Specimen Requirements


Urea Nitrogen (BUN), 24 Hour Urine

Specimen Requirement

At the start of the 24 hour collection, discard first morning urine, from that time collect all urine for 24 hours. Record total volume of urine, mix well, then aliquot 10 mL to a screw top container. Indicate total volume of 24 hour urine on aliquot and requisition.

Total volume must be recorded for testing.


Spectrophotometry (SP)


Room temp: 24 hours (collection time), Refrigerated: 7 days, Frozen: 15 months

Reference Range

By Report*


3-4 days, set up Monday-Saturday

Clinical Use

Urea excreted in the urine is the primary method of nitrogen elimination. Conditions associated with increased urine urea nitrogen are hyperthyroidism, high protein diets and post-operative states. Decreased levels are associated with convalescence, liver disease, toxemia and advanced renal disease.

Test Code