Can I take Levothyroxine and Simvastatin together?
Drug interaction guide
Originally published 25 Jan 2026
Meets Patient’s editorial guidelines
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Taking these two medicines together is generally safe, but levothyroxine can affect how well simvastatin works. If your thyroid levels are not properly controlled (hypothyroidism), simvastatin may be less effective at lowering your cholesterol, and you may be at a slightly higher risk of muscle-related side effects from the statin.
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Why this happens
Thyroid hormones influence how the body processes cholesterol and how it metabolises statin medications. An underactive thyroid can lead to higher levels of fats in the blood and may slow down the breakdown of simvastatin in the body.
What you should do
You can take these medicines together, but ensure your doctor monitors your thyroid stimulating hormone (TSH) levels regularly. If your levothyroxine dose is changed, your doctor may also want to check your cholesterol levels or monitor you for any new muscle aches or pains.
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Using other medicines
Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.
Disclaimer
This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.
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Article history
The information on this page is written and peer reviewed by qualified clinicians.
25 Jan 2026 | Originally published
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