Is Selenium Safe with Liothyronine?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Discuss selenium supplementation with your provider. Do not self-supplement above 200 mcg/day. Selenium status should be assessed in patients with ongoing thyroid dysfunction.
Why this interaction occurs
Selenium is an essential cofactor for deiodinase enzymes (particularly type 1 and type 2) responsible for converting inactive T4 to active T3. In patients on liothyronine (T3) therapy, selenium deficiency may impair residual endogenous thyroid hormone metabolism. Excess selenium (>400 mcg/day) is toxic and can paradoxically impair thyroid function. Adequate selenium is especially relevant in autoimmune thyroid disease (Hashimoto's) where it may reduce thyroid peroxidase antibodies.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 8,329 reports mentioning Liothyronine. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Liothyronine + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Selenium interactions → · All Liothyronine interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.