Quick answer

Ashwagandha is an Ayurvedic herb sold mostly as root extract. In small trials, 600 mg a day for about 8 weeks lowered stress scores and cortisol, which we grade as moderate evidence; findings for sleep, strength and menopause discomforts are early. It appears well tolerated for about 3 months, but it should be avoided in pregnancy.^1,2,3

Key facts

The amount most trials used was 600 mg of root extract a day, split into two capsules.^1,2
The seven stress trials NIH reviewed were small, lasted 6 to 8 weeks and were all run in India.²
Its most serious reported side effect is rare liver injury, usually starting 2 to 12 weeks after people began taking it.⁴
NIH lists several kinds of medicine it might interact with, including thyroid hormone and sedatives.^2,3

What ashwagandha is

Ashwagandha is Sanskrit for the smell of a horse, after the smell of the root. It is also called winter cherry or Indian ginseng, although it does not belong to the ginseng family.^2,4

In the Ayurvedic and Unani systems of India, the root is used as an adaptogen, loosely defined as something that helps a person resist or adapt to physical, chemical or biological stressors.²

Supplements usually contain an extract of the root, sometimes with leaf added. The species name, somnifera, comes from the Latin for sleep-inducing, and sleep and stress are what it is most often sold for.^2,5

The root is rich in withanolides and alkaloids. Withanolides are thought to account for many of its effects, though other compounds may also play a part.²

Some trials looked at other outcomes this site does not cover. The rest of this page sticks to what the trials measured for stress, sleep, strength training and menopause, and to safety.

What the evidence shows

Each claim below carries a grade and the daily amount the studies used. Only the stress claim reaches moderate. The others rest on a few small trials, nearly all run in India and often with extract supplied by its maker.^2,6

Helps the body handle occasional stress, with lower cortisol levels measured in trials*^1,2,7

Moderate evidence

Two placebo-controlled trials of a branded root extract at 600 mg a day (64 adults for 60 days; 60 adults in three groups for 8 weeks) found lower stress questionnaire scores and lower blood cortisol than placebo; in the larger trial cortisol fell 27.9% against 7.9% on placebo. NIH's summary of seven trials (491 adults, all in India) points the same way, but the trials were small and short and the maker supplied the extract.

Amount studied: 600 mg a day of root extract, as 300 mg twice a day, for 8 weeks to 60 days

Pooled analyses differ: a 2022 analysis of 12 trials with 1,002 people found lower stress scores but rated the certainty of the evidence low, and a 2025 analysis found lower cortisol but no clear change in self-rated stress.^8,9

May support sleep quality*^2,6

Early evidence

A meta-analysis of five small trials (400 adults, all in India; four used one branded root extract) found a small improvement in sleep over placebo, larger at 600 mg a day and after 8 weeks or more. The effect was strongest in people with diagnosed sleep problems; for healthy adults the evidence comes from three small trials of that extract.

Amount studied: Mostly 600 mg a day of root extract, for 6 to 12 weeks

May support strength gains when combined with resistance training*^10,11

Early evidence

Two 8-week trials of a branded root extract at 600 mg a day alongside a resistance training program (57 young men; 80 men and women) reported larger strength gains than placebo; in the first, bench press rose 46 kg against 26 kg. Both were run in India with extract supplied by the maker, and the first enrolled men with little training experience.

Amount studied: 600 mg a day of root extract (300 mg twice a day) for 8 weeks, with resistance training

A 2026 pooled analysis of 13 exercise trials found the most consistent effect on aerobic endurance, while the effect on strength was positive but uncertain. NIH's complementary health center says there is not enough evidence to judge ashwagandha for athletic performance.^3,12

May ease some self-rated discomforts around menopause*^13,14,15,16

Early evidence

Four small randomized trials in India gave women around or after menopause 250 to 600 mg a day of ashwagandha extract for 8 to 24 weeks, and each reported lower scores on menopause rating questionnaires than placebo. One, in 100 women, used 300 mg twice a day for 8 weeks; another, in 60 women aged 45 to 55, also counted fewer hot flashes. Two of the trials found higher estradiol and lower FSH and LH, a sign the extract can act on reproductive hormones.

