Drug interactions
Heparin + Levothyroxine
Severity: Minor
Heparin and Levothyroxine: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Thyroid hormone can increase the catabolism of vitamin K-dependent clotting factors, which strongly enhances warfarin. With heparin, the effect is small and inconsistent, and the clinical relevance is limited.
What this interaction means in plain words
Heparin and Levothyroxine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Heparin belongs to Cardiovascular; Levothyroxine belongs to Endocrine.
Why it happens
Possible modest pharmacodynamic enhancement; the well-known thyroid hormone effect applies mainly to vitamin K antagonists.
What to do
No dose change is usually needed; monitor aPTT or anti-Xa as usual when starting or adjusting levothyroxine.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Heparin
- Defibrotide + Heparin Contraindicated
- Heparin + Ketorolac Contraindicated
- Heparin + Oritavancin Contraindicated
- Acemetacin + Heparin Major
- Acetylsalicylic acid + Heparin Major
- Alteplase + Heparin Major
Other interactions of Levothyroxine
Frequently asked questions
Can I take Heparin with Levothyroxine?
MediHelp rates the interaction as minor. Heparin and Levothyroxine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Thyroid hormone can increase the catabolism of vitamin K-dependent clotting factors, which strongly enhances warfarin. With heparin, the effect is small and inconsistent, and the clinical relevance is limited.
How serious is the interaction between Heparin and Levothyroxine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No dose change is usually needed; monitor aPTT or anti-Xa as usual when starting or adjusting levothyroxine.
What other medicines interact with Heparin?
MediHelp also lists interactions of Heparin with, for example, Defibrotide, Ketorolac, Oritavancin. The full list is on the Heparin page.
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