Urine urea nitrogen

Alternative names
UUN; Urea nitrogen - urine

A urea nitrogen urine test measures the amount of urea in the urine.

How the test is performed
A 24-hour urine sample is needed.
The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

  • On day 1, urinate into the toilet when you get up in the morning.  
  • Afterwards, collect all urine in a special container for the next 24 hours.  
  • On day 2, urinate into the container when you get up in the morning.  
  • Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

Thoroughly wash the area around the urethra. Open a Urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts - lively infants can displace the bag, causing the specimen to be absorbed by the diaper. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

How to prepare for the test
No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel
Urinate in the normal manner, but collect all the urine in the container provided.

Why the test is performed
This test is mainly used to assess the protein balance and the amount of dietary protein needed by severely ill patients. Urine urea serves this purpose as it is a measure of protein breakdown in the body.

Urea is excreted by the kidneys, so excretion of urea can reflect kidney function. The urine urea excretion can be measured to obtain a ratio between the plasma (blood) urea and the urine urea. This ratio (U/P urea) is an indicator of how well the kidneys are able to filter and excrete urea from the bloodstream.

Normal Values
Normal values range from 6 to 17 gm/24 hours or (60 to 90 mg/dl). Normal value ranges may vary slightly among different laboratories.

Note: gm/24 hours = grams per 24 hours; mg/dl = milligrams per deciliter

What abnormal results mean

Abnormal results are indicated as follows:

Low levels usually indicate:

  • Malnutrition (inadequate protein in diet)  
  • Kidney dysfunction  
  • Increased reabsorption

High levels usually indicate:

  • Excessive protein intake  
  • Increased protein breakdown in the body

What the risks are
There are no risks associated with testing urine urea.

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

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