The endothelium is the lining of the blood vessels that helps prevent damage to the vessels. The endothelium does not function as well as it should in adolescents with type 1 diabetes. This causes future diabetes complications. Adolescents with diabetes also have abnormalities of the cells that repair the endothelium. These abnormalities may be due to damage caused by intermittent hyperglycemia. This studied is designed to study whether low dose, combined Vitamin C and E supplementation improves endothelial function and repair in adolescents with type 1 diabetes.