Type 1 diabetes may appear at any age. The onset may be insidious and even asymptomatic for a long time. The prediabetic stage is characterized by genetic susceptibility, the presence of autoantibodies in serum, and gradual impairment of the β-cell function. HLA-DQ-encoded heterodimers are strongly associated with increased risk/protection. Additional diabetogenic genes are present in other chromosomes, different from HLA region genes. Screening of prediabetes is usually restricted to first-degree relatives of type 1 diabetic subjects. Islet cell antibody (ICA)-positive gestational diabetic women form a subset of patients with increased risk of developing type 1 diabetes shortly after pregnancy. Optimization of metabolic control is the key strategy for preventing late diabetic complications. Diabetic education, intensive insulin therapy and regular screening for early detection are critical in achieving this goal. Individual monitoring of subjects at high risk for developing hypoglycaemias, and development of more adequate short- and long-acting insulin analogues represent important measures to avoid hypoglycaemia and associated risks. Effective delivery of care for type 1 diabetic subjects requires the operation of a continuous quality assessment programme.