The Iodine & Hashimoto’s Question

If you have Hashimoto’s, you may have heard conflicting advice about iodine. Your thyroid needs iodine to make thyroid hormones, yet too much iodine can also disrupt thyroid function, particularly in people with Hashimoto's, Graves', or other forms of thyroid dysfunction. (1,2)

So, is iodine good for Hashimoto’s? The answer is not simply yes or no. Getting enough iodine matters; however, more is not necessarily better. Your iodine intake, diet, supplements, thyroid function, and individual health needs all matter when finding the right balance.

Table of Contents

1. Why Iodine Matters for Thyroid Function
2. Is Iodine Good for Hashimoto’s?
3. What About Iodine Supplements for Thyroid Health?
4. How Much Iodine Do You Need?
5. Finding the Right Iodine Balance
6. FAQs

Why Iodine Matters for Thyroid Function

Iodine is an essential mineral your thyroid uses to make thyroid hormones. In simple terms, iodine becomes part of thyroxine (T4) and triiodothyronine (T3), the hormones your thyroid produces to help regulate metabolism and many other processes throughout your body. (2)

Both too little and too much iodine can interfere with thyroid function, although iodine deficiency is rare in the United States. (1,2)

If you want to understand Hashimoto’s more broadly, my guide to Hashimoto’s and thyroid health explains what happens when the immune system targets the thyroid.

Is Iodine Good for Hashimoto’s?

This is where the iodine and Hashimoto’s question becomes more nuanced. People with Hashimoto’s, Graves’, and other forms of thyroid dysfunction may be more sensitive to the effects of high iodine intake. Large amounts of iodine from iodine-rich medications, seaweeds (such as dulse and kelp), and supplements may cause or worsen hypothyroidism in susceptible individuals. (1)

Research also suggests that excess iodine intake may be associated with thyroid autoimmunity in susceptible populations, although the relationship depends on iodine status, population, and other individual factors. (3)

That does not mean iodine itself is “bad” for Hashimoto’s. Your thyroid still requires iodine. The goal is adequate intake without assuming that larger doses will provide greater thyroid support.

What About Iodine Supplements for Thyroid Health?

Iodine supplements for thyroid health deserve particular caution when you have Hashimoto’s. I do not recommend experimenting with high-dose iodine on your own.

The American Thyroid Association notes that there is no known thyroid benefit to routinely consuming iodine above the recommended daily allowance. It advises against iodine or kelp supplements containing more than 500 mcg of iodine per day and recommends that long-term intake above the upper limit be monitored by a physician. (4)

If you are considering an iodine-containing supplement, work with your healthcare professional to consider your diet, existing supplements, thyroid function, and individual iodine needs.

Iodine is also only one nutrient involved in thyroid health. I explain the roles of iodine, selenium, zinc, and iron in my guide to four essential nutrients for Hashimoto’s.

How Much Iodine Do You Need?

Here is how much iodine the National Institutes of Health recommends each day for adults. (2)

These numbers are population-level recommendations, not individualized prescriptions. Your needs may differ, particularly if you have Hashimoto’s, are pregnant or breastfeeding, take iodine-containing medications or supplements, or have other thyroid concerns.

Finding the Right Iodine Balance

When it comes to Hashimoto’s and iodine, I focus on balance rather than megadoses. Check how much iodine you already receive from foods, iodized salt, multivitamins, and other supplements before adding another source.

For daily nutritional support, I recommend the Essential 4 Supplements for everyone from 1 to 101 years old: a Complete Multivitamin, Fish Oils / Omega-3, Multi-Strain Probiotic, and Vitamin D with Vitamin K2. Count any multivitamin you take in your iodine total.

If you have Hashimoto’s and continue to experience symptoms, work with your healthcare professional to evaluate your thyroid function rather than adjusting iodine intake or supplemental thyroid hormone on your own. You can also read my guide to supplemental thyroid hormone and Hashimoto’s for more information.

Iodine is essential for thyroid function. With Hashimoto’s, however, the goal is not simply to get more. It is to get an appropriate amount for your individual needs while avoiding unnecessary excess.

FAQs

• Should I avoid iodine completely if I have Hashimoto’s?
  No. Your thyroid needs iodine to make thyroid hormones, whether or not you have Hashimoto’s. The concern is excess, not iodine itself. People with Hashimoto’s, Graves’, or other forms of thyroid dysfunction may be more sensitive to high intakes. (1,4) Aim for adequate intake, and work with your healthcare professional before cutting out iodine-rich foods or adding a supplement.
• Should I take iodine supplements if I have Hashimoto’s?
  Do not assume you need an iodine supplement simply because you have Hashimoto’s. Your appropriate intake depends on your diet, existing supplements, thyroid function, medications, pregnancy status, and other individual factors. Discuss supplementation with your healthcare professional before starting or substantially changing your iodine intake.
• Can too much iodine affect thyroid function?
  Yes. Excess iodine can contribute to thyroid dysfunction, and people with preexisting thyroid conditions can be particularly susceptible to its effects. (2,4) The adult tolerable upper intake level is 1,100 mcg per day from food and supplements combined, although individual medical circumstances can differ.
• What foods contain iodine?
  Common dietary sources include dairy products, eggs, iodized salt, seafood, and some breads. Seaweed can contain especially high and highly variable amounts of iodine, so more is not necessarily better if you have Hashimoto’s. (2)
• How do I know if I’m getting too much iodine?
  Start by adding up your sources, since supplement labels list iodine in mcg: dairy, iodized salt, multivitamins, seafood, seaweed, and other supplements. Urinary iodine tests are used to assess groups, yet results vary day to day and are less reliable for one person. (5) Your healthcare professional can evaluate your thyroid function and help you judge whether your intake fits your needs.

References

1. National Institute of Diabetes and Digestive and Kidney Diseases. “Hashimoto’s Disease.” NIDDK. https://www.niddk.nih.gov/health-information/endocrine-diseases/hashimotos-disease. Accessed on September 14, 2026.
2. National Institutes of Health, Office of Dietary Supplements. “Iodine: Fact Sheet for Health Professionals.” NIH Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/. Accessed on September 14, 2026.
3. Vargas-Uricoechea H, Castellanos-Pinedo A, Meza-Cabrera IA, et al. “Iodine Intake from Universal Salt Iodization Programs and Hashimoto’s Thyroiditis: A Systematic Review.” Diseases, May 23, 2025. https://pubmed.ncbi.nlm.nih.gov/40558577/. Accessed on September 14, 2026.
4. American Thyroid Association. “ATA Statement on the Potential Risks of Excess Iodine Ingestion and Exposure.” American Thyroid Association, June 5, 2013. https://www.thyroid.org/ata-statement-on-the-potential-risks-of-excess-iodine-ingestion-and-exposure/. Accessed on September 14, 2026.
5. Pearce EN, Caldwell KL. “Urinary Iodine, Thyroid Function, and Thyroglobulin as Biomarkers of Iodine Status.” The American Journal of Clinical Nutrition, August 17, 2016. https://pmc.ncbi.nlm.nih.gov/articles/PMC5004493/. Accessed on September 21, 2026.