Levothyroxine and Warfarin: Drug Interaction Guide

Quick answer: This combination requires caution. Levothyroxine and Warfarin can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How Levothyroxine interacts with Warfarin

Levothyroxine can increase catabolism of vitamin K-dependent clotting factors as thyroid status normalizes. This may enhance warfarin anticoagulant effect.

What you should do

Monitor INR when starting, stopping, or changing levothyroxine dose and adjust warfarin accordingly.

Key facts

Severity

Moderate — caution required

Mechanism

Levothyroxine can increase catabolism of vitamin K-dependent clotting factors as thyroid status normalizes. This may enh...

Action

Monitor INR when starting, stopping, or changing levothyroxine dose and adjust warfarin accordingly.

Important medical disclaimer: This page provides educational information about drug interactions for general reference. It is not a substitute for professional medical advice, diagnosis, or treatment. Always discuss your specific medications with a qualified healthcare provider before starting, stopping, or changing any treatment. About our editorial team.

Frequently asked questions

Can I take Levothyroxine and Warfarin together?

With caution. Monitor INR when starting, stopping, or changing levothyroxine dose and adjust warfarin accordingly.

What is the severity of this interaction?

The interaction between Levothyroxine and Warfarin is classified as Moderate — caution required. Levothyroxine can increase catabolism of vitamin K-dependent clotting factors as thyroid status normalizes. This may enhance warfarin anticoagulant effect.

What should I do if I'm prescribed both?

Monitor INR when starting, stopping, or changing levothyroxine dose and adjust warfarin accordingly. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

Last reviewed: by iMedic Medical Editorial Team. Our editorial process.