What does the research show about ashwagandha?

Ashwagandha

Pooled trials report lower stress, anxiety, sleep scores and cortisol, and higher testosterone in men, with high heterogeneity and many small, branded trials. Endurance gains were modest and strength gains less certain. Case series describe cholestatic liver injury, including three deaths in people with existing liver disease. A 1,002-person trial found no serious adverse events over 8 weeks.

Add to Bio HackChecked 2026-11-13

Status: Dietary supplement in the US. Germany's Federal Institute for Risk Assessment advised in 2024 against use by children, pregnant and breastfeeding women and people with liver disease.
Also called: Withania somnifera, winter cherry, Indian ginseng, KSM-66, Sensoril, Shoden, withanolides
Taken for: stress, anxiety, depression, sleep, cortisol, testosterone, strength, VO2 max, recovery, libido, thyroid

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help7

StrongShown to improve overall sleep in adults, more in people with insomnia, at 600 mg a day or more, and after 8 weeks or longer.
StrongShown to lower cortisol by about 1.2 µg/dL against placebo in adults, though perceived stress did not change in the same review.
StrongShown to raise testosterone in men, by about 57 ng/dL in one review, with no change in women. Rises stayed within physiological ranges.
ModerateShown to raise VO2 max and aerobic endurance in healthy adults and athletes, though results varied widely across small trials.
ModerateShown to raise muscle strength in physically active people but not in untrained people. Results leaned on single trials and certainty was low.
ModerateShown to lower depression scores in people with mental disorders, mostly anxiety disorders, though a second statistical model did not confirm the effect.
LimitedOne small trial found 600 mg a day raised recovery and sleep quality scores in 30 female footballers over 28 days.

Reported risks3

ModerateCase reports: people developed jaundice and liver injury after 2 to 12 weeks, most recovering within months. Three with existing liver disease died.How often is not known
ModerateGermany's BfR advises children, pregnant and breastfeeding women, and people with liver disease not to take ashwagandha, citing case reports of liver damage.How often is not known
LimitedLimited evidence: animal studies showed no clear reproductive toxicity, and no controlled human pregnancy study exists. Germany's BfR advises pregnant women not to take it.How often is not known

What people take it for, and what was found

Shown to help7

Strong

Sleep

Shown to improve overall sleep in adults, more in people with insomnia, at 600 mg a day or more, and after 8 weeks or longer.

The numbers and sources

Effect: In 5 RCTs (400 participants), ashwagandha extract improved overall sleep (SMD -0.59, 95% CI -0.75 to -0.42, I² 62%). Effects were larger in adults diagnosed with insomnia, at 600 mg a day or more, and at 8 weeks or longer. Mental alertness on rising and anxiety improved, and quality of life did not change [5]. In people with mental disorders, sleep quality improved (SMD -1.35, 95% CI -1.79 to -0.91) [2].
Population: Adults 18 and older in 5 RCTs [5]. People with mental disorders [2].
Sources: [5], [2]
Caveats: Five trials in [5], whose authors write that data on serious adverse effects are limited. The mental disorders review describes a role in insomnia as still to be clarified [2].

Strong

Cortisol

Shown to lower cortisol by about 1.2 µg/dL against placebo in adults, though perceived stress did not change in the same review.

The numbers and sources

Effect: Across 7 trials, cortisol fell 1.16 µg/dL (95% CI -1.64 to -0.69) against placebo [4]. Across 23 placebo-controlled trials, cortisol fell (SMD -1.18, p < 0.04), with a possible dose-response by withanolide content [6]. A review of 23 trials of standardized root extract in healthy adults reported consistent cortisol reductions [7].
Population: Adults in RCTs of 2 weeks or more at 250 mg a day or more [4]. 1,706 adults in 23 RCTs [6]. 2,317 healthy adults [7].
Sources: [4], [6], [7]
Caveats: In the same review, cortisol fell while perceived stress did not change [4]. Cortisol is a lab marker, not a symptom. Two authors of [7] reported employment by companies, and two reported honoraria from supplement companies.

Strong

Testosterone

Shown to raise testosterone in men, by about 57 ng/dL in one review, with no change in women. Rises stayed within physiological ranges.

