Urea Nitrogen, 24-Hour Urine

CPT: 84540
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Test Details


  • BUN
  • Nitrogen Balance Study
  • Urine Urea Nitrogen


Renal function test; coarse nitrogen-wasting test on patients on hyperalimentation; indicate nitrogen balance in hyperalimentation; rule out tap of urinary bladder in amniocentesis, paracentesis



Reference Interval

12−20 g/24 hours

Specimen Requirements


Urine (24-hour)


10 mL aliquot of entire collection

Minimum Volume

1 mL aliquot


Plastic urine container, no preservative


Refrigerate the specimen as it is collected. Instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Container must be labeled with patient's full name, date and time collection started, and date and time collection finished.

Storage Instructions

Room temperature

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Improper labeling

Clinical Information

Special Instructions

Record total 24-hour urine volume on the request form.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
003541 Urea Nitrogen, 24-Hour Urine 013508 Urea Nitrogen, U mg/dL 12967-6
003541 Urea Nitrogen, 24-Hour Urine 013236 Urea Nitrogen, 24hr g/24 hr 3096-5

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