Can I take Avastin and Levothyroxine together?
Drug interaction guide
Originally published 14 Mar 2026
Meets Patient’s editorial guidelines
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There is no known direct interaction between Avastin (bevacizumab) and levothyroxine. However, Avastin can sometimes affect how your thyroid gland works, which might change how much levothyroxine you need.
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Why this happens
Avastin is a type of targeted therapy that can occasionally cause an underactive thyroid (hypothyroidism) as a side effect. If this happens, your existing dose of levothyroxine may need to be adjusted by your doctor to keep your hormone levels balanced.
What you should do
Back to contentsYou can safely take these medicines together. While you are on Avastin, your medical team will likely perform regular blood tests to check your thyroid function. If you notice new symptoms like extreme tiredness, feeling cold, or unexplained weight gain, let your doctor know.
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Using other medicines
Back to contentsTaking 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.
14 Mar 2026 | Originally published
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