Lactic acidosis is a rare but serious metabolic complication that can occur due to metformin HCl accumulation. The reported incidence of lactic acidosis during metformin HCl treatment is <0.1 case/1000 patient-years and the mortality risk is even lower.
Lactic acidosis is a medical emergency that must be treated in a hospital setting. In a patient with lactic acidosis, metformin HCl should be discontinued immediately and general supportive measures promptly instituted.