Although GLP-1 RAs and the dual GIP/GLP-1 RA tirzepatide are currently not approved for the treatment of T1D, growing evidence over the last few years has shown that these medications may serve as valid add-on treatments to insulin with substantial efficacy in improving glucose control, promoting weight loss and determining other beneficial effects (including preservation of residual beta-cell function) in patients with autoimmune diabetes. This evidence concerns the gene GCG and type 1 diabetes mellitus.