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Urea nitrogen - urine

Definition

Urine urea nitrogen is a measure of protein breakdown in the body. A test can be done to measure the amount of urea in the urine.

Alternative Names

Urine urea nitrogen

How the test is performed

A 24-hour urine sample is needed.

• 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.

For an infant, 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, place the entire penis in the bag and attach the adhesive to the skin. For females, place the bag over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts -- lively infants can move the bag, causing the urine to be absorbed by the diaper. Check the infant frequently and change the bag after the infant has urinated into it. Drain the urine from the bag into the container provided by your health care provider.

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 needed. If the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel

The test involves only normal urination, and there is no discomfort.

Why the test is performed

This test is mainly used to determine a person's protein balance and the amount of dietary protein needed by severely ill patients. It is also used to determine how much protein a person takes in.

Urea is excreted by the kidneys, so excretion of urea can reflect kidney function.

Normal Values

Normal values range from 12 to 20 grams per 24 hours.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Low levels usually indicate:

• Malnutrition (inadequate protein in diet)
• Kidney problems

High levels usually indicate:

• Too much protein intake
• Increased protein breakdown in the body

What the risks are

There are no risks.

Special considerations

References

Bazari H. Approach to the patient with renal disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 115.