What is the normal range for blood urea nitrogen (BUN) in mg/dL?

What is the normal range for blood urea nitrogen (BUN) in mg/dL?

• A. 5-15
• B. 8-25
• C. 20-40
• D. 25-50

Answer: (B)

Normal blood urea nitrogen (BUN) shows that the kidneys are clearing waste from protein metabolism effectively. Urea is formed in the liver and removed by the kidneys, so the typical reference range used in NBRC materials is about 8 to 25 mg/dL. Values lower than this are generally not considered normal for BUN in this testing context, while higher values—such as 20–40 or 25–50 mg/dL—suggest impaired renal function, dehydration, or increased protein turnover. Since BUN can be influenced by hydration and protein intake, it’s best interpreted alongside creatinine and the overall clinical picture, but 8–25 mg/dL is the standard normal range.

Normal blood urea nitrogen (BUN) shows that the kidneys are clearing waste from protein metabolism effectively. Urea is formed in the liver and removed by the kidneys, so the typical reference range used in NBRC materials is about 8 to 25 mg/dL. Values lower than this are generally not considered normal for BUN in this testing context, while higher values—such as 20–40 or 25–50 mg/dL—suggest impaired renal function, dehydration, or increased protein turnover. Since BUN can be influenced by hydration and protein intake, it’s best interpreted alongside creatinine and the overall clinical picture, but 8–25 mg/dL is the standard normal range.