

Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from the time of collection.

 

Plasma

  • Draw blood in a green-top (lithium heparin) tube(s).
  • Spin down and send 0.5 mL of heparinized plasma frozen.

 

Serum

  • Draw blood in a plain, red-top tube(s) or a serum gel tube(s).
  • Spin down and send 0.5 mL of serum frozen

Storage/Stability

Specimen Type Temperature Time
Serum, Plasma Refrigerated 7 days
  Frozen (preferred) 1 month
  Ambient 5 days

 

Reject Due To

  • Gross hemolysis

Reference Values

Males:

0 - 7 days:                  3 - 25 mg/dL

7 - 31 days:                2 - 19 mg/dL

31 days - 17 years:    5 - 18 mg/dL

> 17 years:                10 - 20 mg/dL

 

Females:

0 - 7 days:                  3 - 25 mg/dL

7 - 31 days:                2 - 19 mg/dL

31 days - 17 years:    5 - 18 mg/dL

> 17 years:                 7 - 23 mg/dL

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

84520 - Urea nitrogen, quantitative

LOINC Code Information

Reporting Name LOINC Code
BUN 3094-0

 

Interferences

  • Hemoglobin at 250 mg/dL increases the UN result in serum/plasma at 9 mg/dL by 14%.
  • Conjugated bilirubin at 30 mg/dL decreases the UN result in serum/plasma at 40 mg/dL by -14%.