Diabetes mellitus is a common condition in children, characterised by chronic hyperglycaemia resulting from an absolute insulin deficiency. It can present in various ways, and hospital admission may result from complications related to previously diagnosed diabetes, or from a new diagnosis. To raise awareness of the condition, Diabetes UK has launched the 4Ts campaign, which highlights the four most common symptoms of diabetes. This article discusses the different clinical presentations, diagnosis and management of children with diabetes, and includes two case studies to illustrate some of the challenges faced by emergency department nurses.