Contributor: Don Stader, MD Educational Pearls: The common causes of anion gap metabolic acidosis include (MUDPILES) Metformin, Methanol  Uremia  DKA Paraldehyde  INH/Iron  Lactate Ethylene Glycol  Salicylate  Metformin is a very common drug used to treat type 2 diabetes, however in the right setting, it can cause a profound lactic acidosis. There is a very high mortality rate.  Treatment of metformin toxicity includes fluids, bicarb, and dialysis  Most commonly, metformin toxicity is in the setting of kidney injury or overdose.  Always consider acidosis in those with tachypnea!  References Re-evaluation of a biguanide, metformin: mechanism of action and tolerability. Sirtori CR, Pasik C Pharmacol Res. 1994;30(3):187.  Bicarbonate haemodialysis as a treatment of metformin overdose.Heaney D, Majid A, Junor B. Nephrol Dial Transplant. 1997;12(5):1046.  Extracorporeal Treatment for Metformin Poisoning: Systematic Review and Recommendations From the Extracorporeal Treatments in Poisoning Workgroup.Calello DP, Liu KD, Wiegand TJ, Roberts DM, Lavergne V, Gosselin S, Hoffman RS, Nolin TD, Ghannoum M, Extracorporeal Treatments in Poisoning Workgroup Crit Care Med. 2015;43(8):1716.  Metformin accumulation: lactic acidosis and high plasmatic metformin levels in a retrospective case series of 66 patients on chronic therapy.Vecchio S, Giampreti A, Petrolini VM, Lonati D, Protti A, Papa P, Rognoni C, Valli A, Rocchi L, Rolandi L, Manzo L, Locatelli CA Clin Toxicol (Phila). 2014;52(2):129.    Summarized by Will Dewispelaere, MS4 | Edited by Erik Verzemnieks, MD