DPP-4 inhibitor is a new type of oral hypoglycemic drug that elevates endogenous GLP-1 levels by inhibiting the activity of dipeptidyl peptidase 4 (DPP-4), an important enzyme that inactivates endogenous glucagon-like peptide-1 (GLP-1). It can lower blood glucose through the following effects: 1. GLP-1 can glucose-dependently promote insulin secretion to lower blood glucose, and hypoglycemia does not occur when applied alone. 2. GLP-1 can inhibit glucagon secretion from pancreatic alpha cells to further lower blood glucose. 3. It can weaken gastrointestinal motility, delay gastric emptying, and enhance satiety. 4. DPP-4 inhibitor alone does not cause hypoglycemia, and can be used in combination with other oral hypoglycemic drugs, or in combination with insulin.