Insulin has been in use for the treatment of patients with diabetes mellitus for over 75 years. However, despite the known benefits of tight glycaemic control, multiple insulin injections have still not gained widespread clinical acceptance. Although there have been attempts to find effective non-invasive routes for insulin delivery, none of the novel non-invasive approaches have become part of established practice. In fact, until recently it was believed that as a result of limitations, non-invasive insulin was not a clinically realistic option. However, preliminary studies have indicated that inhaled insulin may emerge as an effective, well-tolerated, non-invasive alternative to subcutaneous regular insulin. The pharmacokinetics of inhaled insulin show a more physiological profile compared to conventional insulin; however, further studies to confirm long-term pulmonary safety and efficacy are needed.