This page explains what happens if Allopurinol and Warfarin are taken together, according to official sources.
Potential potentiation of warfarin effect
Allopurinol can enhance the effect of warfarin and increase INR in some individuals. INR should be monitored more frequently when starting or changing the dose of allopurinol.
Monitor INR more frequently when initiating or adjusting allopurinol, and observe for unusual bleeding.
Last updated: Sep 25, 2026
Before changing or stopping any medicine, ask your doctor or pharmacist. Never stop your medicine on your own.