With the prolongation of type 2 diabetes, most patients need two or more oral hypoglycemic drugs to control their blood glucose in a more ideal range due to the aggravation of insulin resistance and pancreatic B-cell hypofunction. Since the glucose-lowering mechanisms of various oral hypoglycemic drugs are different, the reasonable combination of drugs can not only reduce the dose of single drugs, reduce the possible toxic side effects of drugs, but also different oral hypoglycemic drugs can complement each other’s strengths and weaknesses, which is more conducive to the control of blood sugar. The combined use of oral hypoglycemic drugs generally follows the following general principles. First, try to combine the use of drugs with different glucose-lowering mechanisms, and avoid the joint application of similar drugs with the same mechanism of action. Because the joint application of similar hypoglycemic drugs leads to a great increase in the possibility of toxic side effects, while the joint use of drugs with different hypoglycemic mechanisms can produce better hypoglycemic effects, and the occurrence of adverse drug reactions is greatly reduced due to the reduction of drug doses; secondly, the joint use of a single hypoglycemic drug should be used as early as possible when the glycemic control is poor, and do not wait until the maximum dose of a single drug is still ineffective before considering the joint use of drugs; thirdly, the type of joint use of drugs should not be used in combination. Thirdly, there should not be too many kinds of combined drugs, generally two drugs are combined, three drugs can be combined if necessary, and four or more drugs should be avoided as far as possible; finally, the combination of oral hypoglycemic drugs should take into account the drug economics, and avoid the combination of expensive hypoglycemic drugs. At present, the commonly used oral hypoglycemic drugs in clinical practice mainly include sulfonylurea hypoglycemic drugs, biguanide hypoglycemic drugs, mealtime glucose regulators, thiazolidinediones, α-glucosidase inhibitors and so on. The more commonly used combination of oral hypoglycemic drugs in clinical practice mainly includes the following. 1, sulfonylurea + biguanide The combination of sulfonylurea and biguanide hypoglycemic drugs is very common, obese people preferred biguanide drugs, non-obese people preferred sulfonylurea drugs, but when the single drug can not satisfactorily control blood sugar, you can consider the combination of the two, to reduce fasting blood sugar and postprandial blood sugar have good effect, and low cost. However, in the combination of both drugs, the risk of hypoglycemia will be increased, especially for elderly patients. In addition, since most of the two types of drugs are excreted by the kidneys, it will increase the burden on the kidneys, and the kidney function should be tested regularly, and the program should be adjusted in time when there is renal impairment. 2. Sulfonylurea + α-glucosidase inhibitor When sulfonylurea alone cannot effectively control postprandial blood sugar, the addition of α-glucosidase inhibitor should be considered to bring postprandial blood sugar under control. Since this drug can continuously inhibit postprandial hyperglycemia and reduce insulin requirement, the dose of sulfonylurea in combination can be reduced without increasing body weight. Although α-glycosidase inhibitor alone will not cause hypoglycemic reaction, it will increase the risk of hypoglycemia when combined with sulfonylureas, and if hypoglycemia occurs, glucose should be used to correct it. 3.Biguanide + α-glucosidase inhibitor The combination of these two types of drugs can produce significant synergistic effects, which can significantly reduce fasting and postprandial blood sugar in diabetic patients, and also have a certain effect on improving abnormal lipid metabolism and insulin resistance in patients, which is more suitable for obese diabetic patients. However, it should be noted that the combined application of the two types of drugs may increase nausea, abdominal discomfort and other gastrointestinal reactions. 4, sulfonylurea + thiazolidinediones For patients with poor glycemic control with sulfonylureas alone, especially those with hyperinsulinemia, thiazolidinediones can be added, and the combination of the two can reduce the occurrence of secondary failure of sulfonylureas, so that blood glucose can be satisfactorily controlled. In the combined use to pay attention to the possible occurrence of hypoglycemia, the dose of sulfonylureas should be reduced, in addition, if the patient has appeared islet failure, then add thiazolidinediones, often difficult to achieve the desired effect. 5, biguanides + thiazolidinediones Both can increase insulin sensitivity, for patients whose blood sugar is still poorly controlled with biguanides alone, especially patients with severe obesity with obvious insulin resistance and mild to moderate elevation of blood sugar is more desirable. Some studies have confirmed that the combination of the two has complementary effects in reducing hyperglycemia, and the combination of the two can reduce glycated hemoglobin by 0.7%-0.8% on average compared with single medication. 6, mealtime glucose regulator + biguanide mealtime glucose regulator can quickly stimulate insulin secretion, which is more conducive to postprandial blood sugar control and lower incidence of hypoglycemia. As mealtime glucose regulators are taken at mealtime and not at mealtime, they are more suitable for patients with irregular diet, such as drivers, and can avoid the occurrence of hypoglycemia. The combination of mealtime glucose regulator and biguanide has a synergistic effect without obvious adverse effects, which is conducive to the long-term blood sugar control of patients and further improves the quality of life, and has no obvious effect on body weight. 7. Other combination programs The above are the more common clinical combination programs of oral hypoglycemic drugs. In practice, other combination programs can be selected according to the condition, such as the combination of thiazolidinediones and α-glucosidase inhibitors, which is suitable for patients with insulin resistance and high postprandial glucose. In addition, when the combination of 2 oral hypoglycemic drugs still cannot make the blood glucose control satisfactory, the combination of 3 drugs can be considered, such as sulfonylurea + biguanide + α-glucosidase inhibitor, etc. However, when choosing the combination application scheme, it is necessary to consider both the combination of drugs with different hypoglycemic mechanisms of action and the characteristics, toxic and side effects, pharmacoeconomics and patient compliance of each type of drugs. In this way, the optimal efficacy of the combination regimen can be achieved.