Blood Urea Nitrogen

(blud yoo-REE-uh NY-truh-jen) Nitrogen in the blood that comes from urea (a substance formed by the breakdown of protein in the liver). The kidneys filter urea out of the blood and into the urine. A high level of urea nitrogen in the blood may be a sign of a kidney problem. Also called BUN and urea nitrogen.

(BUN) A common blood test that can determine the level of a certain waste product , urea, in the blood.