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BUN (Blood Urea Nitrogen) Test

What is the BUN test?

The blood urea nitrogen (BUN) test is done to measure the amount of nitrogen in your child’s blood. The nitrogen is present in a chemical called urea. Urea is a waste product made by the body when your child digests food. Urea is carried by the blood to the kidneys, which filter the urea out of the blood and into the urine.

Why is it done?

This test is done to see how well your child’s kidneys are filtering waste from the body. This test can help diagnose and check treatment of kidney disease.

Some medicines are processed by the kidneys and can cause kidney damage as a side effect. The BUN test may be done to be sure your child has normal kidney function before your child starts taking these medicines.

This test is almost always done with another blood test called the creatinine test.

How do I prepare my child for this test?

  • Your child may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your healthcare provider knows about any medicines, herbs, or supplements that your child is taking. Ask your provider before stopping any of your child’s regular medicines.
  • Talk to your healthcare provider if you have any questions.

How is the test done?

Having this test will take just a few minutes. A small amount of blood is taken from a vein in your child’s arm with a needle. In younger children, this test can be done with a finger prick or heel stick.

What does the test result mean?

Your child’s BUN level may be higher than normal because:

  • Your child’s kidneys aren't working well.
  • Your child has not been drinking enough fluids to replace fluid lost through blood loss, sweat, or urine.
  • Your child has been eating a high-protein diet.
  • Your child has bleeding into the stomach or intestine (from an ulcer, for example).
  • Your child has heart failure.
  • Your child is in shock from burns or an accident.
  • Your child has something blocking the flow of urine, such as by a mass inside the belly or from some problem your child was born with.
  • Your child is taking a medicine that affects the BUN level.

If your child is not sick, a BUN level lower than normal is, in general, not a cause for concern. If your child is sick, and the BUN is lower than normal, it may mean:

  • Your child’s liver isn't working well.
  • Your child is not getting the nutrients your body needs.
  • Your child has very little muscle mass.

What if my child’s test result is not normal?

Test results are only one part of a larger picture that takes into account your child’s medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your child’s health care provider about your child’s result and ask questions, such as:

  • If your child needs additional tests
  • What kind of treatment your child may need
  • What lifestyle, diet, or other changes your child might need to make
Developed by RelayHealth.
Pediatric Advisor 2014.1 published by RelayHealth.
Last modified: 2014-02-03
Last reviewed: 2014-02-03
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©2014 McKesson Corporation and/or one of its subsidiaries. All rights reserved.
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