Abstract : The treatment of diabetes mellitus is complex and involves lifestyle modification to optimize nutrition and physical activity as well as the addition of pharmacological therapy to provide needed physiological support for insulin deficiency or for insulin resistance. Adherence to medical recommendations has been found to be associated with improved glycaemic control through HbA1c reduction but also to result in improved outcomes and reduced costs of diabetes. Despite this potential benefit of pharmacological therapy, adherence to glucose-lowering treatments is poor, ranging from 36% to 85% adherence to oral medications. The most common factors affecting medication taking in diabetic patients include regimen complexity, dosing frequency greater than twice daily, cost, poor self-confidence, insufficient education about the use of the products, depression, and adverse effects or fear of them. Several barriers to medication taking have been suggested although well-controlled trials to confirm and resolve these barriers are limited yet. Further studies are needed to test specific interventions to improve medication taking in diabetes.