Diabetes and heart failure are closely related: patients with diabetes have an increased risk of developing heart failure and those with heart failure are at higher risk of developing diabetes. Furthermore, antidiabetic medications increase the risk of mortality and hospitalisation for heart failure in patients with and without pre-existing heart failure. When the two diseases are considered individually, heart failure has a much poorer prognosis than diabetes mellitus; therefore heart failure has to be a priority for treatment in patients presenting with the two conditions, and the diabetic patient with heart failure should be managed by the heart failure team. No specific randomised clinical trials have been conducted to test the effect of cardiovascular drugs in diabetic patients with heart failure, but a wealth of evidence suggests that all interventions effective at improving prognosis in patients with heart failure are equally beneficial in patients with and without diabetes. The negative effect of glucose-lowering agents in patients with heart failure or at increased risk of heart failure has become evident after the withdrawal of rosiglitazone, a thiazolidinedione, from the EU market due to evidence of increased risk of cardiovascular events and hospitalisations for heart failure. An important issue that remains unresolved is the optimal target level of glycated haemoglobin, as recent studies have demonstrated significant reductions in total mortality, morbidity and risk of heart failure despite achieving HbA1c levels similar to those observed in the UKPDS study conducted some decades ago. Meta-analyses showed that intensive glucose lowering is not associated with any significant reduction in cardiovascular risk but conversely results in a significant increase in heart failure risk. Different medications have different risk: benefit ratios in diabetic patients with heart failure; therefore, the heart failure team must judge the required intensity of glycaemic control, the type and dose of glucose lowering agents and any change in glucose-lowering therapy, according to the clinical conditions present.