A 15-year-old girl developed lactic acidosis and hypoglycaemia after ingesting an overdose of metformin in a suicide attempt [time to reaction onset not stated].The girl developed abdominal pain and was admitted in a casualty department due to metformin poisoning after she ingested 40 tablets of metformin 1000mg. Gastric lavage was performed, and she received charcoal. Glucose was administered after a blood sugar level of 28 mg/dL was measured. She was moved to an ICU when she developed fluctuating consciousness, agitation and pronounced Kussmaul breathing. Tests showed the following results: blood sugar 35 mg/dL, pH 6.99, HCO3 6.3 mmol/L, pCO2 27.3mm Hg, base excess -22.7 mmol/L, lactate 134 mg/dL, haemoglobin 12.5 g/dL, leucocyte 17 000/mm 3 , platelet 389 000/mm 3 , urea 21 mg/dL, creatinine 1.97 mg/dL, sodium 123 mEq/L and potassium 3.1 mEq/L.The girl received bicarbonate treatment, but her respiratory distress increased and she was intubated. She developed hypotension and dopamine was started. She underwent two haemodiafiltration sessions and was extubated. Tests performed on the fourth day of admission revealed the following: pH 7.44, HCO3 22 mmol/L, pCO2 45.3mm Hg, base excess -1.5 mmol/L, lactate 7 mg/dL, urea 20 mg/dL, creatinine 0.53, sodium 135 mEq/L and potassium 3.7 mEq/L. She was discharged from the ICU.Author comment: A known toxic effect resulting from the acute and chronic use of biguanides is lactic acidosis. In addition, hypoglycaemia can develop with an overdose of metformin. Eren E, et al. Metformin intoxication in an adolescent. Turk Pediatri Arsivi 47: 313-314, No. 4, 2012. Available from: URL: http://dx.doi.org/10.4274/tpa.1004 [Turkish; summarised from a translation] -Turkey