In this review, our primary end points are to present the existing data about the results of bariatric surgery on T1DM patients concerning weight loss, reduction in insulin requirements, changes in glycosylated hemoglobin (HbA1c) and metabolic comorbidities, along with the main complications and risks, especially diabetic ketoacidosis (DKA) and hypoglycemia. This evidence concerns the gene INS and diabetic ketoacidosis.