Guide to Dietary Supplements and Thyroid Disease

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People with thyroid disease frequently use dietary and herbal supplements. But, there are many things to consider before taking these products.

Some may have benefits specifically for those who have hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). On the other hand, some products may interfere with the absorption of thyroid hormones. These side effects may complicate testing or pose other dangers.

Knowing more about some common supplements and their effect on thyroid disease can help you make the right choices for your overall health. This article explains supplements people commonly use to support the thyroid and how they may impact thyroid testing and your overall health.


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Common Thyroid Disease Supplements

Many supplements are commonly considered "healthy" for people with thyroid disease. That said, even supplements that may have benefits for some people could have potential risks for others. So, it's best to speak to a healthcare provider before adding these or any other options to your regimen.

Vitamin D

Low vitamin D levels are associated with an increased risk of developing autoimmune thyroid diseases such as Hashimoto's thyroiditis (when immune cells attack the thyroid) and Graves' disease (a condition that leads to thyroid hormone overproduction). Therefore, vitamin D supplements may be helpful for those with thyroid diseases.

In addition to prevention, a 2018 study found that vitamin D supplements improved TSH (thyroid stimulating hormone) levels in people with hypothyroidism.

Many people in the United States have low levels of vitamin D. Fortunately, a simple blood test can help you know whether you are deficient or not.

Be sure to talk to a healthcare provider about taking vitamin D, as an excess can lead to side effects such as painful kidney stones.

Vitamin B12

Vitamin B12 deficiency is relatively common, especially in people over age 50. Furthermore, the drug metformin, used as a treatment for concomitant insulin resistance in people with hypothyroidism, may reduce B12 levels.

The symptoms of vitamin B12 deficiency can mimic many of the symptoms of hypothyroidism, so a deficiency can be easy to miss.

Under-treated hypothyroidism and vitamin B12 deficiency are linked with an increased risk of stroke, even in young people, because vitamin B12 deficiency can increase homocysteine levels, which are a well-established risk factor for ischemic stroke. So, it's essential to make sure you receive adequate amounts of the vitamin.

You can find vitamin B12 in meat and animal products. But even with adequate food intake, some people, especially those with digestive conditions, may not absorb it well. In this situation, you may want to consider a supplement.

Conjugated Linoleic Acid (CLA)

Conjugated linoleic acid (CLA) is a fatty acid often used for weight loss. It is naturally found in dairy and beef and is also available in supplement form.

Thyroid disease can make it difficult to lose weight. Therefore, some people use CLA to support their weight loss goals. However, the evidence to support this practice is mixed. While some human studies have shown that CLA reduced fat mass, others have not found CLA alone or combined with exercise changed body composition.

CLA can cause gas and digestive upset in some people. If you are trying to lose weight with hypothyroidism, ask a healthcare provider for her recommendations.


Iodine is an element that helps the thyroid produce hormones. Therefore, striking the right balance with iodine is essential since too much or too little can contribute to thyroid problems.

Most people get adequate iodine through iodized salt. In addition, iodine is in some types of fish, milk, and eggs. It is also available in supplement form.

Iodine deficiency is extremely rare in the United States. Therefore taking iodine supplements may not only fail to help but could potentially make your condition worse. For that reason, there is significant controversy over iodine supplements and thyroid health, including the use of kelp supplements, which are high in this essential mineral.

The American Thyroid Association suggests avoiding daily consumption of dietary supplements with more than 500 micrograms of iodine.


Selenium is a mineral that is important in thyroid hormone metabolism. It is in seafood, beef, poultry, and eggs. Some foods are also fortified with selenium. In addition, you can take it in supplement form.

A 2018 study found that selenium supplementation may reduce levels of anti-thyroperoxidase (an enzyme in the thyroid) in people with autoimmune hypothyroidism. In addition, in those with Graves' disease, researchers noted improvements in thyroid antibodies and quality of life.

Selenium has a narrow "therapeutic window," meaning that even small excesses can be toxic.


Zinc is a mineral needed to produce thyroid hormones in the body. It is in animal proteins, nuts, and whole grains.

