The chronic metabolic disorder diabetes mellitus is a fast-growing global problem with huge social, health, and economic consequences. It is estimated that in 2010 there were globally 285 million people(approximately 6.4% of the adult population) suffering from this disease. Therefore, the aim of the study was to determine DM patient's Adherence to therapeutic regimen. Methods A descriptive –correlational design will be used in the study. Barriers of diabetic patients' adherence to therapeutic regimen was designed after the literature review. Convenient sample of this study composed of 100 adult patients of both sexes who met inclusion criteria using standard questionnaires were studied to determine the demographic characteristics, medical history and the patients' barriers of adherence. Results The results revealed that the majority of patients about (53.1% ) forget their medication as a barrier to adherence to medication. About (28.1 %) cannot adhere to medication due to medication cost and only about (18.8 % ) of them use medication when feeling ill. . About (66.7 %) of patients with type II diabetes mellitus cannot stop smoking due to life stresses and about (33.3 %) of them have no desire to stop it. The majority of patients cannot adhere to follow up due to transportation difficulties about ( 94.7 %),and about ( 2.6 %) of patients cannot adhere to follow up due to lack of waiting places and long waiting time . The majority of patients about (77.5 %) can not adhere to diatary regimen because they are not prepared to change their habits in diet ,and about (2.5 %) can not adhere to dietary regimen because they use it only when feeling ill and also about (2.5 %) can not adhere to dietary regimen because no one tell them about the food that they have to avoid. The majority of patients (68.8 %) can not adhere to exercise due to inability to practice exercise and about (3.1% ) cannot adhere to exercise because there is no suitable place for practice .