Blood Urea Nitrogen SERUM Detail

Blood Urea Nitrogen (BUN) is a laboratory test that measures the amount of nitrogen in the blood in the form of urea, a waste product of protein metabolism.

Description

BUN reflects how well the kidneys are functioning and, to some extent, the protein metabolism in the body. Urea is produced in the liver from the breakdown of proteins and is transported in the blood to the kidneys, where it is excreted in urine.

Since BUN measures the nitrogen portion of urea, it is slightly different from total serum urea, but both are used to evaluate renal function.

Clinical Significance

• High BUN levels may indicate:

  • Kidney disease or acute/chronic renal failure

  • Dehydration

  • High protein diet

  • Heart failure

  • Gastrointestinal bleeding

• Low BUN levels may indicate:

  • Severe liver disease (reduced urea production)

  • Malnutrition

  • Overhydration

BUN is often interpreted along with serum creatinine to assess kidney function. The BUN-to-creatinine ratio can help differentiate causes of kidney dysfunction.

Normal Range

• BUN: 7–20 mg/dL (may vary slightly by laboratory)