A blood urea nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is made in the liver and passed out of your body in the urine. If your kidneys are not able to remove urea from the blood normally, your BUN level rises. Dehydration can also make your BUN level higher.
A BUN test may be done with a blood creatinine test. The level of creatinine in your blood also tells how well your kidneys are working. A high creatinine level may mean your kidneys are not working properly. BUN and creatinine tests can be used together to find the BUN-to-creatinine ratio.
Why is this test done?
A BUN test is done to:
See if your kidneys are working normally.
See if your kidney disease is getting worse.
See if treatment of your kidney disease is working.
Check for severe dehydration. Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to go up.
How do you prepare for the test?
Do not eat a lot of meat or other protein in the 24 hours before having a BUN test.
How is the test done?
A health professional uses a needle to take a blood sample, usually from the arm.
What happens after the test?
You will probably be able to go home right away.
You can go back to your usual activities right away.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.
Clinical Review Board All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
Clinical Review Board All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use and Privacy Policy.
The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.
Sign out