A 2018 study found that these supplements may benefit women with hypothyroidism who have excess weight and obesity. A zinc deficiency has been associated with hypothyroidism and other autoimmune diseases.

Thiamine (Vitamin B1)

There is some evidence that thiamine supplements may reduce fatigue in people with Hashimoto's thyroiditis. Thiamine is a B vitamin (B1) necessary for metabolism. It is in beans, lentils, fortified bread and cereals, and eggs.

If you have autoimmune thyroid diseases such as Hashimoto's disease and Graves' disease, you might not absorb thiamine properly, even with adequate intake. So people with thyroid disease may wish to talk to a healthcare provider about supplementation.


Since so many vitamins and minerals impact thyroid function, supplementation could benefit people with thyroid conditions. Always talk to a healthcare provider before starting them to be sure it makes sense in your situation.

Supplements That Affect Medications and Tests

Virtually any supplement or over-the-counter (OTC) medication may interact with your thyroid medications. For example, some may decrease the absorption of the synthetic form of thyroid hormone, levothyroxine, if taken within an hour of dosing. In addition, some supplements may cause problems even if taken later on.

supplements that interfere with thyroid medication
Illustration by Emily Roberts, Verywell

Calcium and Iron

You should take calcium and iron supplements at least three to four hours after levothyroxine to avoid reduced drug absorption. Both of these can bind to the medication in the gut, preventing its absorption and reducing its effectiveness.

"Green Food" Supplements

Many "green food" supplements contain large amounts of cruciferous vegetables, such as broccoli and spinach. Unfortunately, many of these otherwise healthy foods have goitrogens. These are substances that can disrupt thyroid function by inhibiting your body's ability to use iodine and interfering with thyroid hormone release.

Doctors do not recommend that people with thyroid disease avoid these healthy foods. Instead, it is wise to space them out in the diet and avoid supplements with concentrated amounts.


Biotin alone or as a component of B complex vitamins can interfere with the immunoassay (a lab technique used to determine TSH levels). That means that sometimes TSH may appear lower than it is. Biotin is a common ingredient in many supplements designed to improve hair, skin, and nails.


Some supplements may negatively interfere with thyroid medication or medical tests and increase certain health risks.

Supplements to Avoid

Some supplements are best avoided altogether by people who have thyroid disease.

Ashwagandha and Bladderwrack

Some herbal preparations may include ashwagandha (Indian ginseng) and bladderwrack (brown seaweed).

Ashwagandha comes from an evergreen shrub. In Ayurvedic medicine, it is used for stress. In traditional Chinese medicine, bladderwrack is used to treat thyroid disease.

There’s no credible evidence to show these herbs will help a thyroid problem, but they may interact with your thyroid medication. Bladderwrack may also have dangerously high levels of iodine.

"Thyroid Support" Supplements

There are several supplements that are labeled as providing "thyroid support" or "adrenal support" or that claim to be "thyroid boosters." The ingredients in these products vary and may include:

  • Vitamins
  • Minerals
  • Herbs
  • Thyroid hormone
  • Adrenal steroids

You should not use these supplements instead of prescription thyroid medications.

In addition, these products may cause problems when used with thyroid hormone replacement therapy. That's because when used along with prescription thyroid hormone replacement, OTC thyroid supplements could stimulate the thyroid too much.

Thyroid overstimulation can lead to hyperthyroidism. This condition, in turn, increases the risk of osteoporosis, atrial fibrillation (an abnormal heart rhythm that can lead to strokes or heart failure), and more.

A 2013 study looking at 10 commercially available thyroid support products found that most supplements contained clinically significant amounts of T3 and T4 thyroid hormones. In fact, in some cases, the doses exceed amounts typically prescribed to treat hypothyroidism. 

In addition, a 2016 study found that the amount of T3 in some supplements was high enough to cause thyrotoxicosis, an excess of thyroid hormone in the body, or even thyroid storm. A thyroid storm is a life-threatening situation in which the body releases extreme amounts of thyroid hormones.