The numbers and sources

Effect: Across 20 trials of cognitive and physical outcomes, testosterone rose (SMD 0.33, 95% CI 0.13 to 0.54, I² 20.8%) [8]. A hormone meta-analysis found testosterone rose by 57.43 ng/dL in men but not in women (5.09 ng/dL), and estradiol did not change [6]. In 57 overweight men aged 40 to 70 with mild fatigue, 8 weeks of an ashwagandha extract was associated with a 14.7% greater rise in salivary testosterone and an 18% greater rise in DHEA-S than placebo. Fatigue, vigor and sexual well-being did not differ between groups [9].
Population: 1,249 participants in 20 RCTs [8]. 1,706 adults in 23 RCTs [6]. 57 men, crossover, 43 completed all 16 weeks [9].
Sources: [8], [6], [9]
Caveats: The 57-man trial tested one branded extract and was funded by its maker, Arjuna Natural Ltd [9]. In healthy adults, testosterone rises stayed within physiological ranges [7].

Moderate

VO2 max and endurance

Shown to raise VO2 max and aerobic endurance in healthy adults and athletes, though results varied widely across small trials.

The numbers and sources

Effect: In 4 RCTs (142 participants), VO2 max rose by a mean 3.00 (95% CI 0.18 to 5.82) with high heterogeneity [10]. A Bayesian meta-analysis of 12 trials reported ashwagandha outperformed placebo on cardiorespiratory fitness [11]. A 2026 three-level meta-analysis of 13 trials found overall exercise performance improved (Hedges' g 0.47, 95% CI 0.25 to 0.69, I² 60%), most consistently for aerobic endurance (g 0.54, 95% CI 0.22 to 0.85) [12].
Population: Healthy adults and athletes [10][11]. 599 participants, mainly young adults or athletes [12].
Sources: [10], [11], [12]
Caveats: The 95% prediction interval for overall performance ran from -0.40 to 1.33, crossing zero [12]. The Bayesian abstract does not report effect sizes [11].

Moderate

Strength

Shown to raise muscle strength in physically active people but not in untrained people. Results leaned on single trials and certainty was low.

The numbers and sources

Effect: A Bayesian meta-analysis reported ashwagandha outperformed placebo on strength and power [11]. Across 20 trials, muscle strength rose (SMD 0.58, 95% CI 0.12 to 1.04, I² 56.9%), in physically active people (SMD 1.03, 95% CI 0.56 to 1.49) but not in untrained or special populations [8]. In 3 resistance-training trials, gains exceeded placebo for 1-RM bench press (SMD 0.60, 95% CI 0.20 to 1.01) and lower-body 1-RM (SMD 0.52, 95% CI 0.19 to 0.86), and body fat did not change [13]. In the three-level analysis, strength effects were positive but uncertain [12].
Population: Healthy men and women [11]. 1,249 participants [8]. 161 healthy adults in structured resistance training [13].
Sources: [11], [8], [13], [12]
Caveats: Under Hartung-Knapp-Sidik-Jonkman adjustment, both resistance-training estimates lost statistical significance, and each depended on one influential trial. Certainty was low [13].

Moderate

Depression symptoms

Shown to lower depression scores in people with mental disorders, mostly anxiety disorders, though a second statistical model did not confirm the effect.

The numbers and sources

Effect: In people with mental disorders, depression symptoms fell (SMD -1.28, 95% CI -2.40 to -0.16) [2]. A 2026 analysis of 22 trials reported lower depression scores (SMD -5.68, 95% CI -8.43 to -2.94) [3].
Population: People with mental disorders, mostly anxiety disorders [2]. Adults in 22 RCTs [3].
Sources: [2], [3]
Caveats: The Bayesian model in [2] confirmed the anxiety effect but not the depression effect.

Limited

Recovery

One small trial found 600 mg a day raised recovery and sleep quality scores in 30 female footballers over 28 days.

