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Can I take Colecalciferol and Levothyroxine together?

Drug interaction guide

Taking colecalciferol (Vitamin D3) and levothyroxine together is generally safe, but there is a small possibility that high doses of Vitamin D could affect how your thyroid medication works. Specifically, if Vitamin D significantly raises your calcium levels, it might change how your body responds to levothyroxine.

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Why this happens

There is no direct evidence that Vitamin D stops levothyroxine from being absorbed. However, Vitamin D helps the body absorb calcium. If calcium levels in the blood become very high (hypercalcaemia), it can theoretically alter thyroid hormone sensitivity or metabolism. Additionally, if you take Vitamin D as part of a combined calcium supplement, the calcium itself will block the absorption of levothyroxine.

What you should do

You can take these two medications together. To be safe, it is best to take levothyroxine on an empty stomach, at least 30 to 60 minutes before breakfast or any other medications. If your Vitamin D supplement also contains calcium, you must wait at least 4 hours after taking your levothyroxine before taking the supplement. Your doctor will monitor your thyroid levels (TSH) as part of your routine care.

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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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