Since the introduction of insulin in 1921, it has been playing an irreplaceable role in treating diabetes and saving the lives of patients. However, although various insulins and insulin analogues have been successfully developed and used in clinical practice, the only effective and long-term adherence route is subcutaneous injection, and patients who need insulin therapy inevitably endure the pain of needling again and again. After the pain, people fantasize that they can have oral insulin. Many unscrupulous people and unscrupulous businessmen seize this psychology of people and advocate the benefits of oral insulin, produce the so-called oral insulin and make profits from it, making many patients suffer huge economic losses in addition to uncontrollable disease. Insulin is a peptide composed of 51 amino acids, which is a protein, and will be decomposed by pepsin and lose its effect after oral administration, just like meat. Although some people abroad are studying to wrap a film around insulin or add some substances to make insulin not be decomposed by pepsin after oral administration, they are not successful, and even if they are successful, it is not possible to popularize it because it is expensive. Therefore, only subcutaneous injection is the most effective way of insulin administration, and oral administration is a fraud.