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Metformin in renal impairment — GPhC CRA MCQ

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HardEndocrine TherapeuticsMetformin in renal impairmentGPhC CRA

A 68-year-old man with type 2 diabetes takes metformin 1 g twice daily. He presents a discharge prescription after treatment for dehydration; his eGFR is now 24 mL/min/1.73 m2 and lactate was mildly raised in hospital. What is the most appropriate action?

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Correct answer: A — Query continuation of metformin because renal function is too low

Metformin accumulation is a concern in significant renal impairment and acute illness, with lactic acidosis as a rare but serious risk. An eGFR of 24 mL/min/1.73 m2 is below the usual threshold for use, so continuation should be queried before supply. Changing formulation would not address the safety issue.

Reference: BNF; NICE CKS