A blood urea nitrogen (BUN) test measures the amount of nitrogen in
your blood that comes from the waste product urea. Urea is formed when protein
is broken down in your body. It is made in the liver and removed from your body
A BUN test is done to tell how well your kidneys are working. If
your kidneys are not able to remove urea from the blood normally, your BUN
level increases. Heart failure, dehydration, certain medicines, intestinal
bleeding, or a diet high in protein also can increase your BUN level. Liver
disease or damage can decrease your BUN level, because urea is made in the
liver. A decreased BUN level can occur normally in the second or third
trimester of pregnancy.
How this information was developed to help you make better health decisions.