This page explains what happens if Metronidazole and Warfarin are taken together, according to official sources.
Dangerous spike in warfarin levels and INR
Metronidazole strongly impairs hepatic metabolism of warfarin, dramatically spiking INR and creating an immediate risk of major hemorrhage.
Anticipate a 30-50% warfarin dose reduction when metronidazole is initiated. Monitor INR within 48-72 hours.
Talk to your doctor or pharmacist about these two medicines; don't stop a prescribed medicine on your own.
Last updated: Sep 25, 2026
Before changing or stopping any medicine, ask your doctor or pharmacist. Never stop your medicine on your own.