Ashwagandha and the Thyroid: Hyperthyroidism, Thyroid Medicines and Test Results
What trials, case reports and NIH say about ashwagandha and thyroid hormone levels, hyperthyroidism, thyroid medicines and blood test results, and why people with thyroid disease should ask first.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Safety first. NCCIH says ashwagandha is not recommended for people with thyroid disorders and that it might interact with thyroid hormone medicines. [1] If you take a thyroid medicine or have a thyroid condition, ask the prescriber or pharmacist before using it. Never stop or change a prescribed thyroid medicine on your own. If you develop a fast heartbeat, weight loss or night fevers while using ashwagandha, as described in the case reports below, contact a clinician; call 911 (US) if you feel seriously unwell.
What the sources found
| Source | Who and what | What it found | Strength |
|---|---|---|---|
| Pilot trial, 8 weeks | 50 adults with mildly raised TSH (subclinical hypothyroidism), root extract 600 mg daily versus placebo [3] | TSH, T3 and T4 improved significantly compared with placebo [3] | Small, single-center pilot; promising but limited |
| Endocrinology review, 2022 | Dietary and alternative approaches to thyroid disease [4] | Ashwagandha root extract has little to no evidence of any impact on thyroid disorders [4] | Expert review |
| Safety trial, 8 weeks | 80 healthy volunteers, 300 mg twice daily versus placebo; thyroid function was among the primary safety outcomes [5] | No untoward effects in treated volunteers [5] | Small; healthy people only |
| Review of healthy-adult trials | Standardized root extracts [6] | Endocrine biomarkers stayed within normal clinical ranges [6] | Healthy adults, not thyroid patients |
| Trial in bipolar disorder | 60 patients; thyroid tests done for safety [7] | Ten patients had abnormal results at some point, and the authors saw T4 rises in three treated patients, suggesting ashwagandha may increase thyroxine [7] | Very small groups (3 treated, 7 on placebo among those abnormal) [7] |
| Rats with induced hypothyroidism | Methanolic extract [8] | Improved thyroid hormones in rats [8] | Preclinical (animals), not evidence for people |
Case reports of overactive thyroid
- A healthy 32-year-old woman developed thyrotoxicosis on ashwagandha capsules taken for chronic fatigue, after increasing the amount; symptoms and lab values normalized after stopping. [9]
- A 73-year-old woman who had used a root extract for two years as self-treatment for hypothyroidism presented with a fast heart rhythm (supraventricular tachycardia) and low TSH; she recovered after stopping. [10]
- A previously healthy 47-year-old man had thyrotoxicosis from painless thyroiditis two months before his hospital visit; his symptoms and thyroid markers improved after he stopped. [11]
Case reports cannot prove cause and effect, and the reporting authors say the mechanism is unclear. [10] They do show that the reaction is possible. A 2026 review also lists people with thyroid disorders among groups at significant risk. [12]
Thyroid medicines and test results
- Interactions: NCCIH lists thyroid hormone medicines among those ashwagandha might interact with. [1] The sources we read do not describe how or by how much, so we cannot give a figure.
- Test results: The changes described above are changes in thyroid hormones or TSH themselves. Proper evidence not found for ashwagandha interfering with the laboratory test method, as some other supplements do. We searched PubMed for ashwagandha with thyroid, levothyroxine and test interference. For that kind of problem, see biotin and lab-test interference.
- Practical point: tell the prescriber and the lab team about any supplement before thyroid tests, and ask whether tests should be repeated. The authors of one small trial said vigilance about hyperthyroidism may be warranted. [7]
What this page cannot tell you
It cannot say whether ashwagandha is safe for a given person with thyroid disease, or whether it helps hypothyroidism. NCCIH advises against it for thyroid disorders. [1]More: Adaptogens and thyroid conditions, supplements and thyroid medicines, thyroid problems and fatigue, medicine interactions and claims about adaptogens and "hormone balance".
Frequently asked questions
Can ashwagandha cause an overactive thyroid?
Case reports describe thyrotoxicosis after use that resolved after stopping, and a small trial saw T4 rises. [9][10][11][7]
Does ashwagandha treat hypothyroidism?
One pilot trial in subclinical hypothyroidism reported improved TSH, T3 and T4; an endocrinology review found little to no evidence of impact. [3][4] Do not replace a prescribed thyroid medicine with it; ask the prescriber.
Does it interact with levothyroxine or other thyroid medicines?
NCCIH says it might interact with thyroid hormone medicines. [1] Ask the prescriber or pharmacist.
Will it change my thyroid blood tests?
Trials and case reports show real changes in TSH, T3 or T4 in some people, while trials in healthy adults found values in normal ranges. [3][10][6] Tell your clinician you use it.
Who should avoid it?
NCCIH says it is not recommended for people with thyroid disorders, in pregnancy, or before surgery. [1]
References
- NIH National Center for Complementary and Integrative Health, page last updated March 2023: Ashwagandha: Usefulness and Safety. Read 2026-10-23.
- GBIF species match, queried 2026-10-23: GBIF Backbone Taxonomy: Withania somnifera. Read 2026-10-23.
- Journal of Alternative and Complementary Medicine, 2018: Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. Read 2026-10-23.
- Journal of Clinical Endocrinology & Metabolism, 2022: Thyroid, Diet, and Alternative Approaches. Read 2026-10-23.
- Complementary Therapies in Medicine, 2021: Safety of Ashwagandha Root Extract: A Randomized, Placebo-Controlled, study in Healthy Volunteers. Read 2026-10-23.
- Pharmaceuticals (Basel), 2026: Back to the Roots: Safety and Tolerability of Standardised Ashwagandha (Withania somnifera) Root Extract in Healthy Adults - A Systematic Review of Biomarkers and Adverse Events. Read 2026-10-23.
- Journal of Ayurveda and Integrative Medicine, 2014: Subtle changes in thyroid indices during a placebo-controlled study of an extract of Withania somnifera in persons with bipolar disorder. Read 2026-10-23.
- Molecular Biology Reports, 2019: Role of ashwagandha methanolic extract in the regulation of thyroid profile in hypothyroidism modeled rats. Read 2026-10-23.
- Nederlands Tijdschrift voor Geneeskunde, 2005: Thyrotoxicosis following the use of ashwagandha (Nederlands Tijdschrift voor Geneeskunde). Read 2026-10-23.
- Cureus, 2022: Ashwagandha as a Unique Cause of Thyrotoxicosis Presenting With Supraventricular Tachycardia. Read 2026-10-23.
- Cureus, 2024: Painless Thyroiditis by Withania somnifera (Ashwagandha). Read 2026-10-23.
- Phytotherapy Research, 2026: Evaluating the Safety of Ashwagandha as a Food Additive: A Focus on Reproductive, Thyroid, and Immune System Effects. Read 2026-10-23.