Ashwagandha: The Benefits and Risks, With the Trial Numbers

Ashwagandha is the root of Withania somnifera, a shrub in the nightshade family used in Ayurvedic practice for centuries and sold in the UK as a food supplement with no authorised health claim. Its trials are small and short, and the results are modest: in a 2012 trial of 64 stressed adults, 600 mg of root extract a day for 60 days lowered serum cortisol by about 28% against 8% on placebo; in 60 people with insomnia, the same dose for 10 weeks shortened the time to fall asleep by about 5 minutes more than placebo; and in men, 23 pooled trials put testosterone about 57 ng/dL higher, inside the normal range, with no change in women.^{1, 2, 3} Two well-run stress trials found no difference from placebo, and about 25 published cases of liver injury sit beside 23 safety trials in 2,317 people whose liver tests stayed normal.^{4, 5, 6, 7} Regulatory position correct at 9 October 2026: legal in UK supplements, with the Food Standards Agency's safety assessment due shortly.

• What it is: a root extract standardised to withanolides; the root is what the trials used
• What the trials found: lower stress and anxiety scores with low certainty; about 5 minutes faster to sleep in insomnia; about 15% more testosterone in men; more strength in people who train
• Who should not take it: anyone pregnant, breastfeeding or under 18; anyone with liver disease or a thyroid condition, or on sedatives, immunosuppressants or thyroid medicine, without asking first

What is ashwagandha?

Ashwagandha is a small evergreen shrub, Withania somnifera, in the tomato family. Its small orange-red berries sit inside a papery husk, which is where its English name, winter cherry, comes from; the berry is not used. "Indian ginseng" is a nickname for its traditional role as a tonic, not a botanical relationship: it is unrelated to Panax ginseng, and it is a plant, not a mushroom (ashwagandha vs lion's mane compares the two). The root is the part Ayurvedic practice used and the part every trial in this guide tested; the leaves contain far more withaferin A, the compound behind most of the safety debate, which is why the plant part on a label matters.⁸ The active constituents are the withanolides, steroidal lactones to which extracts are standardised.

What does ashwagandha do to the body?

Laboratory work suggests withanolides act on GABA receptors; how that translates to people is not established. In people, the most complete picture is a 2026 pooling of 23 randomised trials in 1,706 adults: cortisol lower (standardised mean difference -1.18), serotonin higher, thyroxine up 0.61 µg/dL with TSH and T3 unchanged, and testosterone up in men only.³ What you notice when you start is usually nothing for a week or two: in the 23 safety trials, mild stomach upset, headache and drowsiness occurred at similar rates on placebo.⁷ It is a food supplement, not a medicine: the trials in insomnia, subclinical hypothyroidism, low sperm count and anxiety disorders are evidence, not licensed uses.

Does ashwagandha lower cortisol and stress?

The number everyone quotes comes from one trial. In 2012, 64 adults with chronic stress took 300 mg of root extract twice daily or placebo for 60 days: every stress scale fell more on ashwagandha, and serum cortisol fell 27.9% against 7.9% on placebo.¹ That single trial, on an extract its manufacturer supplied, is where "lowers cortisol by 30%" comes from. In 60 stressed adults in India, 240 mg a day for 60 days lowered Hamilton anxiety scores and morning cortisol against placebo.⁹ Pooled across 12 trials and 1,002 people, anxiety fell by a standardised mean difference of 1.55 and stress by 1.75, with the trials disagreeing widely (heterogeneity 84 to 94%) and low certainty.¹⁰ Nine trials pooled in 2024 give scale points: perceived stress 4.7 points lower on a 0 to 40 scale and Hamilton anxiety 2.2 points lower on a 0 to 56 scale, where 4 to 5 points is usually the threshold people notice.¹¹ Two careful trials were null: 60 adults on 225 or 400 mg a day of a root-and-leaf extract improved no more than placebo at 30 days, and 400 mg a day for 12 weeks in overweight adults aged 40 to 75 made no difference to perceived stress, though fatigue was lower.^{5, 4} No study has asked what a lower cortisol reading means for health.¹²

Should you test your cortisol first? No trial selected people by cortisol, a single reading swings by the hour, and GPs test cortisol to look for disease, not to plan a supplement. Nothing has been compared with ashwagandha head to head, so "what is more powerful" has no trial answer; for a diagnosed anxiety disorder the GP and NHS talking therapies come first. The brain, including the flatness some users describe, is on what ashwagandha does for the brain.

