NutriStack
Ashwagandha and Methimazole, a conflict.
Ashwagandha may increase thyroid hormone levels or trigger thyrotoxicosis in susceptible people. That can oppose the purpose of methimazole, which is used to bring excessive thyroid hormone production under control. The evidence is limited, but the clinical direction is concerning for people being treated for hyperthyroidism.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Ashwagandha and Methimazole
- Pair type
- Conflict
- Evidence (highest tier)
- Emerging
- Source citations
- 2 sources
- Stack Score effect
- −10 to your Stack Score (per scored conflict row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Conflict · Emerging evidence
Conflict
What is happening. Ashwagandha may increase thyroid hormone levels or trigger thyrotoxicosis in susceptible people. That can oppose the purpose of methimazole, which is used to bring excessive thyroid hormone production under control. The evidence is limited, but the clinical direction is concerning for people being treated for hyperthyroidism.
Mechanism. Ashwagandha has been associated with higher thyroid hormone indices and case reports of thyrotoxicosis. This may pharmacodynamically counter methimazole's antithyroid effect even though it is not known to alter methimazole metabolism.
Recommendation. Avoid ashwagandha while taking methimazole unless your thyroid clinician explicitly approves it. If you have already started it, report palpitations, tremor, heat intolerance, anxiety, or worsening thyroid labs promptly.
Sources (2)
- van der Hooft CS, Hoekstra A, Winter A, de Smet PA. Thyrotoxicosis following the use of ashwagandha. Ned Tijdschr Geneeskd. 2005;149(47):2637-2638. PMID 16355578
- Sharma AK, Basu I, Singh S. Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. J Altern Complement Med. 2018;24(3):243-248. PMID 28829155
Stack Score
How this pair moves the number.
Effect on the composite score
If both Ashwagandha and Methimazole are in the same stack, this pair applies −10 to your Stack Score (per scored conflict row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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