ITS NOT ALWAYS DKA. A. Tabas 1 , G. Tabas 1 ; 1 University of Pittsburgh Medical Center Shadyside, Pittsburgh, PA LEARNING OBJECTIVES: 1.Recognize lactic acidosis as a complication of metformin use. 2.Differentiate between diabetic ketoacidosis and metformin induced lactic acidosis. CASE INFORMATION: A 22 year old black female was admitted with three days history of nausea, vomiting, headache and abdominal pain, preceded by two days of rhinorrhea, and diarrhea. She was diagnosed with insulin requiring diabetes three years ago. There was no history of pre-existing renal insufficiency, chronic pulmonary disease or heart disease. Her medication was changed from insulin to metformin 500 mg bid a week prior to hospitalization. Her physical exam revealed tachycardia, and tachypnea. Pulse oximetry revealed 100% saturation on room air. The rest of the exam was unremarkable. Laboratory data were significant for ABG on room air - . Sodium-139 meq/L, Potassium-4.3 meq/L, Chloride-106 meq/L, CO 2 -7 meq/L, BUN-5 mg/dl, Creatinine-0.8 mg/dl, Glucose-276mg/dl, serum acetone-positive. The anion gap was 26. CBC & differential, and chest x-ray were within normal limits. Lactate and metformin levels were not checked. The patient was treated with normal saline, insulin drip, sodium bicarbonate and metformin was held. The metabolic acidosis resolved and the patient was discharged on long acting insulin. DISCUSSION: We do not know whether our patient had atypical diabetic ketoacidosis or metformin induced lactic acidosis. The presenting serum glucose in patients with diabetic ketoacidosis is usually between 450 mg/dl and 750 mg/dl. This patient's initial serum glucose of 276 mg/dl is somewhat uncommon for diabetic ketoacidosis, and suggests that other causes of high anion gap acidosis must be considered. The incidence of lactic acidosis is about 9 per 100,000 person-years in patients taking metformin. It usually occurs in patients who have preexisting cardiac disease, congestive heart failure, chronic pulmonary disease with hypoxia, sepsis or old age. Metformin induced lactic acidosis in patients such as ours, with no pre-existing risk factors, is rare but has been reported in literature. The mechanism is unknown. In patients taking metformin, presenting with ketoacidosis, metformin induced lactic acidosis should be considered. Assessing risk factors, appropriate laboratory workup (arterial lactate level, metformin level), withdrawing metformin and supportive care are key components of management.