Does ashwagandha help you sleep?

By minutes. In 60 people with insomnia, 300 mg twice daily for 10 weeks shortened the time to fall asleep, measured by a wrist monitor, to 29.0 minutes against 33.9 on placebo, and raised sleep efficiency to 83.5% against 79.7%: about 5 minutes and 4 points.² Pooled over five trials of 400 people, four from one research group, the effect was moderate (standardised mean difference -0.59) and larger in diagnosed insomnia, at 600 mg a day and after 8 weeks or more.¹³ Sleep blends often pair a smaller ashwagandha dose than the trials used with magnesium, and any authorised wording on such a product belongs to the magnesium: it contributes to normal psychological function and to the reduction of tiredness and fatigue. Magnesium's own sleep trials are on does magnesium help you sleep, in the Wellgard sleep guide, and sour cherry's three small trials on do sour cherries help you sleep, what tart cherry is good for and tart cherry juice warnings. Melatonin is a prescription-only medicine in the UK, and no supplement is a source of it.

What does ashwagandha do for men?

Three measurable things. Testosterone: across the 23 pooled trials it rose by about 57 ng/dL in men, about 15%, within the normal range, with oestradiol unchanged.³ In 57 overweight men aged 40 to 70, salivary testosterone rose 14.7% more than on placebo over 8 weeks, with no difference in fatigue, vigour or sexual well-being.¹⁴ Strength: across 20 trials the effect was moderate (standardised mean difference 0.58), large in people who train (1.03) and absent in the untrained.¹⁵ In 57 young men new to resistance training, 300 mg twice daily for 8 weeks added 46.0 kg to the bench press against 26.4 kg on placebo.¹⁶ Fertility: in 46 men with low sperm counts, 675 mg a day for 90 days raised sperm count from 9.6 to 25.6 million per mL, a 167% rise, with little change on placebo; it is the only randomised trial in the 2018 fertility review.^{17, 18} So the testosterone answer is a number, not a boost; men with hormone-sensitive prostate cancer are advised against it for that reason.

What does ashwagandha do for women?

The stress, anxiety and sleep trials enrolled women and men together, so the numbers above are the best guide for women. The hormonal picture differs: testosterone did not rise significantly in women in the pooled trials, and oestradiol did not change.³ Three small placebo-controlled trials in India, of 100, 60 and 66 women, reported lower menopause-symptom scores than placebo over 8 to 12 weeks, and no product may claim a menopause effect.²⁴ Two cautions weigh more on women. Ashwagandha must not be taken in pregnancy or while breastfeeding, a caution stated on the pack. And because thyroid conditions are commoner in women, the one direction the trials show for thyroxine, up, matters: anyone with a thyroid condition or on levothyroxine asks their GP first.³

How long does ashwagandha take to work?

Weeks, not days. The trials reported their results at 6 to 12 weeks, a few ran to 180 days, and the one 30-day trial found no difference from placebo.^{5, 7} The insomnia trial measured at 10 weeks, the stress trials at 60 days, the strength trial at 8 weeks.^{1, 2, 16} Nothing happens within hours apart from drowsiness in some people; many take it in the evening, and those who feel "wired" take it in the morning with food. A fair personal trial is 8 weeks at a label dose, noting sleep, mood or training before and after. How long to continue, whether to cycle it and what happens when you stop are on is ashwagandha safe to take daily.

How do you read an ashwagandha label?

