Can I take thyroid supplements if I'm on levothyroxine?

Some interactions exist. Take calcium, iron, and high-dose ashwagandha at least 4 hours apart from levothyroxine. Consult your endocrinologist before adding iodine.

Will iodine cure hypothyroidism?

Only if your hypothyroidism is caused by iodine deficiency, which is rare in developed countries. Hashimoto's-driven hypothyroidism can actually worsen with high iodine intake.

What's the relationship between selenium and Hashimoto's?

A 2010 meta-analysis found selenium supplementation reduced thyroid peroxidase antibody levels in Hashimoto's patients. Effect on thyroid function itself is less clear.

Can thyroid supplements cause weight loss?

Not directly. If you have untreated hypothyroidism causing weight gain, correcting it with prescribed medication restores normal metabolism. Supplements alone rarely produce meaningful weight changes.

Are these safe during pregnancy?

Iodine at 150 to 220 mcg/day is recommended in pregnancy. Selenium, tyrosine, and ashwagandha should be used only under physician guidance during pregnancy.

Updated October 2026Expert Reviewed

Best Thyroid Supplements 2026

Two formulas. Selenium matters for thyroid function, and its safety window is narrower than most labels suggest.

Disclosure: we may earn a commission if you buy through links on this page, at no extra cost to you. Commissions differ by product, which is why the ranking policy is published: the score decides the band a product sits in, and nothing we earn can move it past a better-scoring one.

Ranking changes(Changed August 15, 2026)

August 15, 2026 Every score was recomputed from the published methodology, because the previous scores could not be reproduced from the stated criteria. The order changed in 16 of 31 categories. At the same time the ranking policy moved to published merit bands: the score decides the band, and nothing commercial can move a product past a better-scoring one.

Quick Comparison: Top 2

#	Read full review	Best For	Doses published	$/day	Check Price
1	Thyrafemme Balance	Women with normal thyroid tests and low iodine intake, not on thyroid medication	No	$1.63/day	Check Best Price
2	Thyrolin	Thyroid Support	No	$1.90/day	Check Best Price

Top Thyroid Supplements

#1Editor’s Choice$1.63/day

Thyrafemme Balance

A women's thyroid-support capsule with

Our score3.7/5Good

Best forWomen with normal

The label is published and selenium is at a research-level dose, but ashwagandha is advised against in thyroid disorders

Thyrolin

Natural thyroid function support formula

Our score3.5/5Good

Best forThyroid Support

Thyrolin provides comprehensive support for healthy thyroid function.

What these thyroid supplements are built on

Scores are easy to publish and impossible to check. So here is the same ranking from the other direction: the ingredients these 2 products are actually built on, and what the trials say about each one. Follow any of them to the evidence.

Ingredients with an established effective dose

These have a dose the research settled on, which means you can check a label against something. 2 of the 2 products below are built on two or more of them.

Ashwagandha — in 2 of the products here
Selenium — in 2 of the products here
Zinc — in 2 of the products here

Ingredients we would not pay extra for

These turn up across the category without a settled effective dose behind them. That does not make them useless; it means a product should not cost more because it contains them.

L-Tyrosine ×1
Iodine ×1

Buying Guide

How to Choose a Thyroid Supplement

No supplement replaces thyroid medicine. The American Thyroid Association (ATA) says hypothyroidism is treated with a daily thyroid hormone pill (levothyroxine) and advises stopping it only with your doctor's help. It also advises telling your doctor if you start or stop biotin, calcium or iron supplements, because they can affect your treatment or your test results.

Ingredients with evidence

Iodine: your thyroid needs it, and adults need 150 mcg a day. The ATA says the US diet generally provides enough and that routine doses above this have no known thyroid benefit. More than 1,100 mcg a day may cause thyroid problems. People with existing thyroid disease are more susceptible.
Selenium: in Hashimoto's thyroiditis, a 2024 meta-analysis of 35 studies found that selenium lowered thyroid antibodies. In people not taking thyroid hormone, it also slightly lowered TSH. Certainty was moderate. An earlier Cochrane review called the evidence incomplete and said the clinical relevance of lower antibodies is unclear. Trials often used 200 mcg a day, and the NHS says 350 mcg or less a day from supplements is unlikely to cause harm. See our selenium page.
Ashwagandha: in one 8-week trial of 50 people with subclinical hypothyroidism, 600 mg a day improved TSH, T3 and T4. However, NCCIH does not recommend ashwagandha for people with thyroid or autoimmune disorders, and it may interact with thyroid medicines. Use it only if your doctor agrees. See our ashwagandha page.
Tyrosine: we found no human trial showing that supplements change thyroid hormone levels.

Red flags to avoid

Kelp or iodine products providing more than 500 mcg a day. The ATA advises against them and notes that some contain several thousand times the safe upper limit.
"Thyroid support" or "glandular" products that may contain real hormone. In a 2013 lab test of 10 thyroid supplements, 9 contained detectable T3. Some delivered more T3 or T4 than doses used to treat hypothyroidism, which can cause an overactive thyroid.
Biotin before blood tests. The ATA says biotin can make thyroid tests look abnormal when they are normal, and advises stopping it 2 days before blood is drawn.
Any product that suggests you can cut or stop levothyroxine.
Proprietary "thyroid complexes" that hide their ingredients or doses.

How to use this ranking

Get a diagnosis with blood tests before buying anything. If you choose a supplement, pick a third-party-tested product with every dose disclosed and iodine and selenium within the limits above. Tell your doctor, who may want to recheck your thyroid levels.

Sources:

Our Methodology

Thyroid supplements require extra scrutiny because of documented cases of adulteration with thyroid hormones. We prioritize third-party testing, safe iodine levels (at or near 150 mcg RDA), selenium forms, and clear labeling that the product does not replace prescribed thyroid medication. Products encouraging medication cessation are flagged.

Frequently Asked Questions

Guides on this topic

Goals and pathways connected to this category, buyers often compare across these.

Medical Disclaimer

The content on this page is for informational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult your physician or qualified healthcare provider before starting any new supplement regimen. Individual results may vary.