An oral dosage form of an antidiabetic pharmaceutical composition comprises a core portion, an outer portion, and a controlled membrane film sandwiched therebetween. The core portion comprises metformin and a release-preventing agent. The controlled membrane film is provided with at least one passageway. The outer portion comprises a non-biguanide antidiabetic agent. In the oral dosage form, the metformin has a dissolution profile such that upon dissolving in a medium with a pH of approximately 6.8 at approximately 37° C., less than 15% is released from the oral dosage form at 2 hours, approximately 60-70% is released at 12 hours, and more than 80% is released at 20 hours. Upon a single-dose oral administration, the time that the oral dosage form provides a maximum plasma concentration of the metformin in a subject is from approximately 8 to 20 hours after administration.