The numbers and sources

Effect: A Bayesian meta-analysis reported ashwagandha outperformed placebo on fatigue or recovery [11]. In 30 professional female footballers, 600 mg a day of root extract for 28 days raised total quality recovery scores over placebo (group by time p = 0.026) and improved perceived sleep quality (p = 0.038) [14].
Population: Healthy men and women [11]. 30 female footballers [14].
Sources: [11], [14]
Caveats: One small trial, whose abstract reports p values without effect sizes [14]. The Bayesian abstract does not report effect sizes [11].

Mixed results1

Moderate

Stress and anxiety

Mixed results: most reviews found lower stress and anxiety than placebo in adults, with very high variation, while one review found no change in perceived stress.

The numbers and sources

Effect: Across 12 RCTs (1,002 participants aged 25 to 48), ashwagandha lowered anxiety (SMD -1.55, 95% CI -2.37 to -0.74, I² 93.8%) and stress (SMD -1.75, 95% CI -2.29 to -1.22, I² 83.1%) compared with placebo [1]. In 14 trials in people with mental disorders, mostly anxiety disorders, anxiety fell (outlier-corrected SMD -1.13, 95% CI -1.65 to -0.60) and so did stress (SMD -0.95, 95% CI -1.46 to -0.43) [2]. A 2026 analysis of 22 trials reported lower stress (SMD -5.88, 95% CI -8.15 to -3.60) and anxiety (SMD -6.87, 95% CI -8.77 to -4.97), with stress falling further as dose rose [3]. A 2025 analysis of 6 trials found no change in Perceived Stress Scale scores (SMD -0.355, 95% CI -1.188 to 0.47) [4].
Population: Adults in 12 RCTs [1]. 360 people with mental disorders on ashwagandha and 353 controls [2]. Adults in 22 RCTs [3]. 488 participants in 7 cortisol and 6 stress trials [4].
Sources: [1], [2], [3], [4]
Caveats: Certainty was rated low for both outcomes in [1], and heterogeneity was very high. The mental disorders review was limited by few studies, substantial heterogeneity and outliers [2]. The effect sizes in [3] are several times those in the other reviews. The abstracts do not report funding of the included trials.

Not shown to help1

Moderate

Thyroid hormones

Not shown to change TSH or T3 in adults across 23 trials. T4 rose slightly, by 0.61 µg/dL.

The numbers and sources

Effect: Across 23 placebo-controlled trials, TSH and T3 did not change, and T4 rose by 0.61 µg/dL (p = 0.02) [6].
Population: 1,706 adults [6].
Sources: [6]
Caveats: The authors note heterogeneity and limited data on some endpoints [6].

Doses studied

Sleep effects were larger at 600 mg a day or more for 8 weeks or longer [5]. The stress meta-analysis modeled an effect on stress at 300 to 600 mg a day [1]. The testosterone trial gave an extract delivering 21 mg of withanolide glycosides a day [9]. In exercise trials, 500 to 600 mg a day was the extract dose range with the most evidence [12]. Root extract trials in healthy adults used 125 to 600 mg a day, from a single dose to 180 days [7]. Liver injury cases include 450 mg capsules taken once to three times a day [15].

Risks

Reported risks2

ModerateHow often is not known

Liver injury

Case reports: people developed jaundice and liver injury after 2 to 12 weeks, most recovering within months. Three with existing liver disease died.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: Five cases from Iceland and the US Drug-Induced Liver Injury Network developed jaundice after 2 to 12 weeks, with cholestatic or mixed injury and itching lasting 5 to 20 weeks. None had liver failure, and liver tests normalized in 1 to 5 months [16]. In India, 8 patients had liver injury from single-ingredient ashwagandha. Three with existing chronic liver disease presented with acute-on-chronic liver failure and all three died. Chemical analysis found no adulteration [17]. Two further Serbian cases were rated probable by the updated RUCAM, and a review of published cases notes one liver transplant [15].
Population: Case series and case reports [16][17][15].
Sources: [16], [17], [15], [18], [7]
Caveats: Case reports cannot give a rate. In one Icelandic case, rhodiola was a possible co-cause [16]. In an 8-week trial of 1,002 adults, liver tests did not differ from placebo [18], and a review of 23 root extract trials found liver markers within normal ranges [7].