Bovine Thyroid Extracts

Bovine thyroid extracts are made from the thyroid glands of cows. They are sold as dietary supplements. (These should not be confused with other thyroid hormone treatment options, such as Armour Thyroid.)

In addition to the risks of under-treated or over-treated hypothyroidism noted above, bovine extracts pose a slight chance of being exposed to bovine spongiform encephalopathy (BSE or mad cow disease) if the health of the animals used for the extracts isn’t known.


In 2004, the FDA prohibited the sale of dietary supplements containing the stimulant ephedra. However, some imported supplements and teas continue to contain this ingredient.

Ephedra is often marketed as a supplement for weight loss and energy. But unfortunately, the dangers of ephedra outweigh any benefits and could be particularly concerning for people with hyperthyroidism. That's because it could further increase heart rate and blood pressure and lead to other issues.

Adverse effects have occurred even in people who are young and healthy. They include:

  • High blood pressure
  • Strokes
  • Seizures
  • Death

Imported supplements may also contain other ingredients that the FDA doesn't consider safe. In addition, some of these ingredients' names may be unfamiliar.


Some supplements can be dangerous to take with thyroid conditions, even those marketed for use as thyroid supplements. That's because some have high levels of nutrients that may be toxic. Others may interfere with thyroid medication.

Questions to Ask About Any Supplement

If you consider taking any vitamin, mineral, or dietary supplement, talking to a healthcare provider and weighing the potential risks and benefits is essential. Questions you may wish to ask include:

  • What is the possible benefit of this supplement? Have any scientific studies documented this finding, or is it hearsay?
  • What are the potential side effects? What symptoms would alert you to a possible adverse effect?
  • How may the supplement interfere with other medications, including the absorption of levothyroxine? How long do you need to wait after taking levothyroxine before taking the supplement?
  • Should you take the supplement with or without food?
  • Will you need to have more frequent thyroid testing if you choose to take the supplement? How often?


There may be some benefits to taking supplements when you have a thyroid condition. However, supplements also carry risks. Specifically, they might interfere with your standard thyroid treatment. Therefore, it is always best to discuss taking supplements with a healthcare provider.

A Word From Verywell

If your healthcare provider is unfamiliar with supplements or herbal therapies, you can seek the advice of a naturopathic provider. Just be sure to keep the person treating your thyroid disease in the loop about what you discuss.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. Liontiris MI, Mazokopakis EE. A concise review of Hashimoto thyroiditis (HT) and the importance of iodine, selenium, vitamin D and gluten on the autoimmunity and dietary management of HT patients.Points that need more investigation. Hell J Nucl Med. 2017;20(1):51-56. doi:10.1967/s002449910507

  4. American Thyroid Association. American Thyroid Association (ATA) issues statement on the potential risks of excess iodine ingestion and exposure.

  5. Santos, L., Neves, C., Melo, M., and P. Soares. Selenium and selenoproteins in immune-mediated thyroid disorders. Diagnostics. 2018. 8(4):pii:E70. doi:10.3390/diagnostics8040070

  6. Sanna, A., Firinu, D., Zarattari, P., and P. Valero. Zinc status and autoimmunity: A systematic review and meta-analysis. Nutrients. 2018. 10(1):68.

  7. Colon PJ, Greene DN. Biotin interference in clinical immunoassays. Jrnl App Lab Med. 2018;2(6):941-951. doi:10.1373/jalm.2017.024257

  8. National Library of Medicine. Fucus vesiculosus.

  9. Kang, G., Parks, J., Fileta, B. et al. Thyroxine and triiodothyronine content in commercially available thyroid health supplements. Thyroid. 2013. 23(10):1233-1237. doi/10.1089/thy.2013.0101

  10. Han, S., Eisenberg, M., Larson, P., and J. DiStefano. THYROSIM app for education and research predicts potential health risks of over-the-counter thyroid supplements. Thyroid. 2016. 26(4):489-498. doi:10.1089/thy.2015.0373

Additional Reading
  • Braverman, L, Cooper D. Werner & Ingbar's The Thyroid, 10th Edition. WLL/Wolters Kluwer; 2012.

By Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."