Type 2 diabetes mellitus (T2DM) defined as a disease in metabolic, known with increased levels of blood glucose caused by insulin resistance. The etiology of T2DM causing hyperglycemia is a built up from a multifactorial complex process, starting from insulin resistance alongside relative insulin deficiency developing into predominant insulin secretory defect alongside with insulin resistance. It is acting as an international obstacle. Patients are treated by consuming medications targeting glycemic control. However, poor adherence in diabetes is known to be one of the main problems. Patients adherence could be affected by many factors both external and internal. It could be viewed as the patients willingness to follow the health care instructions to manage the disease. This article aims to review studies regarding T2DM patients adherence towards OAD.