Although there are a number of studies that suggest ashwagandha has thyroid-stimulating effects, the jury is still out on whether this effect is caused by supplement contamination with thyroid hormones, as opposed to ashwagandha itself.[1] There are at least three case reports where people developed thyrotoxicosis (excessively high thyroid hormone levels) from supplementing with ashwagandha.[2] There are also at least four case reports that documented a variable, modest increase in thyroid hormone levels.[3] However, there are no clinical trials testing ashwagandha in people with overt hypothyroidism. In one 8-week randomized controlled trial of 50 patients with subclinical hypothyroidism, taking 300 mg of ashwagandha root extract twice daily increased thyroxine levels by 20% while levels of thyroid-stimulating hormone (TSH) decreased by 17% compared to a starch placebo.[4] However, in another 8-week randomized controlled trial, the same dose and type of ashwagandha root extract did not affect thyroid hormones in euthyroid individuals.[5]
What’s the story with ashwagandha for hypothyroidism?
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•Last Updated: May 16, 2025
Ashwagandha may have thyroid-stimulating effects, as suggested by some studies and case reports, but its efficacy in treating hypothyroidism remains unclear due to potential supplement contamination and a lack of clinical trials specifically for overt hypothyroidism. Some trials indicate that it can increase thyroxine levels in subclinical hypothyroidism, but others show no effect in individuals with normal thyroid function.