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Can I take Levothyroxine and Vitamin b12 together?

Drug interaction guide

There is no known direct interaction between levothyroxine and vitamin B12. They do not interfere with how each other works in the body, nor do they change how each other is absorbed or broken down.

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Why this happens

Levothyroxine is a synthetic thyroid hormone absorbed in the small intestine, while vitamin B12 (cobalamin) is absorbed further down in the ileum with the help of 'intrinsic factor'. They use different pathways for metabolism and excretion.

What you should do

You can safely take both levothyroxine and vitamin B12. However, for the best results, levothyroxine should be taken on an empty stomach, 30 to 60 minutes before breakfast. Vitamin B12 can be taken at the same time or later in the day with food. If your B12 supplement is part of a multivitamin containing calcium or iron, you must wait at least 4 hours after taking your levothyroxine before taking the supplement, as calcium and iron can block thyroid hormone absorption.

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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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