The short answer
Clinical guidance recommends keeping oral iron and liothyronine at least four hours apart. This is a precaution against reduced thyroid-medicine absorption; an exact effect size for liothyronine and each iron preparation has not been established in the sources checked.
What this answer covers
Oral liothyronine sodium tablets with oral iron preparations. The intestinal absorption precaution does not apply to an iron infusion in the same way.
- Supplement or preparation
- Iron
- Medication ingredient
- liothyronine
What is the concern?
The Alberta medication monograph lists iron among products that can reduce liothyronine absorption. Australian Red Cross Lifeblood also specifically includes liothyronine in its oral-iron interaction guidance. Neither source supplies a direct T3 absorption experiment that quantifies the effect.
What interval is supported?
Alberta advises at least four hours before or after liothyronine; Lifeblood advises four to five hours. Use the schedule set by the prescriber or pharmacist, especially when iron is prescribed for a diagnosed deficiency or several thyroid doses are taken each day.
What should I check on the bottle?
Record the iron preparation, dose and whether it is part of a prenatal or multivitamin. Combination ingredients can add scheduling considerations. Do not assume a low-dose or alternative iron formulation has been proved exempt, and do not extend the oral timing rule to intravenous iron without considering its different route.
Should I change either prescription?
A spacing precaution is not a reason to stop prescribed iron or adjust liothyronine without review. Thyroid dosing uses symptoms and laboratory results. The current Cytomel label does not specifically name iron in its absorption table, so the strength of this article remains guidance-based rather than a measured T3 interaction.
Evidence and practical considerations
Absorption & effectiveness
Clinical guidance recommends keeping oral iron and liothyronine at least four hours apart. This is a precaution against reduced thyroid-medicine absorption; an exact effect size for liothyronine and each iron preparation has not been established in the sources checked.
- Exact scope
- Oral liothyronine sodium tablets with oral iron preparations. The intestinal absorption precaution does not apply to an iron infusion in the same way. with oral liothyronine sodium providing the exact liothyronine active moiety
- Medication form and route
- oral
- Timing or duration
- During co-use; study-specific durations are retained in the source summaries. No universal duration or dose-response inferred.
What remains uncertain
- No iron-salt-specific human liothyronine pharmacokinetic result was verified. Four-to-five-hour guidance is not a measured minimum interval across all preparations.
Factors that may matter: exact supplement preparation and dose; oral versus nonoral medication route; other formula ingredients; patient thyroid status.
Read the supporting source summaries
Source 1: regulatory product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed oral liothyronine sodium tablets.
T3 dose depends on food, other medicines, clinical response and laboratory results. Table 1 explicitly names resins and bile-acid sequestrants, but does not name the mineral, fiber, soy or botanical pairs evaluated here.
How this applies: Confirms exact liothyronine active moiety, not levothyroxine. Supports monitored individualized treatment; mineral and botanical conclusions require other sources. Exact package scope: Oral liothyronine sodium tablets with oral iron preparations. The intestinal absorption precaution does not apply to an iron infusion in the same way.
Absence of a named interaction is not evidence of absence. The four-hour resin instruction cannot automatically be transferred to minerals or fiber.
Source 2: institutional patient medication monograph
myhealth.alberta.ca · Source check Sep 10, 2026
Population: People using oral liothyronine.
Monograph specifically names these products as potentially reducing liothyronine absorption and recommends at least four hours before or after.
How this applies: Exact medication is named. Guidance supports a cautious scheduling recommendation for listed oral products, not a measured clinical effect across every mineral preparation. Exact package scope: Oral liothyronine sodium tablets with oral iron preparations. The intestinal absorption precaution does not apply to an iron infusion in the same way.
Secondary patient guidance provides no underlying liothyronine-only trial, salt-specific effect size, threshold dose or validated four-hour comparison.
Source 3: institutional clinical guidance
lifeblood.com.au · Source check Sep 10, 2026
Population: Patients receiving oral iron for iron deficiency.
Advises spacing oral iron and thyroid hormones by four to five hours.
How this applies: Supports a liothyronine-specific scheduling precaution for oral iron, not injectable iron. Exact package scope: Oral liothyronine sodium tablets with oral iron preparations. The intestinal absorption precaution does not apply to an iron infusion in the same way.
Clinical guidance does not report a liothyronine-only pharmacokinetic trial or establish equal effect for all iron salts.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Narrows both imported statements to oral iron and guidance-based spacing, with four hours as the minimum shared by the inspected clinical references. | |
| Research summary published |
Article revision: 3f9f06462a68707b
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.