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Metformin gastrointestinal effects — USMLE Step 3 MCQ

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ModerateAmbulatory Medicine / Primary CareMetformin gastrointestinal effectsUSMLE Step 3

A 51-year-old man started metformin 2 weeks ago for newly diagnosed type 2 diabetes. He reports bloating and loose stools after each dose. He has no fever, blood in stool, abdominal tenderness, or dehydration. Creatinine is normal. Which of the following is the most likely explanation for this patient's findings?

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Correct answer: A — Dose-related gastrointestinal adverse effect of metformin

Metformin commonly causes dose-related gastrointestinal symptoms early in treatment; dose titration or extended-release formulation can help.

Reference: American Diabetes Association Standards of Care in Diabetes—2026: https://professional.diabetes.org/standards-of-care