Ashwagandha and the Thyroid: Hyperthyroidism, Thyroid Medicines and Test Results

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

1. Pilot trial, 8 weeks

   Small, single-center pilot; promising but limited

   TSH, T3 and T4 improved significantly compared with placebo [3]

   Who and what: 50 adults with mildly raised TSH (subclinical hypothyroidism), root extract 600 mg daily versus placebo [3]

2. Endocrinology review, 2022

   Expert review

   Ashwagandha root extract has little to no evidence of any impact on thyroid disorders [4]

   Who and what: Dietary and alternative approaches to thyroid disease [4]

3. Safety trial, 8 weeks

   Small; healthy people only

   No untoward effects in treated volunteers [5]

   Who and what: 80 healthy volunteers, 300 mg twice daily versus placebo; thyroid function was among the primary safety outcomes [5]

4. Review of healthy-adult trials

   Healthy adults, not thyroid patients

   Endocrine biomarkers stayed within normal clinical ranges [6]

   Who and what: Standardized root extracts [6]

5. Trial in bipolar disorder

   Very small groups (3 treated, 7 on placebo among those abnormal) [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]

   Who and what: 60 patients; thyroid tests done for safety [7]

6. Rats with induced hypothyroidism

   Preclinical (animals), not evidence for people

   Improved thyroid hormones in rats [8]

   Who and what: Methanolic extract [8]

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

More: Adaptogens and thyroid conditions, supplements and thyroid medicines, thyroid problems and fatigue, medicine interactions and claims about adaptogens and "hormone balance".