1,1-Dimethylbiguanide hydrochloride (metformin) is a strong base. It forms well defined salts and possessing excellent coordination capacity with transition metals, forming highly colored bidentate chelate complexes. Metformin (MET) exists in various forms: diprotonated (H2MET)2+ in strong acidic solution, monoprotonated (HMET)+ in weak acid, MET in neutral and deprotonated (MET)- in strong alkali solution. It is an oral antidiabetic drug. Pharmacokinetics of metformin has been studied. Determination of metformin in human plasma has been described by simple HPLC-UV method. Metformin is reported to increase plasma active glucagon-like peptide-1 (GLP-1) in humans.