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Metformin Contrast Timing CKD — ESENeph MCQ

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EasyAcute Kidney InjuryMetformin Contrast Timing CKDESENeph

A 62-year-old woman with CKD G3b and type 2 diabetes is on Metformin 500 mg BD. Her eGFR has been stable at 35 for 2 years. She develops an acute illness requiring a CT with iodinated contrast. What is the Metformin management around contrast?

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Correct answer: B — Withhold Metformin from the time of contrast administration and for 48 hours after; check renal function at 48 hours before restarting – this prevents lactic acidosis if contrast-induced AKI occurs

Metformin itself is not nephrotoxic, but if contrast-induced AKI occurs, Metformin accumulates and can cause life-threatening lactic acidosis. ESUR 2018 and NICE recommend withholding Metformin at the time of contrast in patients with eGFR <30 (some guidelines use <45) and checking renal function at 48 hours. If creatinine is stable, Metformin can be restarted. In patients with eGFR >60, Metformin can usually be continued. The key intervention for preventing contrast AKI itself is IV hydration, not Metformin management.

Reference: ESUR 2018 – Contrast Guidelines; NICE AKI 2019; BNF – Metformin