Three things decide what a product delivers. First, the plant part. A 2026 analysis tested 25 ashwagandha products on sale against the British and US Pharmacopoeia standards: 44% failed the British withanolide standard, 60% failed the American one, and only two were confirmed as made from root alone, the rest carrying undisclosed leaf or stem.⁸ Second, extract against whole root. A capsule stating "300 mg of a 10:1 root extract" and one stating "equivalent to 3,000 mg of whole root" describe the same dose; the trials used 240 to 600 mg a day of standardised root extract, so compare the extract figure with that. Third, standardisation: a stated withanolide percentage or milligrams of withanolide glycosides, as the trials' extracts had.

Formats differ in what a serving delivers. A capsule usually carries a standardised root extract in the hundreds of milligrams, with a root-only statement on the pack where that applies; a gummy usually carries a smaller extract dose, often with vitamin B6, and where B6 is present at 15% or more of the reference intake the wording on that pack belongs to the B6: vitamin B6 contributes to normal psychological function and to the reduction of tiredness and fatigue. Gummies, capsules and powders are not ranked here; the label says what each delivers. Ashwagandha itself has no authorised health claim in Great Britain, so no product carries one.

Is ashwagandha safe?

The liver first. To December 2025, 25 patients in 13 published reports developed liver injury linked to ashwagandha: it began typically 2 to 12 weeks after starting, with jaundice and itching; liver tests returned to normal within 1 to 5 months of stopping; one person needed a transplant; and three died, all with existing cirrhosis; chemical analysis found no adulterant.^{6, 19} Beside that sit 23 trials of standardised root-only extract in 2,317 healthy adults for up to 180 days, with liver, kidney, blood, hormone and heart markers inside normal ranges, in people screened for liver disease, so the trials cannot exclude a rare idiosyncratic reaction.⁷ Dark urine, pale stools, itching, yellow skin or eyes, nausea or pain under the right ribs mean stop and see a GP the same day, and a suspected reaction to any supplement can be reported to your local authority's trading standards or environmental health team, which works with the Food Standards Agency.²³ Thyroxine rises and TSH does not, so thyroid conditions and thyroid medicines need the GP's agreement first.³ Pregnancy, breastfeeding and under-18s: no. Sedatives, immunosuppressants, diabetes and blood-pressure medicines: tell your pharmacist. The dated record: Denmark prohibits ashwagandha in supplements after a 2020 assessment that could set no safe intake; the Dutch public-health institute advised against supplements and teas in March 2024; the French and German food-safety bodies advised in 2024 that pregnant and breastfeeding women, children and people with liver disease should not take it, without a ban; the UK Food Standards Agency ran a call for evidence from 8 July to 2 September 2024 and published its summary of 19 responses on 25 June 2026; the Committee on Toxicity discussed its third draft statement on 8 September 2026 and will publish it shortly.^{20, 21} The medicine table and the kidney, heart and thyroid questions are on who should not take ashwagandha.

Frequently asked questions

Is ashwagandha also called Indian ginseng, and what is its English name?

Yes, as a nickname for its traditional use as a tonic; it is not related to ginseng. Its English name is winter cherry, after the husked berries, and its botanical name is Withania somnifera, the species name meaning "sleep-inducing".

Is ashwagandha a steroid?

No. Ashwagandha is a plant root extract, not an anabolic steroid or a corticosteroid medicine, and it contains no hormone. Its active compounds, the withanolides, are called steroidal lactones because their carbon skeleton has the four-ring shape chemists call a steroid. In 23 pooled trials of 1,706 adults, testosterone rose by about 57 ng/dL in men, within the normal range, and did not change in women.³

Does ashwagandha help with weight loss or "cortisol belly"?

One trial of 52 adults under chronic stress recorded body weight as a secondary outcome over 8 weeks on 300 mg twice daily and reported it lower than on placebo without giving the size; no trial has measured weight or waist as its main outcome..²²

What does ashwagandha do to your face?

No trial has measured skin or facial appearance; the one thing to watch on the face is the liver warning: yellowing of the skin or eyes after starting ashwagandha is a reason to stop and see a GP that day.

What vitamins or drinks help with stress?

Two nutrients carry authorised wording: vitamin B6 and magnesium each contribute to normal psychological function, to normal functioning of the nervous system and to the reduction of tiredness and fatigue.

Sources

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