Background Adherence to medication has an important role in the long-term management of diabetes. The Indonesian Endocrinologist Association found that of the 50% of the entire population who have been diagnosed with diabetes, two-thirds are undergoing therapy and only one-third have been achieving the intended outcomes of the drug therapy. This study aimed to identify patients' adherence behavior and the root causes of non-adherence. Methods This study used a non-experimental mixed-methods approach. A total of 40 patients with type 2 diabetes mellitus (T2DM), who were part of the referral program of the National Health Care Security System (BPJS Kesehatan) were recruited by purposive sampling from 17 primary health care centers in Surabaya, Indonesia. Results The adherence behavior assessment revealed non-adherence among 80% of the patients. The highest instances of non-adherence based on the percentage scores involved the following: patients forgot to take the medications (38.23%), patients preferred not to take the medications (20.59%) and the drug products were not available for the patient (14.71%). The factors influencing non-adherence included the complex instructions for taking medication, the absence of a reminder, the unwanted side effects of the drug, the feeling of repetition, the feeling that drugs were ineffective and the concern for the drug's effects on the kidney. Conclusions The high rates of non-adherence identified in this study encourage pharmacists to implement better medication therapy management for chronic diseases. The patients' understanding of drug therapy indications and regimens is very important in increasing the expectations of achieving effective treatment, awareness and concern for medication safety and treatment compliance.
Keywords: adherence behavior; medication therapy management; oral antidiabetics; primary health care.