A summary of published research, not medical advice. See the Disclaimer.
Studies: every indexed trial and review on this topic, scored
Ashwagandha (Withania somnifera) is a shrub used in Ayurvedic medicine. Its root or leaf extract is sold as a supplement.
Best-supported effect: Lower self-rated stress and anxiety in adults with high stress. May help (weak evidence).
Most-cited weak claim: Higher testosterone in men. Unknown (very weak evidence).
How we grade evidence · Last reviewed: October 2026
What you need to know
No effect of ashwagandha has more than weak evidence. In adults with self-reported high stress, trials found lower self-rated stress and anxiety, and other trials found slightly better sleep quality and a small rise in muscle strength, all with weak evidence. Whether it raises testosterone in men is unknown. Case reports describe liver injury with jaundice, including liver failure and death in 3 people with pre-existing chronic liver disease, and overactive thyroid. A safety review names pregnant women, people with thyroid disorders and people with liver or kidney dysfunction as groups at higher risk. Trials used standardized extracts, mostly from the root, at 240 to 600 mg a day for 8 weeks to 60 days.
No effect reaches "Probably helps" yet.
| Claim | Verdict | What was measured | Studied in |
|---|---|---|---|
| Lower self-rated stress and anxiety | May help (weak evidence) Pooled analysis of 12 trials with 1,002 people, size of the effect varied widely |
Self-reported | Adults with self-reported high stress |
| Better sleep quality | May help a little (weak evidence) Review that pooled 5 trials with 400 people, small overall improvement |
Self-reported | Adults with and without insomnia |
| Lowers cortisol | May help (weak evidence) Review of 9 trials found lower cortisol, designs and doses differed |
Lab marker | Stressed adults |
| Increases muscle strength | May help a little (weak evidence) Small trials in narrow groups, measuring different outcomes |
Measured | Healthy adults, mostly young men starting resistance training |
| Raises testosterone | Unknown (very weak evidence) A few small trials in narrow groups, results mixed |
Lab marker | Men, mostly young and healthy, some doing resistance training |
A meta-analysis of 12 randomized controlled trials with 1,002 participants found that ashwagandha lowered stress and anxiety scores compared with placebo [1]. In one trial, 64 adults with chronic stress received root extract for 60 days, and their stress questionnaire scores fell more than with placebo [2]. A 60-day trial in 60 stressed adults found lower anxiety ratings on one scale with a different extract; a second stress-and-anxiety scale did not reach significance [3]. May help (weak evidence): effect sizes varied widely between trials, and the meta-analysis rated the certainty of its own evidence as low [1].
A meta-analysis of five RCTs with 400 participants found a small improvement in overall sleep compared with placebo [4]. The effect was larger in people with insomnia, at doses of at least 600 mg/day, and in trials lasting 8 weeks or more [4]. May help a little (weak evidence): the trials were few and small, and the effect depended on who was studied.
The claim is about cortisol itself, so the lab-marker rule does not apply. May help (weak evidence): the trials were small and varied. A systematic review of 9 trials concluded that ashwagandha lowered cortisol, though the trials differed in design, dose and duration [5]. In one 60-day trial, serum cortisol fell more with the extract than with placebo [2], and a second 60-day trial found the same for morning cortisol [3].
The strength claim comes mainly from small trials in young men. One 8-week trial of 57 men with little resistance-training experience found larger gains in bench press and leg extension strength, and in muscle size, than with placebo [6]. A Bayesian meta-analysis of 12 trials in healthy men and women found ashwagandha outperformed placebo on physical performance measures [7]. May help a little (weak evidence): the trials were small, in narrow groups, and measured different outcomes.
The testosterone claim rests on a few small trials. A systematic review of herbs and testosterone found positive effects with ashwagandha root and root-and-leaf extracts, but noted small samples, varied extracts and doses, and mostly young, healthy participants [8]. The 8-week strength trial also reported a larger rise in testosterone than with placebo [6]. In a 60-day stress trial, testosterone rose in men but not significantly more than with placebo [3]. Testosterone is a blood marker, and no trial cited here measured fertility, libido or body composition as the main outcome. Unknown (very weak evidence): a few small trials in narrow groups, with mixed results.
