One of the most dreaded complications associated with metformin treatment is lactic acidosis, and this may serve to decrease the inclination of prescribers to initiate this useful drug for people with type II diabetes. A recently published study compared the association of acidosis in patients with type II diabetes who were prescribed metformin with those prescribed other antihyperglycaemic medications,  or no medications. Acidosis cases were stratified by exposure group and risk factors for lactic acidosis (chronic obstructive pulmonary disease, hepatic dysfunction, alcohol abuse, heart failure, renal insufficiency, age of 80 years or older, and a history of acidosis). An important .imitation was that the degree of renal insufficiency was not described. 24,936 people were treated with metformin only, 15,059  got other antihyperglycaemic medication and 92,785 (70% of the cohort) received no hypoglcaemic medication group. Acidosis was observed in 1.45 per 10,000 patient months (0.78 metformin, 1.59 other antihyperglycaemic medication, 1.51 no medication). There was no significant difference in risk of acidosis between exposure groups, irrespective of risk factors for lactic acidosis. The risk of acidosis was similar with metformin only compared with those prescribed other antihyperglycaemic medications or no medication at all. The authors advocate further studies to understand the impact of risk factor severity on risk of lactic acidosis.