a composition useful for reducing serum glucose levels by an oral controlled release system and a method for treating diabetes in a human being by controlling the blood glucose level and reducing the complications associated with diabetic hyperglycemia and also the long term management of non - insulin dependent diabetes mellitus by avoiding the problems associated with the tight control of bgl , i . e ., hypoglycemia tolerance and seizures . the composition is directed to a solid , hydrophilic matrix controlled release oral dosage form where the dosage form contains a therapeutically effective amount of antidiabetic drug in the matrix ensuring complete bioavailability of the drug from the matrix of the tablet . the formulation undergoes substantially or approaches zero order release of active drug and the concentration of the excepients and the water swellable polymers is chosen in such a way that the erosion or dissolution rate of the polymer is equal to the swelling rate of the polymer to get a constant release . also , the concentration is chosen in such a way that the tablet will be fully dissolved at the same time the last of the drug is released and in addition a bioadhesive polymer may also be added to increase the residence time of the dosage form in the g . i . t . and at high concentration of the polymer , beta cyclodextrin may also be added to improve the release kinetics .