Supplements for Thyroid: What Helps and What Can Harm

Feeling tired, cold, or foggy? Your thyroid could be part of the problem, and some supplements can help — but others can make things worse. This short guide gives clear, practical tips on common supplements people use for thyroid health, safe dose ranges, and the key warnings you need to know.

Key supplements that can help

Selenium — Typical daily doses range from 55 to 200 mcg. Selenium supports thyroid hormone conversion and, in some trials, has lowered anti-thyroid antibody levels in people with autoimmune thyroiditis. Don’t take high doses long term without a doctor’s okay.

Iodine — The RDA is about 150 mcg/day for adults. Iodine is essential for making thyroid hormones, but too much can trigger or worsen autoimmune thyroid problems and hyperthyroidism. Use iodine only if tests show a deficiency or your doctor recommends it.

Vitamin D3 — Many people with thyroid issues are low in vitamin D. Common supplement doses range from 1,000 to 4,000 IU/day depending on blood levels. Aim for a doctor-recommended target (often 30–50 ng/mL) rather than guessing.

Iron — Low iron or low ferritin can make hypothyroid symptoms worse and reduce response to thyroid meds. Treat low iron based on labs. A standard over-the-counter option is ferrous sulfate (check how much elemental iron you get) but consult a provider before starting.

Vitamin B12 — Deficiency is common with thyroid disease. Typical oral doses for replacement are in the hundreds to 1,000 mcg daily depending on how low your levels are. Injections may be used for severe deficiency.

Zinc and Tyrosine — Zinc helps thyroid hormone production; daily zinc often stays under 40 mg to avoid toxicity. L-tyrosine is an amino acid used by the thyroid; people use 500–1,000 mg, but evidence is limited. Use these only after reviewing your whole picture with a clinician.

Warnings, dosing, and interactions

Get tests first: TSH, free T4, free T3, anti-TPO/anti-thyroglobulin, ferritin, vitamin D, and B12. Don’t guess. Supplements can change labs and symptoms.

Timing matters: Levothyroxine and other thyroid meds are absorbed poorly with calcium, iron, soy, and high-fiber meals. Take thyroid medicine on an empty stomach and avoid calcium or iron within four hours.

Be careful with iodine and autoimmune disease — extra iodine can trigger flares in some people. Selenium can help autoimmune thyroiditis in some studies, but too much selenium causes problems. High-dose zinc long-term can cause copper deficiency.

Quality counts: Use third-party tested brands and avoid mega-doses unless supervised. If you’re pregnant, breastfeeding, or on multiple meds, check with your provider before starting anything new.

If you want practical next steps: get baseline blood tests, discuss results with your clinician, choose one or two targeted supplements based on deficits, and recheck labs after 8–12 weeks. Small, guided changes beat guessing. If symptoms persist, follow up with your provider for medication or referral.