Type 1 diabetes requires long-term insulin injections once diagnosed. Type 1 diabetes mellitus is divided into type 1A and type 1B. Type 1A diabetes mellitus, also known as immune-mediated diabetes mellitus, is positive for islet autoantibodies; type 1B diabetes mellitus, also known as idiopathic diabetes mellitus, is usually of rapid onset, with marked pancreatic β-cell failure, and can easily lead to diabetic ketoacidosis, but is negative for islet autoantibodies. Type 1 diabetes is characterized by an absolute deficiency in insulin secretion, and once diagnosed, insulin therapy should be initiated and lifelong replacement therapy is required. The insulin regimen needs to be individualized due to differences in the function of the patient’s residual pancreatic β-cells. Patients with type 1 diabetes should be treated under medical supervision.