Most cases of lactic acidosis in patients taking metformin have been associated with shock or other tissue hypoxia. Elevated lactate in these patients may not be related to metformin. This is supported by the fact that lactic acidosis occurs as frequently in metformin users as users of other anti-diabetes medications (8). Also, metformin levels do not correlate with lactate levels or mortality suggesting that the underlying disease is more likely the cause of the acidosis than metformin (9). However this theoretical concern for an exceedingly rare complication has excluded metformin from use in hospitalized patients.