ModerateHow often is not known

German regulator advice

Germany's BfR advises children, pregnant and breastfeeding women, and people with liver disease not to take ashwagandha, citing case reports of liver damage.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In September 2024 Germany's Federal Institute for Risk Assessment (BfR) advised children, pregnant and breastfeeding women, and people with current or past liver disease not to take ashwagandha preparations, and advised restraint for others. It cited case reports of liver damage including acute liver failure, possible effects on cortisol, blood sugar, thyroid and sex hormones, and possible interactions with antidiabetic, blood pressure and immunosuppressive drugs. It found that no guidance value for a harmless intake could be derived [19].
Population: German consumers [19].
Sources: [19]
Caveats: The BfR notes that human trials did not systematically record adverse effects. It names risk reassessments by Denmark's DTU, the Dutch RIVM, France's ANSES and Australia's TGA [19].

Mixed results1

LimitedHow often is not known

Pregnancy and reproductive toxicity

Limited evidence: animal studies showed no clear reproductive toxicity, and no controlled human pregnancy study exists. Germany's BfR advises pregnant women not to take it.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: A 2025 systematic and ethnobotanical review traced claims of abortifacient effects to historical reports with citation distortion and no primary-source validation. Animal studies showed no significant reproductive toxicity at doses relevant to human use, and the review judged evidence of teratogenic or abortifacient activity inconclusive [20].
Population: Animal toxicology studies, human clinical studies and historical texts [20].
Sources: [20]
Caveats: The review describes no controlled study of pregnancy outcomes in humans. The BfR advised pregnant and breastfeeding women not to take ashwagandha preparations [19].

Checked, no increase found1

Moderate

Adverse events in trials

Adverse events were about as common on ashwagandha as on placebo in trials up to 180 days, 5.6% against 9.2% in the largest.

The numbers and sources

How common: Common: between 1 in 100 and 1 in 10 people.
Effect: The BfR lists acute effects reported with ashwagandha, including nausea, vomiting, diarrhea, drowsiness, headache, dizziness and skin rash, and states that trials did not systematically record unwanted effects [19]. In a 2026 trial in 1,002 adults with stress and anxiety, 600 mg a day of root extract for 8 weeks produced no serious adverse events. Adverse events occurred in 5.6% on extract and 9.2% on placebo, and liver, kidney and blood tests did not differ [18]. A review of 23 trials of standardized root extract found no serious adverse events attributed to it, and mild gastrointestinal discomfort, headache and drowsiness in both groups [7]. The sleep meta-analysis reported no serious side effects in 5 trials [5].
Population: 1,002 adults aged 18 to 65 [18]. 2,317 healthy adults [7]. Trial participants and case reports [5][19].
Sources: [19], [18], [7], [5]
Caveats: Trials ran 180 days or less, so longer-term effects were not measured [7]. The root extract review covered single-ingredient root extracts in healthy adults only, and two of its authors reported employment by companies [7].

Claims tested and not found

That ashwagandha improves fatigue and sexual well-being in older men. In the testosterone trial, fatigue, vigor and sexual well-being did not differ from placebo [9].

