Lithium and Methimazole interaction
Lithium and Methimazole: the Lithium prescribing label describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Lithium (Lithium Carbonate) label · effective 2026-06-04
• Hypothyroidism and Hyperthyroidism: Monitor thyroid function regularly ( 5.7 ).
Where hypothyroidism exists, careful monitoring of thyroid function during lithium stabilization and maintenance allows for correction of changing thyroid parameters, if any.
Monitor thyroid function before the initiation of treatment, at three months and every six to twelve months while treatment is ongoing.
If serum thyroid tests warrant concern, monitoring should occur more frequently.
Hypothyroidism or Hyperthyroidism Lithium is concentrated within the thyroid and can inhibit thyroid synthesis and release which can lead to hypothyroidism.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.