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Metformin-associated vitamin B12 deficiency — SCE Endocrinology MCQ

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ModerateDiabetesMetformin-associated vitamin B12 deficiencySCE Endocrinology

A 69-year-old man with type 2 diabetes takes metformin 1 g twice daily and insulin glargine. He reports numb feet and poor balance; HbA1c is 51 mmol/mol. Vibration sense is reduced, ankle reflexes are absent and mean corpuscular volume is 106 fL. What is the most appropriate next investigation?

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Correct answer: D — Serum vitamin B12 concentration

Metformin is associated with vitamin B12 deficiency, which can mimic or worsen diabetic neuropathy and causes macrocytosis. Nerve biopsy is not the initial investigation in a typical metabolic neuropathy presentation. The pearl is that not every neuropathy in diabetes is diabetic neuropathy.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/diabetes-and-other-endocrinal-nutritional-and-metabolic-conditions