China Diabetes Type 1 Study (CD1S) by China Alliance for Type 1 Diabetes

Inclusion Criteria: * 1\. Patients with type 1 diabetes mellitus of any duration; meeting criteria (1) or any of (2) or any of (3) 1. Clinical diagnosis of type 1 diabetes by a specialist 2. Age at onset \< 15 years; no overweight or obesity at onset; previous diabetic ketoacidosis; highest random C-peptide \< 200 pmol/L 3. Initiation and continuation of insulin therapy (except pancreatic or islet transplantation) after diagnosis; positive islet autoantibodies Or 2. Children and adolescents with diabetes mellitus at age of onset \<= 20 years, regardless of type and duration of disease. Exclusion Criteria: * For enrolment of patients with T1D, exclusion was made if any of the following criteria were met (not applicable to those with onset under 20 years of age) * No insulin dependence for at least 6 months after diagnosis of diabetes mellitus. * No DKA for 1 month off insulin for those with a history of diabetes \> 1 year. ③ C-peptide \> 800 pmol/L at any time point.