Objective: Warfarin use is difficult due to the necessity for regular international normalized ratio (INR) monitoring and drug– drug interaction. However, it is still the most widely preferred oral anticoagulant. This study aimed to assess the efficacy andreliability of warfarin use by patients attending outpatient clinics (OC) or who received home health services (HHS). Materials and Methods: This study included 204 patients followed by OC and HHS and receiving warfarin treatment.Demographic and clinical characteristics and INR monitoring frequency were evaluated. Moreover, complications wereretrospectively questioned. The interactions between warfarin use and other medications were assessed. Hypertension,Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile INR, Elderly, Drugs/alcohol (HAS-BLED)and Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) scores were calculated in the atrial fibrillation (AF) group. Results: The patients followed by HHS were older (78 vs. 68, p<0.001). Cerebrovascular disease was more frequent in theHSS group (51% vs. 29.4%, p=0.002) while AF was more common in the OC group (65.7% vs. 43.1%, p=0.001). Patientswith an INR level in the subtherapeutic range were more common in the HHS group (42.2% vs. 24.5%, p=0.025), and throm boembolic complications were also observed more frequently (14.7% versus 10.8%, p=0.013). More than half of the individu als using drugs interacted with warfarin. In AF subgroup, the HAS-BLED and ATRIA scores were higher for HHS group com pared with the OC group [HAS-BLED, 2 (1–4) vs. 2 (0–5); ATRIA, 5 (1–7) vs. 2 (0–7); p=0.032 and p<0.001, respectively]. Conclusion: The current study showed that HHS and OC staff should regularly monitor patients’ INR levels and pay atten tion to drug–drug interactions to reduce complication