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Awaiting clinical review. This entry is sourced but has not yet been signed off by a pharmacist or clinician.

Withania somnifera (root)

Ashwagandha

Ashwagandha root extract probably eases anxiety symptoms and sleep problems a little: meta-analyses of small trials lean positive, but the trials are short, mostly small, and the evidence for reducing perceived stress is split. Rare cases of liver injury have been reported, so it is not risk-free, and it should be avoided in pregnancy. Long-term safety (beyond about three months) is unknown.

Updated
29 September 2026
Ashwagandha root and powder in a small bowl
At a glance
Last reviewed 29 September 2026
Evidence
Moderate
Best for
Anxiety and sleep
Typical form & use
Root extract, 250–600 mg a day
Onset
4+ weeks
Safety
Rare liver injury; avoid in pregnancy. 5 known interactions, most serious with immunosuppressants.
Check with your medications →

What it's used for

Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.

UseEvidenceWhat the research shows
Anxiety symptomsModerateA meta-analysis of 9 randomised trials (558 people) found a lower Hamilton Anxiety score than placebo (mean difference -2.19 points). A later meta-analysis of 15 trials (873 people) reported a larger fall at 8 weeks (-3.52 points). NCCIH still calls the anxiety findings inconclusive, and the trials are small and short, so this is moderate rather than strong.1,2,6
Sleep and insomniaModerateA meta-analysis of 5 randomised trials (400 people) found a small-to-moderate improvement in overall sleep (standardised mean difference -0.59), with larger effects in people diagnosed with insomnia, at 600 mg a day or more, and for 8 weeks or longer. Only five trials, with moderate inconsistency between them (I² 62%).4,6
Perceived stress and cortisolLimitedReviews disagree. One found lower Perceived Stress Scale scores (mean difference -4.72 across 9 trials) and another found a fall of about 4.9 points at 8 weeks. A separate review of 6 trials (488 people in total) found lower cortisol but no significant effect on perceived stress. Cortisol falling does not by itself show that people feel less stressed, and because one review is null this use is capped at Limited.1,2,3
Male fertilityLimitedA systematic review found raised sperm concentration and motility in men with low sperm counts after about 90 days, but it included only one randomised trial and the rest were before-and-after studies. A later review of hormone outcomes found testosterone rose in men (about 57 ng/dl on average) but not in women. NCCIH calls the evidence for fertility limited.5,8,6

How much

Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.

Studied range
250–600 mg a day of root extract3,4
One review only included trials of 250 mg a day or more. The sleep review found bigger effects at 600 mg a day or more. Trials use extracts, and their strength differs between brands, so a dose of raw root powder is not comparable.
Duration studied
8 weeks or longer4,6
The sleep meta-analysis found larger effects with 8 weeks or more of treatment. NCCIH says it appears safe for up to about 3 months, and that long-term safety data are lacking.
Upper limit
Not established6
None of the sources we opened sets a safe upper intake. NCCIH gives no dosing recommendation.
Timing · The trials we read describe daily dosing over weeks; we did not find a source establishing a best time of day. If it makes you drowsy, taking it in the evening is a practical choice, but that is not a tested recommendation.With food? · Not established in the sources we read. NCCIH lists stomach upset among possible side effects, so taking it with food is reasonable.How long to trial · Judge it over 8 weeks, which is the length most trials ran. Stop and speak to a doctor if you develop yellow skin or eyes, dark urine, itching, or persistent nausea.

How people take it

Capsule or tablet (root extract)250–600 mg a dayThe form used in most trials. Check the label states the plant part (root) and extract, not just 'ashwagandha'.
Root powderNo trial-based doseTraditional form. We found no dose established from the trials we read, and extracts cannot be assumed equivalent.

Safety

Who should avoid
  • Pregnancy and breastfeeding — NCCIH advises avoiding it
  • Thyroid disorders, or if you take thyroid hormone — ask first
  • Autoimmune conditions — ask first (NCCIH advises against)
  • Before surgery — NCCIH advises against; tell your surgical team
  • Hormone-sensitive prostate cancer — it may raise testosterone
  • Existing liver disease, or any earlier liver reaction to supplements
Known interactions
CautionImmunosuppressants — NCCIH lists immunosuppressants as a possible interaction and advises against use with autoimmune conditions.
CautionSedatives & sleep medication — NCCIH lists sedatives as a possible interaction and drowsiness as a side effect, so effects could add up.
CautionThyroid medication — NCCIH lists thyroid hormone medicines as a possible interaction, and a hormone meta-analysis found ashwagandha modestly raised T4, so it could add to thyroid replacement.
MonitorBlood pressure medication — NCCIH lists blood pressure medicines as a possible interaction; the sources we read do not quantify the effect.
MonitorDiabetes medication — NCCIH lists diabetes medicines as a possible interaction; the sources we read do not quantify the effect.

Compare with

Head-to-head pages for the pairs people search most.

Ashwagandha vs L-TheanineAshwagandha vs Rhodiola

Questions people ask

Does ashwagandha really reduce stress?

It lowers cortisol in most trials, but whether people feel less stressed is disputed: one review found lower Perceived Stress Scale scores, another of six trials found no significant change. Anxiety scores show a clearer benefit, though the trials are small and short.

Is ashwagandha safe for the liver?

Usually, but not always. A case series of five people described jaundice and itching starting 2 to 12 weeks after beginning ashwagandha supplements, with liver tests returning to normal within 1 to 5 months in four of them and no liver failure. Four of the five were also taking other supplements. Stop and get medical advice if you notice yellowing of the skin or eyes, dark urine or itching.

How long does ashwagandha take to work?

The trials ran for about 8 weeks or more, and the sleep review found bigger effects at 8 weeks or longer. Do not expect an effect in days.

Can I take ashwagandha while pregnant?

No. NCCIH advises avoiding it during pregnancy and breastfeeding.

Sources

  1. Systematic review Velan A, Venugopal V, Balakrishnan A, et al. Effects of Ashwagandha (Withania Somnifera) on stress and anxiety: A systematic review and meta-analysis. Explore (NY). 2024;20(6):103062.
  2. Systematic review Bachour G, Samir A, Haddad S, et al. Effects of Ashwagandha Supplements on Cortisol, Stress, and Anxiety Levels in Adults: A Systematic Review and Meta-Analysis. BJPsych Open. 2025.
  3. Systematic review Albalawi AA, et al. Dual impact of Ashwagandha: Significant cortisol reduction but no effects on perceived stress - A systematic review and meta-analysis. Nutrition and Health. 2025;31(4):1395-1408.
  4. Systematic review Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R. Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS One. 2021;16(9):e0257843.
  5. Systematic review Durg S, Shivaram S, Bavage S. Withania somnifera (Indian ginseng) in male infertility: An evidence-based systematic review and meta-analysis. Phytomedicine. 2018;50:247-256.
  6. Regulator / government health agency National Center for Complementary and Integrative Health (NCCIH). Ashwagandha: Usefulness and Safety.
  7. Case series 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 Int. 2020;40(4):825-829.
  8. Systematic review Fornalik M, Malkiewicz A, Adamczak D, et al. Hormonal Modulation with Withania somnifera: Systematic Review and Meta-Analysis of Randomized-controlled Trials. Planta Med. 2026;92(8):790-805.

Last reviewed 29 September 2026 · Next review March 2027 · How we rate evidence