RESUMO
Type 2 diabetes, a world-wide epidemic, is a major concern of health systems around the world. The recommandation of its early management with metformin by the majority of guidelines has made metformin the object of multiple studies to demonstrate its benefits, but more importantly its side effects among whom the most serious is lactic acidosis. The latter is rare, but responsible for high mortality rates and is strongly associated with acute and chronic conditions for which diabetics are prone. These conditions reduce tissue perfusion and activate anaerobic metabolism producing lactate. Despite the beneficial effects of metformin and the debate about its causal role, we should remain vigilant about this serious complication by respecting its usage's contraindications, for the time being unchanged.