Before starting rivaroxaban after stopping warfarin, what INR threshold is required?

• A. INR < 2
• B. INR < 2.5
• C. INR < 3
• D. INR < 1.5

Answer: (C)

When switching from warfarin to rivaroxaban, you want the lingering effects of warfarin to have faded enough so that starting the DOAC does not risk too much combined anticoagulation. The INR threshold used here is 3 or lower. The INR reflects how strongly warfarin is anticoagulating the patient; once it’s at or below 3, the residual warfarin effect is limited, and rivaroxaban can be added safely to provide rapid, consistent anticoagulation without a dangerous overlap. Starting rivaroxaban while the INR is higher would mean overlapping anticoagulant activity from both drugs, increasing bleeding risk. In practice, guidelines endorse initiating rivaroxaban after warfarin is stopped when the INR is ≤3.