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Urea Nitrogen

Test ID: A887

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Urea is a waste product from the breakdown of proteins within the body. Usually urea is removed from the body by the kidneys. Urea nitrogen refers to the nitrogen content of urea. Measurements of urea nitrogen in a blood sample are useful for the evaluation of kidney function and metabolic health. Urea nitrogen levels are commonly measured in conjunction with creatinine to assess renal function.



How to order a test


  • Blood Urea Nitrogen
  • BUN

What is Included?

Measurement of urea nitrogen levels in a blood sample by enzymatic (urease) methodology.

Turnaround Time

1 – 3 business days
The turnaround time is not guaranteed. The average turnaround time is 1 – 3 business days from the date that the sample arrives at the laboratory. Shipping time for the sample is not included. Additional time is required if the case requires confirmatory or reflex testing, or if the sample is insufficient, or if a recollection is required.

Related Documents

Additional Information and Resources


Preparation Before Specimen Collection

No fasting is required prior to collecting the blood sample for this test. However, it is recommended that you avoid consumption of a high protein meal or drink in the 12 hours prior to collecting your blood sample.

Specimen Type



50 μL in a microtainer


Microtainer (regular blood tube)

Collection Method

This test requires a blood sample from a finger prick. All supplies for sample collection are provided in the kit.

  1. First wash and dry hands. Warm hands aid in blood collection.
  2. Clean the finger prick site with the alcohol swab and allow to air dry.
  3. Use the provided lancet to puncture the skin in one quick, continuous and deliberate stroke.
  4. Wipe away the first drop of blood.
  5. Massage hand and finger to increase blood flow to the puncture site. Angle arm and hand downwards to facilitate blood collection on the fingertip.
  6. Drip blood into the microtainer tube.
  7. Dispose of all sharps safely and return sample to the laboratory in the provided prepaid return shipping envelope.

NOTES: Avoid squeezing or ‘milking’ the finger excessively. If more blood is required and blood flow stops, perform a second skin puncture on another finger. Do not touch the fingertip.

Specimen Storage

Maintain specimen at temperatures between 2°C and 30°C during storage and transport.

Specimen Stability

Blood samples can be refrigerated or kept at room temperature for up to 7 days.

Causes for Rejection

  • Incorrect or incomplete patient identification
  • Incorrect specimen collection
  • Inappropriate storage and transport conditions
  • Incorrect specimen volume



To measure urea nitrogen levels in a blood sample for the evaluation of kidney function and metabolic health. Urea nitrogen levels are commonly measured in conjunction with creatinine to assess renal function.


  • This report is not intended for use in medico-legal applications. 
  • These results should be interpreted in conjunction with other laboratory and clinical information.
  • Correct specimen collection and handling is required for optimal assay performance. 
  • Interferences from medication or endogenous substances may affect results.
  • Borderline high values may occur after recent ingestion of a high protein meal.
  • Low urea nitrogen levels occur during normal pregnancy, with intravenous fluids, and with some antibiotics.


Enzymatic (urease) (Alinity c Urea Nitrogen assay)

Reference Intervals

  Urea Nitrogen Range in serum/plasma (mg/dL) Urea Range in serum/plasma


1 – 3 years 5.1 – 16.8 1.8 – 6.0
4 – 13 years 7.0 – 16.8 2.5 – 6.0
14 – 19 years 8.4 – 21.0 3.0 – 7.5
Adult Male < 50 years 8.9 – 20.6 3.2 – 7.4
Adult Male > 50 years 8.4 – 25.7 3.0 – 9.2
Adult Female < 50 years 7.0 – 18.7 2.5 – 6.7
Adult Female > 50 years 9.8 – 20.1 3.5 – 7.2

These reference ranges were obtained from the Alinity c Urea Nitrogen package insert. (Source: Thomas L. Clinical Laboratory Diagnostics: Use and Assessment of Clinical Laboratory Results. Frankfurt/Main, Germany: TH-Books Verlagsgesellschaft mbH; 1998:374–377.)