Which laboratory finding would indicate vancomycin-induced nephrotoxicity?

• A. Increased serum creatinine level
• B. Decreased BUN level
• C. Increased blood pressure
• D. Intermittent flank pain

Answer: (A)

Vancomycin can cause kidney injury, and the main lab signal is a rise in serum creatinine, which reflects a drop in glomerular filtration rate. Creatinine is produced at a constant rate and cleared by the kidneys; when filtration is impaired, its level in the blood increases, signaling nephrotoxicity from vancomycin. BUN can also rise with kidney injury but is influenced by hydration, protein intake, and other factors, making it a less specific marker. Increased blood pressure is not a direct lab marker of nephrotoxicity, and intermittent flank pain isn’t a laboratory finding related to kidney injury. So the increase in serum creatinine is the best indicator.