Metformin

Biguanide

Drug Class: Biguanide
Mechanism of Action (MOA): ↓ hepatic gluconeogenesis and ↑ peripheral insulin sensitivity (does not stimulate insulin secretion).
Black Box Warning: Lactic acidosis — risk rises with renal or hepatic impairment, age ≥65, iodinated contrast, hypoxic states, alcohol.
Clinical Notes: First-line for type 2 DM; weight-neutral, no hypoglycemia as monotherapy. GI upset, lowers vitamin B12. Hold for iodinated contrast.
Source: FDA label

Sources

Reviewed September 2026

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