RESUMEN
Metformin is widely prescribed for patients with type 2 diabetes mellitus (DM). Its use for patients with type 1 has been considered a contraindication because of possible adverse effects such as lactic acidosis. However, metformin has been recently used with insulin therapy to reduce insulin-dose requirements in Type 1 DM.<br>An 81-year-old Japanese woman with type 1 DM was treated with insulin and metformin. She was admitted to our hospital due to altered mental state and hypotensive shock via a referral from her primary care physician. The patient had severe lactic acidosis and acute kidney injury with hyperkalemia with the suspected cause being the use of metformin. She was treated successfully with hemodialysis (HD).<br>Although the independent predictive factor of mortality due to metformin-associated lactic acidosis is a prothrombin time (PT) activity of less than 50% in 24 hours, we recommend that HD should be performed for a patient with severe lactic acidosis even if the initial PT activity is normal.