Does Levothyroxine Sodium Interact with Methimazole?
CDI records a major classification for Levothyroxine Sodium and Methimazole. The stored summary is: May decrease thyroid hormone secretion, which may result in hypothyroidism when used with levothyroxine. The mechanism involves decreased thyroid hormone secretion. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This record was extracted from drug labeling through openFDA. NIH/NLM RxNorm is used for drug identities. The summary and severity classification are CDI's processed information, not a verbatim source quotation. Product, route, and patient circumstances matter.
Evidence status
A current label comparison is not yet available for this record. The summary and severity are stored CDI information; they have not been independently validated on this page against the exact product label.
Confirm the medicine, formulation, route, and applicable warning with your pharmacist or prescriber. Independent clinical review has not been recorded.
- Stored CDI classification
- Major
- Methimazole Class
- Thyroid Hormone Synthesis Inhibitor
- Management
- Confirm exact products with your pharmacist
- Data Source
- U.S. FDA via OpenFDA
Recorded Mechanism
Decreased thyroid hormone secretion
What To Tell Your Doctor or Pharmacist
If you are taking Levothyroxine Sodium and your doctor is considering prescribing Methimazole (or vice versa), make sure to:
- Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
- Ask whether the benefits of combining these medications outweigh the risks for your specific situation
- Ask what symptoms to watch for that would indicate the interaction is causing problems
- Ask how frequently you should be monitored while these are co-prescribed
- Ask whether any dosage adjustments are needed
- Never stop or change either medication without first consulting your healthcare provider