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MALA — RACP Adult Medicine MCQ

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HardEndocrinologyMALARACP Adult Medicine

A 60-year-old man with T2DM on metformin 2 g daily presents with severe lactic acidosis (pH 6.95, lactate 18 mmol/L). He developed AKI from dehydration (creatinine risen from 90 to 450 μmol/L). He is hypotensive and oliguric. Blood glucose is 8 mmol/L. Ketones are 0.8 mmol/L. What is the most likely diagnosis?

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Correct answer: B — Metformin-associated lactic acidosis

Severe lactic acidosis (type B) with AKI reducing metformin clearance causing accumulation is metformin-associated lactic acidosis (MALA). Metformin inhibits mitochondrial complex I, promoting anaerobic metabolism. MALA is rare but has ~50% mortality. Treatment: cease metformin, aggressive IV resuscitation, sodium bicarbonate for pH <7.0, and haemodialysis (removes metformin AND corrects acidosis). Metformin is dialysable. Prevention: withhold metformin when eGFR <30 or during acute illness with dehydration risk.

Reference: AMH – 2025 – Metformin; eTG Endocrine 2024