The prevalence of diabetes mellitus in the inpatient population is three times greater than in the general population. A significant proportion of inpatient expenditure in the UK is spent on the care of patients with diabetes. Despite this, patients with diabetes stay longer in hospital than patients without diabetes, and have increased mortality and morbidity. The emerging evidence is in favour of good glycaemic control, which requires control of hyperglycaemia and avoidance of hypoglycaemia. Although insulin is the preferred therapy in the inpatient setting, there remain serious concerns about its safe use.