A PHARMACEUTICAL COMPOSITION COMPRISING A COMBINATION OF (A) A 1-THIO-D-GLUCITOL COMPOUND REPRESENTED BY THE GENERAL FORMULA (I) AND (B) AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF BIGUANIDES, INSULIN SECRETAGOGUES, INSULIN SENSITIZERS, INSULINS, DIPEPTIDYL PEPTIDASE IV INHIBITORS, α-GLUCOSIDASE INHIBITORS, AND GLP-I MIMETICS, HAS SUPERIOR EFFICACY IN PREVENTING OR TREATING DIABETES MELLITUS, DISEASES ASSOCIATED WITH DIABETES MELLITUS, OR COMPLICATIONS OF DIABETES MELLITUS AND YET IT CAUSES NO APPRECIABLE SIDE EFFECTS.