Drug interactions
levothyroxine + multivitamin with minerals
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Polyvalent cations (e.g., calcium, iron, magnesium) in multivitamins reduce levothyroxine absorption, potentially leading to inadequate thyroid replacement and increased TSH.
Mechanism of action
Divalent/trivalent cations chelate/adsorb levothyroxine in the GI tract, decreasing bioavailability.
Clinical management
Avoid coadministration; separate levothyroxine and mineral-containing supplements by at least 4 hours. Monitor TSH 6–8 weeks after starting/stopping or changing the supplement; adjust levothyroxine dose as needed.
Drug reference
References
- EUTHYROX (levothyroxine sodium) tablets, Prescribing Information — FDA Label
- Levothyroxine: Drug Information — Lexicomp
- Levothyroxine: Drug interactions — UpToDate
Frequently asked questions
Can I take levothyroxine with multivitamin with minerals?
The interaction is rated: Moderate. Polyvalent cations (e.g., calcium, iron, magnesium) in multivitamins reduce levothyroxine absorption, potentially leading to inadequate thyroid replacement and increased TSH.
How serious is the interaction between levothyroxine and multivitamin with minerals?
The interaction is rated: Moderate. Evidence level: High.
How is the interaction between levothyroxine and multivitamin with minerals managed?
Avoid coadministration; separate levothyroxine and mineral-containing supplements by at least 4 hours. Monitor TSH 6–8 weeks after starting/stopping or changing the supplement; adjust levothyroxine dose as needed.
Why do levothyroxine and multivitamin with minerals interact?
Divalent/trivalent cations chelate/adsorb levothyroxine in the GI tract, decreasing bioavailability.
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