GCG and type 2 diabetes mellitus: In fact, whether it is based on insulin sensitization and the use of first-line treatment drugs for T2DM, such as glitazones and metformin, or GLP-1 analogues and dipeptidyl peptidase inhibitors, which have been approved and marketed by the FDA in recent years, there are different degrees of toxic and side effects and blood sugar control failure in clinical practice.