A meta-analysis of 21 studies examined incretin-based therapy as an add-on to metformin in patients with T2DM for 16–30 weeks; 7 studies used a short-acting GLP-1 receptor agonist (exenatide BID), 7 used longer acting GLP-1 receptor agonists (liraglutide or exenatide LAR), and 14 examined DPP-IV inhibitors. Here, GLP1R is linked to type 2 diabetes mellitus.