OBJECTIVES: Medications are used to improve quality of life, extend life expectancy and mitigate disease. Low adherence to antidiabetic drugs leads to increased diabetes complications and hospitalizations.  This in turn is associated with increase in health care costs and poor outcomes. Understanding barriers to adherence to medications will help to identify interventions to increase adherence and improve outcomes. Using a systematic literature review, this study summarizes and evaluates the published evidence in association with patient related barrier to medication adherence in type 2 Diabetic patients. METHODS: A comprehensive search of PubMed, MEDLINE and the Cochrane Database of Systematic Reviews from 2006-2015 was performed. The search was limited to articles published in English. Titles and the abstracts of the studies were screened by two independent reviewers and selected based on patient related barriers to medication adherence seen in patients with type 2 diabetes.  RESULTS: From 548 papers identified, 9 met inclusion criteria and were included in this systematic review. 461 abstracts were eliminated since the titles and abstracts were not indicative of patient barriers and medication adherence. 78 were excluded since the studies were not conducted in the United States. Two levels of barriers were observed: internal and external. The internal barriers constituted patient attributes such as poor health literacy (77.7%), denial of the disease (66.66%), inability to access healthcare and cultural beliefs and attitudes (22.22%).  External barriers such as lack of communication between health care providers (66.66%) and cost (33.33%) were seen as major barriers post health literacy. CONCLUSIONS: Health literacy and communication barriers were perceived as major barriers to medication adherence. Healthcare providers can play an important role in overcoming these barriers by counselling patients regarding medication adherence. Further research assessing innovative interventions that may resolve these barriers is needed.