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Urea Nitrogen (UUN), Urine

UUN, Urine Urea Nitrogen, Urea Nitrogen, Urine

Test Codes

EPIC: LAB7480, 24-Hour Urine: EPIC: LAB449, Beaker: UNU24, Random Urine: EPIC: LAB480, Beaker: UNU

Department

Toxicology

Instructions

Note: 24-hour and random urine specimens MUST be collected separately. See below for collection criteria.

• Please refer to the Specimen Collection Manual for instructions on 24-Hour Urine or Random urine Collection:
  • Urine 24-Hour Collection - Inpatient
  • Urine 24-Hour Collection - Outpatient
  • Urine 24-Hour Collection - Outreach
  • Random Urine Collection

Specimen Collection Criteria

Collect: 24-hour urine or timed urine specimen with a 24-hour urine container with no preservatives.
Also acceptable: Random urine specimen in a screw-capped container (preferred) or another sterile collection cup. Preservatives are not acceptable for random urine specimens. (Minimum: 20 mL) 

• Refer to the table of Urine Preservative Options when multiple tests are requested.
• Keep 24-hour urine specimen iced or refrigerated during collection.
• Include start and end dates and times for the collection period on the specimen container.

Urine Preservative Options
No Preservative	6N Hydrochloric Acid	Boric Acid (10g)	Sodium Carbonate	50% Acetic Acid
PREFERRED	Acceptable	Acceptable	Unacceptable	Unacceptable

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Entire 24-hour urine collection, or random urine, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

Specimens that are not collected and processed as indicated. 

In-Lab Processing

Measure total volume of 24-hour urine specimen. Record total volume and collection start and end dates and times in the LIS system. Aliquot a minimum of 10 mL from the well-mixed 24-hour urine collection.

Storage

Specimen Stability for Testing:

Room temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 4 days
Frozen (-20°C/-4°F or below): For longer storage.

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days (An aliquot is stored for 30 days.)

Laboratory

Dearborn Chemistry Laboratory

Farmington Hills Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Troy Chemistry Laboratory

Performed

Sunday – Saturday.
Results available within 24 hours.

Reference Range

Urine Urea Nitrogen: 12,000-20,000 mg/24 hours (12-20 g/24 hours).
Normal ranges for random urines or for collections less that 24 hours have not been established.

Test Methodology

Spectrophotometry.

Interpretation

• Elevated urine urea nitrogen levels may be seen postoperatively or with increased dietary protein or hyperthyroidism.
• Decreased levels are seen in pregnancy, low protein and high carbohydrate diets, convalescence, liver disease, toxemia, and renal disease.

Clinical Utility

Urine urea nitrogen is performed as part of the Stone Former Workup to evaluate a patient for the likelihood of renal calculi formation.

CPT Codes

84540

Contacts

Last Updated

9/10/2024