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besure77 eNotes educator| Certified Educator

BUN stands for blood urea nitrogen. It is a test that a doctor orders when he or she she is looking at kidney and liver function. Urea is waste that is found in the blood. It is the responsibility of the kidneys to filter this waste product out of the blood. If urea quantities are high then it may indicate that the kidneys are not doing their job properly. If urea quantities are low then it may indicate that the liver is diseased or damaged. People who are on kidney dialysis frequently have their BUN levels checked to make sure that dialysis is working as it should. Many times when BUN levels are checked, creatinine levels are checked as well. Creatinine is another waste product in the blood and when these levels are high it may also indicate damage to the kidneys.

dano7744 eNotes educator| Certified Educator

BUN is a blood test that helps to evaluate renal function and hydration status. It measures the nitrogen fraction of urea, protein intake, and the ability of the kidneys to excrete waste products.

Increased BUN levels may indicate renal system disease involving one or both kidneys, ischemia (decreased blood flow to one or both kidneys), renal artery stenosis, dehydration with normal anatomy, increased protein intake, or urinary tract obstruction as with renal calculi, thrombus, or tumor. Hydronephrosis and pyelonephritis may also elevate the BUN.

The test is performed after collecting a single blood tube from the patient via venipuncture.