Normal BUN-to-creatinine ratio is typically within which range?

• A. 5-7:1
• B. 10-20:1
• C. 25-30:1
• D. 40-50:1

Answer: (B)

The essential idea is how the BUN-to-creatinine ratio reflects kidney function and hydration, using two markers that respond differently to body conditions. BUN depends on protein intake, liver function, and especially hydration, so it can rise with dehydration or high protein intake. Creatinine, produced from muscle and filtered by the kidneys, stays relatively constant in the short term. Because these factors shift independently, a healthy person’s ratio stays in a narrow window. The normal range is about 10:1 to 20:1. When the ratio exceeds roughly 20:1, it points toward a prerenal state like dehydration where BUN climbs more than creatinine. If the ratio is significantly lower, it can indicate intrinsic kidney issues or conditions that lower BUN production. So the typical normal ratio to memorize is 10:1 to 20:1.