There isn’t just one cause for developing diabetes. Some doctors really don’t know why some people will develop the disease and another person who has the same daily routine will avoid the illness. Many people have diabetes because a family member has it as it can be hereditary. There are also some people who develop the disease simply because they don’t maintain a proper diet.
This is the most common cause of diabetes. It's often a primary reason why people develop Type 1 diabetes as this is the type that is seen in children and teenagers.
There are some variations of genes that can tell the body not to produce the proper levels of insulin. These genes are passed from parents to the children or from grandparents, uncles and aunts to other family members. A grandparent might have diabetes, the child might not have it, but the grandchild might have Type 1.