The management of diabetes aims to control blood glucose concentrations and lower cardiovascular risk, thus limiting macrovascular and microvascular complications. Despite concerns about using thiazolidinediones in people with heart failure, these drugs remain at the centre of most prescribing algorithms for type 2 diabetes, including those recently published by the National Institute for Health and Clinical Excellence.1 In the linked cohort study (doi:10.1136/bmj.b2942), Juurlink and colleagues compare the risk of acute myocardial infarction, heart failure, and death in patients with type 2 diabetes treated with rosiglitazone and pioglitazone.2 Long term trials show that thiazolidinediones increase insulin sensitivity, lower glycated haemoglobin, and delay the progression of disease as measured by treatment failure with monotherapy.3 Both rosiglitazone and pioglitazone (the only thiazolidinediones currently on the market) have favourable effects on the cardiovascular risk profile over and above those achieved through glycaemic control alone.4 In addition, thiazolidinediones may have a place in the treatment of non-alcoholic steatohepatitis,5 and they may prevent progression from the metabolic syndrome to diabetes.6 However, various studies …