GCG and type 2 diabetes mellitus: Compared with the previously published articles, thecontents and purposes of this review are different: (1) Focusing on the therapeutic roles of GLP-1RAs in T2DM, the multiple pathways by which GLP-1 regulates blood glucose are described in a more comprehensive and in-depth manner at the mechanism level; (2) The action characteristics of various types of non-insulin hypoglycemic drugs are compared, as well as the advantages, shortcomings, points for attention and challenges of GLP-1RAs in treatment.