Type 1 diabetes Mellitus happens when the part of the pancreas that makes insulin is destroyed by that person’s own immune system. When the pancreas does not make insulin, glucose – sugar – in the blood cannot get into the parts of the body that need sugar to live. In order to live, a person with type 1 diabetes must take insulin for the rest of their life. They need to check their blood sugar level on a regular basis, often, many times each day.