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Definition
By Mayo Clinic staffA common blood test, the blood urea nitrogen (BUN) test reveals important information about how well your kidneys and liver are working. A BUN test measures the amount of urea nitrogen that's in your blood.
Here's how your body typically forms and gets rid of urea nitrogen:
- Your liver produces ammonia — which contains nitrogen — after it breaks down proteins used by your body's cells.
- The nitrogen combines with other elements, such as carbon, hydrogen and oxygen, to form urea, which is a chemical waste product.
- The urea travels from your liver to your kidneys through your bloodstream.
- Healthy kidneys filter urea and remove other waste products from your blood.
- The filtered waste products leave your body through urine.
A BUN test can reveal whether your urea nitrogen levels are higher than normal, suggesting that your kidneys or liver may not be working properly.
References
- The kidneys and how they work. National Kidney and Urologic Diseases Information Clearinghouse. http://kidney.niddk.nih.gov/kudiseases/pubs/yourkidneys/. Accessed May 30, 2013.
- BUN. Lab Tests Online. http://labtestsonline.org/understanding/analytes/bun/tab/test. Accessed June 8, 2013.
- Taal MW, et al. Brenner & Rector's The Kidney. 9th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/books/about.do?about=true&eid=4-u1.0-B978-1-4160-6193-9..C2010-1-67932-1--TOP&isbn=978-1-4160-6193-9&uniqId=321553651-265. Accessed May 30, 2013.
- Inkler LA, et al. Assessment of kidney function. http://www.uptodate.com/home. Accessed May 30, 2013.
- Anderson CF (expert opinion). Mayo Clinic, Rochester, Minn. June 11, 2013.
- Castle EP (expert opinion). Mayo Clinic, Rochester, Minn. June 19, 2013.
- National Kidney Foundation. Tests to measure kidney function, damage and detect abnormalities. http://www.kidney.org/atoz/content/kidneytests.cfm. Accessed June 25, 2013.
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