What is the normal range for the blood urea nitrogen (BUN) level in most adults?

What is the normal range for the blood urea nitrogen (BUN) level in most adults?

• A. 5-15 mg/dL
• B. 10-20 mg/dL
• C. 15-25 mg/dL
• D. 20-30 mg/dL

Answer: (B)

BUN measures the amount of nitrogen waste (urea) in the blood, a byproduct of protein metabolism that is filtered by the kidneys. In healthy adults, the reference values fall within a mid-range span used by most laboratories. Values within this mid-range are considered normal, while higher numbers can indicate dehydration, high protein intake, or reduced kidney function, and lower numbers can be seen with liver problems, malnutrition, or overhydration. Because BUN can vary with hydration and protein intake, clinicians often interpret it together with creatinine to assess kidney function, using the ratio to help distinguish prerenal from kidney-related problems. The correct choice reflects this commonly used mid-range adult interval, which is why it’s the best answer. Keep in mind that exact numbers can differ slightly by lab, but the concept of a middle-range normal value for adults remains the same.

BUN measures the amount of nitrogen waste (urea) in the blood, a byproduct of protein metabolism that is filtered by the kidneys. In healthy adults, the reference values fall within a mid-range span used by most laboratories. Values within this mid-range are considered normal, while higher numbers can indicate dehydration, high protein intake, or reduced kidney function, and lower numbers can be seen with liver problems, malnutrition, or overhydration. Because BUN can vary with hydration and protein intake, clinicians often interpret it together with creatinine to assess kidney function, using the ratio to help distinguish prerenal from kidney-related problems. The correct choice reflects this commonly used mid-range adult interval, which is why it’s the best answer. Keep in mind that exact numbers can differ slightly by lab, but the concept of a middle-range normal value for adults remains the same.