Type 1 diabetes mellitus is the most common chronic endocrine disease worldwide in children. It is characterised by autoimmune destruction of the β cells leading to insulin deficiency. This process occurs in genetically susceptible persons, is probably triggered by one or more environmental factors.The incidence of type 1 diabetes mellitus is rising, especially in young children (age <5 years). The signs and symptoms of disease in children usually develop quickly, over a period of a few weeks. Typical symptoms include polyuria, polydipsia and weight loss. In some patients diabetic ketoacidosis, a life-threatening metabolic state, can be an initial presentation of type 1 diabetes mellitus. Diabetes management is complex and challenging, particularly during childhood and adolescence. Insulin therapy is the mainstay in management of type 1 diabetes mellitus. There are many different insulin preparations and delivery systems available. Intensive insulin therapy compared with conventional therapy improves glycemic control and decreases long-term complications of diabetes. Other important issue in the management of children with type 1 diabetes mellitus include nutrition. The main therapeuthic goal is good glycemic control of a disease (glycated haemoglobin <7,5%) in order to prevent short and long term diabetic complications. The most common complications of type 1 diabetes mellitus in children include hypoglycemia, hyperglycemia and diabetic ketoacidosis.