The trials cited here lasted at most about 4 months, and none tested whether these effects last longer [5].
Shown in humans
Shown only in animals or cells
Theory only
| Side effect | Verdict | How often vs placebo | Source | Studied in |
|---|---|---|---|---|
| Mild adverse events in short trials | May not increase it (weak evidence) Four short trials, rates similar or none, one 4% vs 12% |
Comparable in both groups [2]; 4% vs 12% [11]; none in either group [3][12] | [2][3][11][12] | Adults; Healthy Volunteers |
| Serious adverse events | May not increase it (weak evidence) None reported, but short trials not designed for rare harms |
None reported | [2][4] | Adults |
| Liver injury (cholestatic or mixed, with jaundice) | Unknown (very weak evidence) Reports of single patients only, no controlled comparison, no rate available |
Case reports only | [9][10] | |
| Overactive thyroid (thyrotoxicosis) | Unknown (very weak evidence) Only three reports of single patients, no rate available |
Case reports only | [14][15][16] | |
| Changes in thyroid hormone levels | May happen (weak evidence) Shifted in people with abnormal thyroid values, unchanged in healthy adults |
T3 and T4 up, TSH down vs placebo in 50 people with mildly underactive thyroid [11]; T4 rose in 3 of 3 treated vs fell in 6 of 7 on placebo among people with abnormal values [13]; no change in 80 healthy adults [12] | [11][12][13] | People with abnormal thyroid values; Healthy adults |
The trials were short and not designed to detect rare harms; the sleep meta-analysis noted that data on serious adverse effects are limited [4]. In the liver case series, jaundice began after 2 to 12 weeks of use and liver tests returned to normal within 1 to 5 months in four of five patients [9]; in a series of 8 patients from India, 3 with pre-existing liver disease developed liver failure and died [10]. Case reports cannot give a rate, and with no controlled comparison the liver harm is graded Very limited.
This lists what studies and labels report. A pharmacist or prescriber can say whether it applies to a specific person.
This lists what studies and labels report. A pharmacist or prescriber can say whether it applies to a specific person.
| Combined with | What happened | Verdict | Source | Studied in |
|---|---|---|---|---|
| Antidepressants (sertraline, escitalopram, paroxetine, reboxetine) | A chart review of adverse event reports linked combined use with diarrhoea, nausea and vomiting, muscle pain, restless legs, eye pain with raised eye pressure, and testicular pain with ejaculation problems | Unknown (very weak evidence) One look back through medical charts at reports of harmful events |
[23] | |
| Drugs broken down by the liver enzymes CYP3A4 or CYP1A2 | Extracts increased CYP3A4 and CYP1A2 activity in lab cell tests, and a root extract altered CYP3A4 in human liver cells; no human study measured drug levels | Unknown (very weak evidence) Lab cell tests only, no human drug level data |
[24][25] | |
| Drugs broken down by seven common CYP liver enzymes | Four root and leaf extracts did not block any of the seven enzymes in a lab test | Unknown (very weak evidence) Single lab test, four extracts blocked none of the enzymes |
[26] | |
| Pentobarbital (a barbiturate sedative) | Extracts lengthened pentobarbital-induced sleep in mice | Unknown (very weak evidence) Only mouse studies, extracts lengthened sleep caused by a sedative |
[18][19] | Mice |
No interaction study with thyroid medication, other sedatives or immunosuppressants was found.
These are the amounts used in the studies. They are not recommendations.
Trials used standardized extracts, mostly from the root, at 240–600 mg/day for 8 weeks to 60 days, taken once or twice daily [2][3][6]. In the sleep meta-analysis, effects were larger at 600 mg/day or more and with 8 weeks or more of use [4]. Extracts and doses differed between trials, so results from one extract may not apply to another [8].