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:
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Your liver produces ammonia — which
contains nitrogen — after it breaks down proteins used by your
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