A BUN-to-creatinine ratio less than 10:1 is typically seen in which scenarios?

• A. Dialysis, liver disease, low protein, starvation
• B. Pre-renal Azotemia
• C. Acute Kidney Injury
• D. High Protein Intake

Answer: (A)

A low BUN-to-creatinine ratio means that urea production is reduced or urea is being cleared more quickly than creatinine. Urea is made in the liver from ammonia, using dietary protein, so when liver function is impaired or protein intake is very low, BUN falls relative to creatinine, dropping the ratio. Starvation or malnutrition also reduces substrate for urea synthesis, producing the same effect. In patients undergoing dialysis, the procedure itself clears BUN, which can further lower the ratio compared with creatinine. That combination of reduced production or increased clearance explains why the ratio can fall below 10:1 in these scenarios.

In contrast, pre-renal azotemia raises the ratio because BUN reabsorption increases with decreased kidney perfusion, leading to a higher BUN relative to creatinine. Acute kidney injury from intrinsic kidney damage and high protein intake don’t characteristically produce a low ratio; they tend to show normal or higher ratios depending on the exact situation.