Epidemiology of type 1 diabetes and its complications. The prevalence of type 1 diabetes in adult is estimated at 0.3 to 0.5%, or 10% of all types of diabetes. In youth less than 15 years, in France, the incidence of type 1 diabetes is 18 per 100,000 over the period 2013-2015 (based on the National Health Data System), corresponding to an approximate prevalence of 1.3 per 1000. The incidence of diabetes in youth increases by 3 to 4% per year, an increase seen in France since 1988. With the intensification of treatment (resulting in HbA1c around 8% on average over the entire follow-up), after 30 years of progression of diabetes (in subjects aged 50 years on average), it was observed that the prevalence of severe retinopathy (requiring laser treatment) was nearly 15%, microalbuminuria 15%, macroproteinuria 4%, advanced renal failure less than 2%, clinical neuropathy 24%, and macrovascular complications around 5%., Competing Interests: I. Allix, C. Briet, P. Denis, A. Fagot Campagna, S. Fosse et C. Piffaretti déclarent n'avoir aucun lien d'intérêts. R. Coutant déclare des liens ponctuels (essais cliniques, conférences, colloques, prise en charge lors de congrès) avec Lilly et Novo Nordisk.