How will lack of insulin harm people with diabetes?

No sugar in cells.: Insulin is the hormone secreted by the pancreas to get glucose inside the cells and out of the bloodstream. In diabetes type i, the beta-islet cell of the pancreas are destroyed, and no Insulin is secreted. This means glucose builds up in the blood and the cells don't get it, therefore they starve, and death results if untreated. So treatment is to give them insulin.