Metformin, an antihyperglycemic, is widely used in the treatment of type 2 diabetes mellitus (DM). A rare, but important complication associated with this drug is the development of lactic acidosis: Overall mortality of lactic acidosis is approximately 50%. Certain subsets of patients taking metformin are at greater risk of developing lactic acidosis. This report discusses the development of metformin-associated lactic acidosis in four older adults admitted to an institution during a 2-month period, treatments, and outcomes. We recommend an aggressive treatment strategy of hemodialysis followed by peritoneal dialysis, continuous bicarbonate infusion, and tight glucose control. We review the cautions and contraindications of metformin use for the treatment of type 2 DM and report an educational plan for residents and staff instituted to improve drug complication awareness and reduce mortality.