Insulin of choice for the treatment of diabetes mellitus is:

(Ref: Katzung 14th ed. P 753)Regular insulin is a short-acting, soluble crystalline zinc insulinHypoglycemic effect appears within 30 minutes after subcutaneous injection, peaks at about 2 hours, and lasts for 5-7 hours.For very insulin-resistant subjects who would otherwise require large volumes of insulin solution, a U500 preparation of human regular insulin is available both in a vial form and a disposable penIV infusion: used in treatment of diabetic ketoacidosis