The natural course of type 2 diabetes reveals that insulin resistance exists in the early stage of the disease, and clinical hyperglycemia occurs when the quality and quantity of insulin secretion are insufficient to maintain normal glucose metabolism and overcome insulin resistance as the function of pancreatic β-cells decreases, and as the disease progresses, insufficient insulin secretion becomes the main conflict. The UKPDS study showed that at the initial diagnosis of type 2 diabetes, β-cell function is about 50% of normal, and as the disease progresses, β-cell function declines at a progressive rate of 4.5% per year. In other words, in type 2 diabetes, there is not only insulin resistance, but also insufficient insulin action and progressive decline of islet function. Therefore, for patients with type 2 diabetes who need insulin therapy in clinical practice, timely application of insulin is beneficial to the recovery of islet function and blood glucose control.