Diabetes mellitus is a disease that prevents the body’s proper use or production of insulin—the hormone responsible for converting blood sugar (glucose) into energy. Without insulin, too much glucose circulates in the blood, causing damage. Whether you have type 1 diabetes or type 2 diabetes, the potential complications are the same: gastroparesis (slower emptying of stomach contents) diabetic ketoacidosis (DKA) and coma, diabetic neuropathy, kidney damage, diabetic retinopathy (which may result in blindness), and other problems.