BUN
Meaning of BUN: BUN is a blood test that measures urea nitrogen, a waste product cleared by the kidneys, to help assess kidney function.
Definition of BUN
BUN, short for blood urea nitrogen, refers to the nitrogen contained within urea, a waste product formed in the liver as it breaks down protein. Urea is released into the bloodstream and normally filtered out by the kidneys, then excreted in urine.
Because urea is cleared from the blood by the kidneys, measuring BUN provides information about how well the kidneys are filtering waste from the bloodstream. A BUN level that is higher than expected can suggest reduced kidney function, though it can also rise with dehydration, a high protein diet, gastrointestinal bleeding, or certain medications, since the test reflects more than kidney function alone.
BUN is commonly measured together with creatinine, another waste product cleared by the kidneys, since comparing the two values helps determine whether an abnormal result is more likely due to a kidney problem or to another factor affecting urea production or clearance.
Also known as
Used in a sentence
BUN and creatinine were measured to evaluate the patient's kidney function.
Good to know
BUN can rise from causes unrelated to the kidneys, such as dehydration or a high protein intake, so it is generally interpreted alongside creatinine rather than on its own.