Which action is most appropriate for a 68-year-old man with type 2 diabetes on ramipril with eGFR 28 and potassium 5.2 mmol/L?

• A. Continue metformin and monitor
• B. Reduce metformin dose
• C. Stop metformin and refer to prescriber
• D. Stop ramipril

Answer: (C)

The main idea is safety of metformin in kidney impairment. Metformin clearance depends largely on kidney function, and when the eGFR falls below 30 mL/min/1.73 m2, the risk of lactic acidosis increases, so metformin is contraindicated. An eGFR of 28 means metformin should be stopped, and the patient’s prescriber should be consulted to choose an alternative glucose-lowering strategy and adjust the regimen as kidney function and potassium are reassessed.

Stopping metformin and referring to the prescriber is the best choice because continuing or just reducing the dose would still be unsafe with eGFR this low. Stopping ramipril isn’t required solely due to this level of kidney function and mildly elevated potassium (5.2 mmol/L); ramipril may be continued with monitoring and management of potassium, unless there are other compelling reasons to stop. The key takeaway is recognizing when metformin becomes unsafe because of significantly reduced renal function and taking action to involve the prescriber for safer alternatives.