What is the interval for monitoring warfarin therapy once therapeutic levels are achieved?

Abstract

The international normalized ratio (INR) should be measured monthly once therapeutic levels are achieved and are stable for at least 8 weeks, although treatment should be individualized and an increased frequency may be required by some patients (strength of recommendation [SOR]: C, consensus statements). For highly compliant patients with stable levels and a clear understanding of factors that influence anticoagulation (changes in health, diet, medications), routine monitoring may be extended to 6 weeks (SOR: B, single randomized controlled trial [RCT]) or longer (SOR: C, case series). Patient-managed warfarin therapy, using biweekly self-measurements, results in more time in therapeutic range than routine physicianmanaged care (SOR: A, RCTs).