Is Iodine Safe with Selenium?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Do not self-supplement with both selenium and iodine concurrently without thyroid function monitoring. Consult your healthcare provider before combining these supplements, especially if you have an existing thyroid condition.
Why this interaction occurs
Selenium is essential for deiodinase enzymes that convert T4 to active T3. When selenium is deficient but iodine is supplemented, hydrogen peroxide accumulates in thyroid tissue causing oxidative damage. Conversely, adequate selenium protects against iodine-induced thyroid damage. Combined supplementation can unpredictably shift thyroid hormone levels, potentially triggering or worsening autoimmune thyroiditis (Hashimoto's or Graves' disease).
Evidence
Evidence level: strong.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 5,677 reports mentioning Selenium. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Selenium + 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 Iodine interactions → · All Selenium interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.