Sign in →

Test Code LAB140 Urea Nitrogen (BUN), Blood

Additional Codes

LAB2400-Pre Dialysis BUN 

LAB2401-Post Dialysis BUN

Performing Laboratory

St. Louis Children's Hospital Laboratory - Chemistry

Specimen Requirements

Note: This test is also available as part of LAB17, Comprehensive Metabolic Panel (CMP); LAB15, Basic Metabolic Panel (BMP); and LAB19, Renal Function Panel. See Common Panel Test Combinations to avoid duplicate requests if needed.

 

Patient Preparation: None

Collection Container/Tube:

Preferred: Mint green-top Lithium Heparin (MNTGRN LiHep) tube

Acceptable: Green samplette/microtainer, plain red-top tube, or Gold SST gel tube

Submission Container/Tube: If specimen is coming from outside facility and collected in a microtainer or plain red-top tube aliquot processed sample into a plastic vial for transport (labeling with specimen type).

Specimen Collection Volume: 1.0 mL (minimum 0.6 mL)

Special Instructions: None

Sample Rejection

Mislabled or unlabeled specimens

Logistics

Test Availability: Monday-Sunday

Cut-off time: None, performed as received

Turnaround Time: Same Day; 2 hours from receipt in performing lab

Reference Values

Reference Interval: 

<2 weeks: 2-24 mg/dL
2 wks-1 year: 3-20 mg/dL
≥ 1 years: 6-25 mg/dL                                                            

Critical Value: None established

 

Methodology

Kinetic test (with Urease and Glutamate Dehydrogenase) measured photometrically

Limitations

  • In very rare cases gammopathy, in particular type IgM (Waldenstrom's macroglobulinemia) may cause unreliable results.
  • Ammonium ions may cause erroneously elevated results.

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: Centrifuge to separate. If specimen is collected in microtainer or plain red-top tube aliquot sample into a Roche false-bottom tube for testing (labeling aliquot with specimen type).

Processed Volume: 0.3 mL plasma/serum

Analyte Stability:

Specimen Type Temperature Time
Whole Blood (unprocessed)  Ambient 8 hours   
Plasma/Serum (processed) Refrigerated (preferred) 5 days 
  Ambient  1 day
  Frozen  6 months   

Test Classification and CPT Code

84520

LOINC

BUN: 3094-0

BUN Pre: 11065-0

BUN Post: 11064-3

Last Reviewed

06/2025