1. Temporary decline in islet function Mechanism: Including some emergency states, surgery, etc., due to the toxic effect of severe hyperglycemia, and the islet secretion function is in a dormant state. Generally, after receiving short-term insulin therapy and relieving glucotoxicity, islet function is expected to be restored, and oral hypoglycemic drugs that originally failed may also regain their efficacy. Treatment: Insulin therapy is recommended at this time, never have concerns about insulin dependence, and use insulin when it is time to use it. 2. Absolute decline of pancreatic islet function Mechanism: With the prolongation of diabetes onset, the general pancreatic islet function decreases at a rate of 5% to 10% per year until it slowly fails, which may cause a decrease in the effect of oral hypoglycemic drugs and even secondary failure. Treatment: In case of secondary failure, blood glucose may still be poorly controlled even if the dose or type of oral medication is continuously increased. At this time, oral medication can no longer control blood sugar well, and it is necessary to consider switching to insulin, or combining insulin treatment with oral medication. 3. Poor control of diet and exercise Mechanism: Poor control of diet and lack of exercise will lead to postprandial blood sugar fluctuation and weight gain. At the same time, it will increase insulin resistance, make the body insensitive to insulin and make the effect of glucose-lowering drugs decrease. Treatment: Dietary control and moderate exercise are essential measures in the treatment of diabetes.