BUN

Background

• Blood urea nitrogen; byproduct of protein metabolism cleared by the kidneys

Normal Values

• Normal: 7-20 mg/dL

Interpretation

• Elevated BUN: renal failure, dehydration, GI bleeding (digested blood is a protein load), high-protein diet, catabolic states
• BUN:creatinine ratio >20:1 suggests prerenal azotemia or upper GI bleeding
• BUN:creatinine ratio <10:1 suggests liver disease, malnutrition, or rhabdomyolysis
• BUN is less specific than creatinine for kidney function

See Also

• Creatinine
• Acute kidney injury
• BMP