Is Iron Safe with Cytomel?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Take Cytomel at least 4 hours before or after iron supplements. Monitor thyroid function tests more frequently if iron supplementation is initiated or discontinued.
Why this interaction occurs
Ferrous sulfate and other iron salts chelate with T3 (liothyronine) in the gastrointestinal tract, forming insoluble complexes that are poorly absorbed. This interaction can reduce thyroid hormone bioavailability and destabilize thyroid hormone levels.
Evidence
Evidence level: strong.
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 Iron interactions → · All Cytomel interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.