Is Selenium Safe with Cytomel?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Nutritional doses of selenium are considered safe with Cytomel. Avoid megadose selenium supplementation. Discuss with your provider if using selenium for autoimmune thyroid conditions alongside Cytomel therapy.
Why this interaction occurs
Cytomel provides exogenous T3, so selenium's role in T4-to-T3 conversion via deiodinase enzymes has limited direct pharmacokinetic impact. However, selenium status can influence overall thyroid autoimmunity and peripheral hormone metabolism, which may have subtle effects on clinical outcomes.
Evidence
Evidence level: limited.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 5,450 reports mentioning Cytomel. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Cytomel + 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 Cytomel interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.