Sources

Akhgarjand C, Asoudeh F, Bagheri A, et al. Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials. Phytotherapy Research. 2022. https://doi.org/10.1002/ptr.7598
Marchi M, Grenzi P, Travascio A, et al. The effect of Withania somnifera (Ashwagandha) on mental health symptoms in individuals with mental disorders: systematic review and meta-analysis. BJPsych Open. 2025. https://doi.org/10.1192/bjo.2025.10885
Alsanie SA, Alhodieb FS, Askarpour M. Effects of ashwagandha (Withania somnifera) on mental health in adults: A systematic review and dose-response meta-analysis of randomized controlled trials. Complementary Therapies in Medicine. 2026. https://doi.org/10.1016/j.ctim.2026.103325
Albalawi AA. Dual impact of Ashwagandha: Significant cortisol reduction but no effects on perceived stress. A systematic review and meta-analysis. Nutrition and Health. 2025. https://doi.org/10.1177/02601060251363647
Cheah KL, Norhayati MN, Husniati Yaacob L, et al. Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLOS ONE. 2021. https://doi.org/10.1371/journal.pone.0257843
Fornalik M, Malkiewicz A, Adamczak D, et al. Hormonal Modulation with Withania somnifera: Systematic Review and Meta-Analysis of Randomized-controlled Trials. Planta Medica. 2026. https://doi.org/10.1055/a-2802-8363
Coope OC, Willems MET, Levington A, et al. 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. Pharmaceuticals. 2026. https://doi.org/10.3390/ph19050725
Zhu X, Zeng Q, Lei Y, Xu D. Effects of Withania somnifera (L.) Dunal (Ashwagandha) on cognitive and physical function in adults: a systematic review and meta-analysis. Frontiers in Pharmacology. 2026. https://doi.org/10.3389/fphar.2026.1799467
Lopresti AL, Drummond PD, Smith SJ. A Randomized, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha (Withania somnifera) in Aging, Overweight Males. American Journal of Men's Health. 2019. https://doi.org/10.1177/1557988319835985
Pérez-Gómez J, Villafaina S, Adsuar JC, et al. Effects of Ashwagandha (Withania somnifera) on VO2max: A Systematic Review and Meta-Analysis. Nutrients. 2020. https://doi.org/10.3390/nu12041119
Bonilla DA, Moreno Y, Gho C, et al. Effects of Ashwagandha (Withania somnifera) on Physical Performance: Systematic Review and Bayesian Meta-Analysis. Journal of Functional Morphology and Kinesiology. 2021. https://doi.org/10.3390/jfmk6010020
Li X, Li H, Yao S, et al. Effects of Withania somnifera (Ashwagandha) Supplementation on Exercise Performance: A Systematic Review and Three-Level Meta-Analysis. Nutrients. 2026. https://doi.org/10.3390/nu18121915
Lee JC, Heo AS. Adjunctive Ashwagandha (Withania somnifera) Supplementation and Resistance-Training Adaptations in Healthy Adults: A Systematic Review and Random-Effects Meta-Analysis of Muscular Strength, Chest Circumference, and Body Composition. Nutrients. 2026. https://doi.org/10.3390/nu18172815
Coope OC, Reales Salguero A, Spurr T, et al. Effects of Root Extract of Ashwagandha (Withania somnifera) on Perception of Recovery and Muscle Strength in Female Athletes. European Journal of Sport Science. 2025. https://doi.org/10.1002/ejsc.12265
Bokan G, Glamočanin T, Mavija Z, et al. Herb-Induced Liver Injury by Ayurvedic Ashwagandha as Assessed for Causality by the Updated RUCAM: An Emerging Cause. Pharmaceuticals. 2023. https://doi.org/10.3390/ph16081129
Björnsson HK, Björnsson ES, Avula B, et al. Ashwagandha-induced liver injury: A case series from Iceland and the US Drug-Induced Liver Injury Network. Liver International. 2020. https://doi.org/10.1111/liv.14393
Philips CA, Valsan A, Theruvath AH, et al. Ashwagandha-induced liver injury: A case series from India and literature review. Hepatology Communications. 2023. https://doi.org/10.1097/HC9.0000000000000270
Pakhale K, Salve J, Ademola J, et al. Safety of 8-Week Administration With Ashwagandha (Withania somnifera) Root Extract in Adults With Stress and Anxiety: Findings From a Prospective, Randomized, Multi-Center, Double-Blinded, Placebo-Controlled Study. Phytotherapy Research. 2026. https://doi.org/10.1002/ptr.70315
Bundesinstitut für Risikobewertung (BfR). Ashwagandha: Schlafbeeren-Präparate mit möglichen Gesundheitsrisiken. Mitteilung 039/2024. 2024. https://mobil.bfr.bund.de/cm/343/ashwagandha-schlafbeeren-praeparate-mit-moeglichen-gesundheitsrisiken.pdf
Tallon MJ, Koturbash I, Blum JL. A Systematic and Ethnobotanical Review of Ashwagandha's (Withania Somnifera) Teratogenic and Abortifacient Potentials. Phytotherapy Research. 2025. https://doi.org/10.1002/ptr.70079

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