The short answer
Possibly. In a small placebo-controlled trial, eight weeks of ashwagandha root extract lowered TSH and raised T3 and T4 in people with subclinical hypothyroidism. Case reports describe thyrotoxicosis, too much thyroid hormone, in people taking ashwagandha, including a woman who had used it for two years for hypothyroidism.
No study has tested ashwagandha together with levothyroxine, so the combined effect is not known. If you take a thyroid medicine, tell your prescribing doctor before you start ashwagandha, and ask whether your thyroid levels should be rechecked.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| Raised T3 and T4, lowered TSH[1] | Not established. Animal data suggest ashwagandha can increase thyroid hormone levels. | May add to levothyroxine; may oppose carbimazole or methimazole | RCT |
| Thyrotoxicosis after use[2][3] | Not established | Too much thyroid hormone | Case report |
No listing is not a clearance. A missing interaction here never means a combination is safe.
The evidence, study by study
Trial in subclinical hypothyroidism, India, 2018 RCT
Fifty adults with TSH between 4.5 and 10 were given ashwagandha root extract (600 mg daily) or placebo for eight weeks. TSH, T3 and T4 all moved towards normal in the ashwagandha group compared with placebo. The trial was small, short and single-centre, and nobody in it was taking levothyroxine.[1]
Case report, the Netherlands, 2005 Case report
A healthy 32-year-old woman developed thyrotoxicosis after increasing her dose of ashwagandha capsules taken for fatigue. Her symptoms and blood tests returned to normal after she stopped. She was taking no other medicines.[2]
Case report, United States, 2022 Case report
A 73-year-old woman who had taken ashwagandha root extract for two years to treat her own hypothyroidism presented with a fast heart rhythm (supraventricular tachycardia), symptoms of hyperthyroidism and a very low TSH. She recovered after stopping the supplement.[3]
What to tell your prescribing doctor
You can read this out, or show them this page:
“I am taking, or planning to take, ashwagandha (name of product, dose) along with my thyroid medicine. Studies suggest ashwagandha can raise thyroid hormone levels. Should my TSH and T4 be checked, and when?”
Withheld until review
Related
Does ashwagandha reduce stress?
One small, positive placebo-controlled trial. Promising, not settled.
FormulationSitopaladi Churna
A classical cough powder, about half sugar by weight. It contains pippali, which can raise phenytoin levels.
Sources
- 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.
- van der Hooft CS, Hoekstra A, Winter A, et al. Thyrotoxicosis following the use of ashwagandha. Ned Tijdschr Geneeskd. 2005;149(47):2637-8. PMID 16355578.
- Kamal HI, Patel K, Brdak A, et al. Ashwagandha as a unique cause of thyrotoxicosis presenting with supraventricular tachycardia. Cureus. 2022;14(3):e23494. PMID 35475098.
Awaiting review by The Good Vaidya Medical Board. Prepared from the sources below and checked against each one.
Published 4 November 2026 · Last updated 4 November 2026
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