BUN, Serum

Message

Test performed at York Hospital Laboratory.

Test Code

BUN

Alias/See Also

Urea Nitrogen

CPT Codes
84520

Preferred Specimen

0.2 mL serum collected in a serum separator tube (SST)

Other Acceptable Specimens

0.2 mL serum collected in a no additive (red-top) tube, transferred to a plastic screw-cap vial
0.2 mL plasma collected in a lithium heparin (green-top) gel separator tube

Transport Temperature

Refrigerated

Specimen Stability

Room temperature: 24 hours
Refrigerated: 5 days
Frozen: 6 months

Methodology
Colorimetric

Setup Schedule

Daily

Report Available

Next Day
Available STAT 1/2 Hour

Reference Range

Age	BUN (mg/dL)
<3 Years	5 - 17
4-13 Years	7 - 17
14-19 Years	8 - 21
Adult	7 - 23

Critical Values
>80 mg/dL

Clinical Significance

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. A high 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.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.