Best Supplements for Thyroid Health: What Helps and What Can Harm
Iodine helps only if you're deficient, and too much can harm the thyroid. Selenium may lower Hashimoto's antibodies. See safety warnings and lab pitfalls.
By the editorial team · Updated Oct 14, 2026 · 3 sources cited
The best supplements for thyroid health are mostly about avoiding harm. Iodine is essential, but extra iodine or kelp can trigger thyroid problems in people who already get enough. Selenium lowered thyroid antibodies in Hashimoto's in some meta-analyses, without clear effects on symptoms. Biotin can make thyroid blood tests misleading, and calcium and iron block thyroid medication.
Evidence-ranked options
| Supplement | Evidence | Typical dose | Notes |
|---|---|---|---|
| Iodine (only if intake is low) | A | 150 mcg a day (220 mcg in pregnancy) | Use iodized salt or a prenatal; avoid kelp and high-dose products. |
| Selenium (Hashimoto's) | C | 100–200 mcg a day in studies | May lower antibodies; stay under 400 mcg a day. |
| Vitamin D (if low) | C | 600–2,000 IU | Low levels are common in autoimmune thyroid disease. |
| Thyroid 'support' blends | D | Not recommended | Some contain iodine, kelp or even thyroid hormone. |
A: strong · B: moderate · C: limited or mixed · D: good evidence of no benefit. See the evidence database.
Interactions to watch
| Supplement | Issue with thyroid treatment |
|---|---|
| Calcium, iron, magnesium | Block levothyroxine absorption; separate by 4 hours |
| Biotin | Can distort thyroid blood tests |
| Ashwagandha | May raise thyroid hormone levels |
| Kelp, iodine | Can trigger hyper- or hypothyroidism |
Check your list with our drug interaction lookup.
Ingredient guides
Frequently asked questions
Can supplements fix hypothyroidism?
No. Hypothyroidism is treated with thyroid hormone medication. Supplements can interfere with it.
When should I take supplements with levothyroxine?
Take calcium, iron and magnesium at least 4 hours apart from levothyroxine. Stop biotin before blood tests if your doctor advises.
Sources
Educational content, not medical advice. Read our medical disclaimer.