Metformin hydrochloride, a biguanide, is an effective treatment for type 2 diabetes, lowering both basal and postprandial hyperglycemia either as monotherapy or in combination with other antihyperglycemic drugs. Metformin hydrochloride in its immediate release form (IR) has been used for decades in the treatment of type 2 diabetes. An IR formulation releases the entire drug within 1-2 h after dosing, resulting in high drug concentrations in the GI (gastrointestinal) tract which may be associated with GI side effects (especially nausea, diarrhea) in 20-30% patients. This can limit the tolerated dose, reduce adherence and result in discontinuation of therapy. In addition, the frequent need to administer metformin two or three times daily may also not support good adherence to therapy.