The short answer
Possibly. In a small placebo-controlled trial in India, 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 to treat her own 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.
Levothyroxine is sold in India as Thyronorm and Eltroxin. Carbimazole is sold as Neo-Mercazole, and methimazole as Methimez.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| Raised T3 and T4, lowered TSH[1][6][7] | Not established | May add to levothyroxine; may work against carbimazole or methimazole | RCT |
| Thyrotoxicosis or thyroiditis after use[2][3][4] | Not established | Too much thyroid hormone | Case report |
| Liver injury from ashwagandha products[5] | Not established | Herb safety context, not an interaction | 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 aged 18 to 50 with TSH between 4.5 and 10 took ashwagandha root extract (600 mg a day) or a starch placebo for eight weeks at one centre; four dropped out. TSH, T3 and T4 all moved towards normal with ashwagandha compared with placebo. The trial was small and single-centre, and it was not designed to test an interaction with levothyroxine.[1]
Case report, the Netherlands, 2005 Case report
A healthy 32-year-old woman developed thyrotoxicosis after increasing her intake of an ashwagandha extract she was taking for fatigue. It settled after she stopped. She was taking no other remedies or 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 came to hospital with a fast heart rhythm (supraventricular tachycardia) and a suppressed TSH. Her symptoms and blood tests improved after she stopped the supplement. The report does not confirm that she was also on levothyroxine.[3]
Case report, Japan, 2024 Case report
A previously healthy 47-year-old man developed painless thyroiditis, an inflamed thyroid that leaks hormone, after two months of ashwagandha. His symptoms and thyroid tests improved once he stopped.[4]
Case series, India, 2023 Case report
Liver specialists at several Indian centres described 8 people with liver injury after single-herb ashwagandha products. Five already had chronic liver disease, and three of them developed acute-on-chronic liver failure and died. This is about ashwagandha's own risk to the liver, not about thyroid medicines.[5]
What your doctor may watch for
- TSH and free T4, which your doctor already uses to judge your thyroid dose.[1]
- A racing or irregular heartbeat, which can be a sign of too much thyroid hormone. It was how the 2022 case first showed up.[3]
- Levothyroxine has a narrow therapeutic index, so small changes in thyroid hormone levels can matter.[8]
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, form and how much) 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
Questions people ask
Can I take ashwagandha if I have hypothyroidism?
Nobody has studied it alongside levothyroxine. Because ashwagandha can raise thyroid hormone levels by itself, the question is one for your prescribing doctor, who may want to recheck your TSH after you start.[1]
Does ashwagandha cure hypothyroidism?
No. One small trial in people with mildly raised TSH found that their thyroid tests moved towards normal over eight weeks. That is not a cure, and the study does not show whether ashwagandha can replace prescribed thyroid treatment.[1]
Related
Does ashwagandha change thyroid blood tests?
In one small trial of people with a mildly raised TSH, eight weeks of ashwagandha root extract moved thyroid tests towards normal.
ConditionUnderactive thyroid (hypothyroidism): what Ayurveda offers
One small trial found ashwagandha improved mildly raised TSH. No trial we found tested Ayurveda in place of levothyroxine. Do not stop it.
FormulationAshwagandharishta
A fermented ashwagandha tonic with alcohol and a lot of honey. One trial in depression compared it, with Brahmi vati, against escitalopram.
InteractionBrahmi and thyroid medicines
Not tested in people. In mice, a brahmi extract raised the thyroid hormone T4 by 41%, which could matter if you take a thyroid medicine.
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, de Smet PA, Stricker BH. Thyrotoxicosis following the use of ashwagandha. Ned Tijdschr Geneeskd. 2005;149(47):2637-2638. PMID 16355578.
- Kamal HI, Patel K, Brdak A, Heffernan J, Ahmad N. Ashwagandha as a unique cause of thyrotoxicosis presenting with supraventricular tachycardia. Cureus. 2022;14(3):e23494. PMID 35475098.
- Hayashi M, Hamada H, Azuma SI, Hayashi K. Painless thyroiditis by Withania somnifera (ashwagandha). Cureus. 2024;16(3):e55352. PMID 38559552.
- Philips CA, Valsan A, Theruvath AH, Ravindran R, Oommen TT, Rajesh S, Bishnu S, Augustine P; Liver Research Club India. Ashwagandha-induced liver injury: a case series from India and literature review. Hepatol Commun. 2023;7(10):e0270. PMID 37756041.
- Memorial Sloan Kettering Cancer Center. About Herbs: Ashwagandha.
- National Center for Complementary and Integrative Health (US). Ashwagandha.
- Levothyroxine sodium tablets, US prescribing information (DailyMed).
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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