iodine and thyroid medication

Iodine supplementation can destabilize thyroid

What's happening

Both excess and deficient iodine affect thyroid function. High-dose iodine supplements can cause thyroid dysfunction in susceptible individuals, including those on thyroid medication. Kelp supplements often contain unpredictable iodine amounts.

Recommendation

Avoid high-dose iodine or kelp supplements on thyroid medication. Discuss iodine status with your doctor.

Timing

Avoid iodine supplements unless medically supervised

Sources

— New England Journal of Medicine
— PMID: 9588628
— PMID: 24576895

Frequently Asked Questions

Can I take iodine and thyroid medication together?

Iodine supplementation can destabilize thyroid. Avoid high-dose iodine or kelp supplements on thyroid medication. Discuss iodine status with your doctor.

How should I time iodine and thyroid medication?

Avoid iodine supplements unless medically supervised

Is this interaction dangerous?

This interaction is rated “Warning” by Formulate. Both excess and deficient iodine affect thyroid function. High-dose iodine supplements can cause thyroid dysfunction in susceptible individuals, including those on thyroid medication. Kelp supplements often contain unpredictable iodine amounts.

Learn more about each substance

Mineral
Iodine
Dose, mechanism, evidence, safety →

Cited research

Studies from our registry that mention iodine or thyroid medication. Each links to the primary source and the other Formulate pages citing it.

Mentions thyroid medication · 2026
Memorial Sloan Kettering Integrative Medicine Monograph: Ashwagandha
Primary literature · Monograph
Documents thyrotoxicosis case reports associated with ashwagandha use. States ashwagandha may increase thyroxine levels. Also notes CYP3A4 induction (moderate) and sedative-additive effects. Does not give a hard avoid-with-levothyroxine warning but flags thyroid monitoring.

Other interactions to know

More interactions involving iodine or thyroid medication

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Medical disclaimer. This page is for educational purposes only and does not replace advice from a qualified healthcare provider.

Last medically reviewed: April 21, 2026

iodine↔thyroid medication