Extreme lactic acidosis type B associated with metformin treatment

The elimination of metformin is exclusively through the kidneys and elevated plasma concentrations can cause lactic acidosis. We report a case of severe lactic acidosis (pH 6.60) occuring with ostensibly normal therapeutic doses of metformin in the setting of acute renal failure. Continuous veno-venous haemodiafiltration decreased plasma metformin concentrations from 266 lmol/L at presentation to 68 lmol/L, 21 h later. The patient improved rapidly.