The importance of insulin in the management of diabetes mellitus cannot be over emphasized. Newer formulations and delivery devices have improved the efficacy, safety and tolerability of insulin. All available insulins and insulin analogues, however, are administered by subcutaneous insulin. The subcutaneous route of administration is associated with a certain level of discomfort, which is not acceptable to some patients. This has led researchers to explore other methods of insulin delivery. Inhaled insulin, nasal insulin and oral insulin are some of the novel insulins which have been studied. This review highlights recent advances and patents related to oral insulin. It covers the limitations of subcutaneous insulin, the physiological rationale of administering oral insulin, and the barriers to these formulations. The review is based on a literature search, done by all authors, using the key words “oral insulin”, from 1991 to 2010, using PubMed and Google Scholar. All four authors decided the relative importance of papers on various oral insulin formulations. Focus was kept on oral preparations which are still in active development, and stand a chance of reaching the commercial market. The review studies the methods of producing oral insulin such as encapsulation, protease inhibitor use, PEGylation, permeation enhancer use and liposomal administration. It highlights recent patents and studies for all these methods.