Diabetes is a syndrome of disordered metabolism and inappropriate hyperglycemia resulting from a deficiency of insulin secretion or insulin resistance. Insulin, a pancreatic hormone, helps to lower the blood sugar levels. The structural features of insulin and insulin receptors are summarized. Diabetic patients use insulin in the form of injections, which involves lots of pain, and a need for non-invasive, alternative mode of insulin administration is desired. These challenges have lead to attempts in insulin therapy using oral, nasal, pulmonary, rectal, transdermal, buccal, gene therapy, islet cell transplantation and diabetes vaccine. Among all the approaches pulmonary administration has achieved some clinical significance. Future approaches that can be exploited for insulin therapy in Insulin Dependent Diabetes Mellitus [IDDM] have been summarized. Insulin inhalers or tablets for IDDM are interesting alternatives.