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Metformin Stop eGFR Below 30 BNF — ESENeph MCQ

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EasyDiabetic Kidney DiseaseMetformin Stop eGFR Below 30 BNFESENeph

A 60-year-old man with CKD G4 (eGFR 18 mL/min/1.73m2) and type 2 diabetes has a creatinine of 310 umol/L. He takes metformin 1 g BD. His eGFR has been stable for 12 months. According to BNF and NICE guidance, what should happen to his metformin?

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Correct answer: A — Stop metformin — it is contraindicated below eGFR 30 mL/min/1.73m2

BNF and NICE guidance recommend reviewing metformin dose at eGFR 30-45 mL/min/1.73m2 (with dose reduction to maximum 1 g daily) and STOPPING metformin when eGFR falls below 30 mL/min/1.73m2 due to the risk of lactic acidosis from impaired renal clearance. At eGFR 18, metformin should be discontinued. The risk of metformin-associated lactic acidosis (MALA) increases significantly below eGFR 30 because metformin accumulates (renal clearance is the primary elimination route). Alternative glucose-lowering agents in CKD G4-5 include insulin (dose reduction needed), DPP-4 inhibitors (some dose-adjusted), and GLP-1 RAs (some usable to low eGFR). SGLT2 inhibitors can be continued for CKD benefit but have minimal glucose-lowering at this eGFR.

Reference: BNF 2024 – Metformin; NICE 2021 – NG203 CKD; KDIGO 2024 – CKD