Bile acids are amphipathic water-soluble steroid-based molecules best known for their important lipid-solubilizing role in the assimilation of fat. Recently, bile acids have emerged as metabolic integrators with glucose-lowering potential. Among a variety of gluco-metabolic effects, bile acids have been demonstrated to modulate the secretion of the gut-derived incretin hormone glucagon-like peptide-1 (GLP-1), possibly via the transmembrane receptor Takeda G protein-coupled receptor 5 (TGR5) and the nuclear farnesoid X receptor (FXR), in intestinal L cell. The present article critically reviews current evidence connecting established glucose-lowering drugs to bile acid-induced GLP-1 secretion and discusses whether bile acid-induced GLP-1 secretion may constitute a new basis for understanding how metformin, inhibitors of the apical sodium-dependent bile acids transporter, and bile acid sequestrants - old, new and neglected glucose-lowering drugs - improve glucose metabolism.