Amount studied: 250 to 600 mg a day of root or root and leaf extract, for 8 to 24 weeks

How much people take

In several studies, results looked larger at 500 to 600 mg a day than at lower amounts. In the one trial that compared two amounts directly, stress scores and cortisol fell further on 600 mg a day than on 250 mg.^2,7

Root extract products often come as 150 to 600 mg capsules or tablets taken one to three times a day, so daily totals vary widely.⁴

Extracts differ in the part of the plant used and in their withanolide content, so 600 mg of one extract is not a known match for 600 mg of another. The dosage guide sets the trial amounts side by side.²

Root, leaf and standardized extracts

The root and the leaf differ in their chemical make-up, so a root and leaf extract is not the same product as a root-only extract.²

Extracts are standardized to different amounts of withanolides. Among the root extracts NIH describes, the share ranged from under 1% to about 5%, and one root and leaf extract held 21 mg of withanolide glycosides in a 60 mg capsule.²

Because studies used different preparations, made with different extraction and standardization methods, NIH says it is hard to name a specific extract or a recommended amount.²

What's in ours

What’s in ours

Ashwagandha Complex: KSM-66 Ashwagandha Extract, 600 mg per serving, from the label

Ashwagandha Complex lists 600 mg of a branded root extract per serving, standardized to 5% withanolides. That is the daily amount most of the trials above used, so the findings on this page were made at the amount the label provides.^1,2

Side effects, medicines, and who should avoid it

Common side effects are usually mild: upset stomach, loose stools, nausea and drowsiness. Vomiting has also been reported.^2,3,5

Rare cases of liver injury have been linked to ashwagandha, usually starting 2 to 12 weeks after people began taking it, with jaundice and itching. Most resolved within 1 to 4 months of stopping, but a few were fatal or needed a liver transplant, mainly in people who already had liver disease.^2,4

Ashwagandha may change thyroid hormone levels. In a trial of 50 people with a mildly underactive thyroid, 600 mg a day for 8 weeks lowered TSH and raised T3 and T4, and three women developed an overactive thyroid while taking it, which settled when they stopped.^2,17

Ashwagandha might raise testosterone levels, so experts say it might not be safe for men with hormone-sensitive prostate cancer.^2,3

NIH's complementary health center says ashwagandha should be avoided during pregnancy and not used while breastfeeding. Some reports suggested it could cause miscarriage, although the American Herbal Pharmacopoeia says its own report on the root has been misrepresented.^2,3

No upper limit has been set for ashwagandha. It appears well tolerated for up to about 3 months, and its safety over longer periods is not known.^2,3

Ask your pharmacist or doctor first

NIH says ashwagandha might interact with thyroid hormone medicines, such as levothyroxine. The concern comes from studies in which ashwagandha raised thyroid hormone levels, and from case reports of an overactive thyroid in people taking it.^2,3,5,18

Expected from how the two work, not shown in studies

Ask your pharmacist or doctor first

NIH's complementary health center says there is evidence that ashwagandha might interact with medicines for high blood pressure, and NIH's dietary supplement office lists them too. Neither says how large the effect might be or which medicines are most affected.^2,3,5

Reported in studies

NIH also lists diabetes medicines, sedatives, anti-seizure medicines and medicines that suppress the immune system among those ashwagandha might interact with.^2,3

Do not use it if you are pregnant or breastfeeding, or have hormone-sensitive prostate cancer³
Ask your doctor first if you have liver disease, a thyroid condition or an autoimmune condition^3,4
Ask first if you take any of the medicines above, or have surgery planned³
Ask first before giving it to anyone under 18, because the trials enrolled adults¹⁹

Stop taking it and see a doctor if you notice yellow skin or eyes, itching, nausea, unusual tiredness or stomach discomfort. These can be signs of liver injury.^2,4

Questions people ask

What does ashwagandha do for men?

The trial evidence specific to men is for strength training: in 57 young men lifting weights for 8 weeks, 600 mg a day went with larger strength gains than placebo, which we grade as early. Ashwagandha may also raise testosterone, which this site counts as a reason for caution, not a benefit.^2,10

Does ashwagandha help with sleep?

The evidence is early. A pooled analysis of five small trials found a small effect on sleep, larger at 600 mg a day and after 8 weeks or more. It can also make some people drowsy.^5,6

Does ashwagandha do anything for skin?

We found no trial of ashwagandha taken by mouth for the skin in the sources we use, so we make no claim about it.

Can ashwagandha harm the liver?

Rarely, yes. NIH's LiverTox database rates ashwagandha a likely cause of rare liver injury, usually 2 to 12 weeks after starting. Most people recovered within 1 to 4 months of stopping, but a few cases were fatal or needed a transplant, mainly in people who already had liver disease.⁴

Is ashwagandha banned anywhere?

Denmark banned it in supplements in 2023 after a risk assessment raised concerns about pregnancy and hormones. In 2024, France's food safety agency advised against its use by some groups, including pregnant and breastfeeding women and people with hormone conditions.²

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See the Full Measure line Ashwagandha Complex

Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.