This article is from the Interpretation Of Lab Test Profiles, by Ed Uthman uthman@neosoft.com with numerous contributions by others.
Serum urea nitrogen (BUN) is increased in acute and chronic
intrinsic renal disease, in states characterized by decreased
effective circulating blood volume with decreased renal
perfusion, in postrenal obstruction of urine flow, and in high
protein intake states.
Decreased serum urea nitrogen (BUN) is seen in high
carbohydrate/low protein diets, states characterized by
increased anabolic demand (late pregnancy, infancy, acromegaly),
malabsorption states, and severe liver damage.
In Europe, the test is called simply "urea."
 
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