Type I diabetes usually occurs in people who are below the age 20 and that is why it is also called as juvenile diabetes. In this type, the body becomes partially or completely unable to produce insulin. Type I diabetes is an autoimmune disease. In this, your immune system attacks the pancreas from where the insulin is produced, thereby making the pancreas inefficient or unable to produce insulin. Type I diabetes cannot be prevented, it can only be controlled with healthy lifestyle changes.
Family or personal history. Your risk increases if you have prediabetes — a precursor to type 2 diabetes — or if a close family member, such as a parent or sibling, has type 2 diabetes. You're also at greater risk if you had gestational diabetes during a previous pregnancy, if you delivered a very large baby or if you had an unexplained stillbirth.