A 54-year-old man with type 2 diabetes on metformin 1 g twice daily has an eGFR of 32 mL/min/1.73 m². His HbA1c is 8.2%. Which statement about metformin use in this patient is most accurate per current ADA/KDIGO 2024 guidance?
- A Metformin must be stopped immediately because eGFR < 45 mL/min/1.73 m²
- B Metformin can be continued at a reduced dose with eGFR monitoring every 3 months; stop if eGFR falls below 30 ✓
- C Metformin is safe to continue at full dose as long as serum creatinine is below 1.5 mg/dL
- D Metformin should be replaced by sulfonylurea as the preferred agent at this eGFR level
Correct answer: B. Metformin can be continued at a reduced dose with eGFR monitoring every 3 months; stop if eGFR falls below 30
Explanation
Current ADA 2024 guidelines permit continued metformin use at reduced dose when eGFR is 30–45 mL/min/1.73 m², with monitoring every 3 months; it must be discontinued when eGFR falls below 30. The earlier threshold of stopping at eGFR < 45 was overly conservative and has been revised. Sulfonylureas carry hypoglycaemia risk with renal impairment and are not the preferred substitution.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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