The causes of type 1 diabetes are not fully known. In most cases, the body’s immune system attacks and destroys the part of the pancreas that produces insulin. This occurs over a period of time. so early on in type 1 diabetes, people may not have any symptoms. It is only when enough of the insulin producing cells are affected and insulin producing cells are affected and insulin levels are low that blood sugar rises and symptoms of diabetes start to occur. Because type 1 is an autoimmune disease, people with other autoimmune, conditions, such as Hashimoto disease or primary adrenal insufficiency (also known as Addison's Disease), are more likely to develop type 1 diabetes. Overall, cases of type 1 diabetes seem to be increasing.