Does Dexamethasone Interact With Levothyroxine?
Glucocorticoids (e.g., Dexamethasone ≥ 4 mg/day) Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels.
Severity: Moderate
Severity basis: drug interactions section (keywords: may decrease). Combining Dexamethasone (Systemic corticosteroid) and Levothyroxine (Thyroid hormone) is classified as a moderate interaction.
What to Do
Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.
How This Interaction Works
Interactions like this one can happen when two medicines have overlapping effects, or when one changes how the other is absorbed, broken down, or cleared from the body. Dexamethasone is a systemic corticosteroid and Levothyroxine is a thyroid hormone; together they are documented as a moderate interaction. How much this matters depends on your dose, your other medications, and your overall health.
If You Take Both Medications
If you have been prescribed both Dexamethasone and Levothyroxine, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
From the FDA Label
Glucocorticoids (e.g., Dexamethasone ≥ 4 mg/day) Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels.
Source: FDA structured product labeling (set_id 008de8fd-150f-4022-8ccb-c8bfa94875c7).
Check these against your full medication list in our free Interaction Checker
Frequently Asked Questions
Can you take Dexamethasone and Levothyroxine together?
Dexamethasone and Levothyroxine have a documented moderate interaction. Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.
How serious is the Dexamethasone and Levothyroxine interaction?
It is classified as a moderate interaction, based on the FDA label's drug interactions section (keywords: may decrease). A moderate interaction can be clinically meaningful and usually calls for monitoring or a dose adjustment.
What should I do if I'm taking both Dexamethasone and Levothyroxine?
If you have been prescribed both Dexamethasone and Levothyroxine, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
This information is educational — not medical advice.
This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.
Other Dexamethasone Interactions
- Dexamethasone + Carbamazepine(moderate)
- Dexamethasone + Hydrocortisone(moderate)
- Dexamethasone + Itraconazole(moderate)
- Dexamethasone + Liothyronine(moderate)
- Dexamethasone + Aspirin(minor)
- Dexamethasone + Cyclosporine(minor)
- Dexamethasone + Indomethacin(minor)
- Dexamethasone + Ketoconazole(minor)
- Dexamethasone + Phenytoin(minor)
- Dexamethasone + Rifampin(minor)
- Dexamethasone + Warfarin(minor)
Other Levothyroxine Interactions
- Levothyroxine + Amitriptyline(moderate)
- Levothyroxine + Carbamazepine(moderate)
- Levothyroxine + Alendronate(minor)
- Levothyroxine + Amiodarone(minor)
- Levothyroxine + Aspirin(minor)
- Levothyroxine + Ferrous Sulfate(minor)
- Levothyroxine + Furosemide(minor)
- Levothyroxine + Liothyronine(minor)
- Levothyroxine + Nifedipine(minor)
- Levothyroxine + Phenytoin(minor)
- Levothyroxine + Propranolol(minor)
- Levothyroxine + Rifampin(minor)
- Levothyroxine + Semaglutide(minor)
- Levothyroxine + Sertraline(minor)
- Levothyroxine + Sucralfate(minor)