A 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.

Jul. 03, 2013