- Low compliance to a prescribed Coumadin treatment can result in negative health outcomes. In this study we aimed to evaluate risk factors affecting patient compliance to Coumadin. For this purpose, two study phases were performed: Phase 1: a retrospective eight-year follow-up of databases from health care services; and Phase 2: a cross-sectional study with telephone interviews. A Total Compliance Index was constructed using the number of Coumadin purchases (40%), international standardised ratio (INR) tests (40%), and average INR values (20%). Multiple models for the Total Compliance Index were constructed using socio-demographic, treatment-related, and health care utilisation variables, use of drugs, patient-physician relationships and patient’s quality of life. 78.5 ± 3.4% of patients in the total population were non-compliant in the retrospective phase of the study, and 53.2% in the second, cross-sectional phase. Total Compliance Index was significantly associated with older age, number of doctor visits, and drugs from group C. We suggest that the Total Compliance Index for other drugs can be utilised as well.