Lactic acidosis is a known adverse risk of metformin treatment. Here we háve outlined a čase in which lac¬tic acidosis developed during treatment of a diabetic patient in whom there were no contraindications to metformin treatment. Lactic acidosis was caused by acute renal failure leading to metformin accumulation. The acute renal failure was caused by a combination of dehydration due to a low intake of fluids when disabled because of a fractured ankle, concomitant diuretic treatment of arterial hypertension and angioten-sin-converting enzyme inhibitor treatment. The patient was successfully treated by a combination of hae-modialysis and infusion therapy. We recommend that all patients on metformin should consider temporari-ly discontinuing treatment in the event of severe illness, including dehydration.

        Key words: lactic acidosis, metformin, renal failure, type 2 diabetes