Disclosed is a composition comprising a combination of (A)(1S)-1,5-anhydro-1-[5-(4-ethoxybenzyl)-2-methoxy-4-methylphenyl]-1-thio-D-glucitol and or a pharmaceutically acceptable salt thereof or a hydrate of the compound or the salt； and (B) an insulin secretagogue selected from the group consisting of glipizide, glibenclamide, and glimepiride, for preventing or treating diabetes mellitus, diseases associated with diabetes mellitus, or complications of diabetes mellitus.
