This is the section every Hashimoto's sufferer wants — the supplements that might actually help. One has real trial evidence; several are worth a try; some are pointless; and a couple are actively dangerous. Here's the honest, graded rundown.
Selenium is the best-studied supplement in Hashimoto's: at ~200 mcg/day (as selenomethionine) it reliably lowers thyroid antibodies across many trials, with the biggest benefit in early, pregnant, or deficient people. The honest caveat: it moves the antibody number more reliably than it moves the disease, and it hasn't been shown to keep you off thyroid hormone. Don't exceed ~400 mcg (toxicity). Judge it by a 3–6 month antibody recheck. Evidence ●●●●○
A handful with real, if smaller, signals: myo-inositol + selenium (a combination that lowered TSH and antibodies in early/subclinical disease); black seed oil / Nigella sativa (2 g/day of the powdered seed dropped TSH and antibodies in one small trial); and bioavailable curcumin (lowered antibodies alongside an anti-inflammatory diet). All cheap, low-risk, one-good-study-each — reasonable experiments, not proven cures. Evidence ●●●○○
The least glamorous and often most effective step: check and correct vitamin D (to sufficiency), ferritin/iron (needed for thyroid hormone and energy, and commonly low in women), vitamin B12 (Hashimoto's overlaps with pernicious anaemia), and zinc (supports T4→T3 conversion). These treat the deficiencies that masquerade as 'thyroid symptoms' — and correcting them often does more than any exotic supplement. Evidence ●●●○○
Three to be wary of
High-dose iodine/kelp (worsens the disease), over-the-counter 'thyroid glandular' supplements (unregulated, and can contain real hidden hormone), and ashwagandha (it raises thyroid hormone — occasionally helpful in mild hypo, but it can tip you toward hyperthyroid and was never tested in antibody-positive patients). And L-tyrosine, marketed for thyroid, won't fix an autoimmune gland — skip it.
The Hashimoto’s Guide