Ashwagandha Benefits, Side Effects and Safety: What Studies Show

The ashwagandha benefits with the most research behind them are lower stress and anxiety scores and somewhat better sleep. Smaller studies have also looked at testosterone, sperm counts and strength training. Most of these trials were small, lasted 6 to 12 weeks, took place in India and often used extracts supplied or funded by the companies that make them. Side effects in trials were usually mild, but liver injury, thyroid changes and pregnancy concerns have been reported, and Denmark banned the herb in 2023. This guide explains what ashwagandha is, what the studies found, ashwagandha side effects, and who should avoid it.

Peptide Labs sells one product mentioned below. This article is general information, not medical advice.

What is ashwagandha?

Ashwagandha is Withania somnifera, an evergreen shrub in the nightshade family that grows in parts of Asia, Africa and Europe. The NIH Office of Dietary Supplements (ODS) explains that the Sanskrit name refers to the root’s smell, said to resemble a wet horse; it is also called winter cherry or Indian ginseng, although it is not a true ginseng. In Ayurvedic medicine it is used as an adaptogen, a loose term for something said to help the body resist stress. The species name somnifera means sleep-inducing in Latin.

Most supplements use an extract of the root; some combine root and leaf, which have different chemistry. The compounds studied most are withanolides. Research often names branded extracts: KSM-66 is a root-only extract, while Sensoril and Shoden use root and leaf. Because extracts differ, results from one do not automatically apply to another.

Ashwagandha benefits: what the research shows by outcome

Outcome	What trials found	Main caveats
Stress and anxiety	Lower rating-scale scores and serum cortisol vs placebo in most trials	Low certainty; very mixed results between studies; mostly India
Sleep	Small improvement, larger in people with insomnia	Five trials, about 400 people
Testosterone	Modest rises in some trials of men	Small, short; few studies at low risk of bias
Sperm parameters	Improvements in one pilot of 46 men	Pilot study; extract supplied by its maker
Strength training	Greater strength gains vs placebo in small trials	Mostly young men; review authors had industry ties

Stress and anxiety

ODS summarizes a 2021 review of seven trials with 491 adults, all in India, who took ashwagandha or placebo for 6 to 8 weeks. Stress and anxiety scores, sleeplessness, fatigue and serum cortisol fell more with ashwagandha. A 2022 meta-analysis of 12 trials with 1,002 participants reached a similar conclusion but rated the certainty of the evidence as low, partly because results varied widely between studies. Not every trial was positive: a 12-week study of 120 overweight adults with fatigue found less fatigue but no drop in perceived stress. An international psychiatry taskforce gave ashwagandha only a provisional recommendation for generalized anxiety disorder in 2022, saying more data are needed. If cortisol is your main interest, our cortisol belly guide compares ashwagandha with other ingredients sold for stress.

Sleep

A 2021 meta-analysis pooled five randomized trials with about 400 participants and found a small but significant improvement in overall sleep. The effect was clearer in adults with insomnia and in studies lasting at least 8 weeks. The authors noted that data on serious side effects were limited and that more safety data are needed before long-term use can be judged. All five trials were done in India. For another ingredient in many sleep formulas, see our magnesium for sleep guide.

Testosterone and male fertility

In a 16-week crossover trial of overweight men aged 40 to 70, 57 enrolled and 43 finished. Testosterone rose 14.7% more on ashwagandha than on placebo, but fatigue, vigor and sexual well-being did not differ between groups. The extract’s supplier funded the study. A pilot study of 46 men with low sperm counts reported higher sperm count, semen volume and motility after 90 days, using an extract provided by its maker. A 2021 review of 32 herb trials counted ashwagandha among the herbs with positive testosterone results, but judged only 6 of the 32 studies to be at low risk of bias. These studies do not show that ashwagandha addresses infertility or low testosterone; anyone with those concerns needs a medical evaluation.

Exercise and strength

In an 8-week trial, 57 young men new to weight training gained more bench-press and leg-extension strength and more arm and chest size on ashwagandha than on placebo; the extract came from its manufacturer. A 2021 meta-analysis of 12 studies in healthy people found ashwagandha outperformed placebo on physical performance measures, while calling for more comparable studies. One of its authors works for a company that sells an ashwagandha product.

Why the evidence is weaker than it looks

• Small and short. ODS describes most trials as fairly small and of short duration; effects beyond about 3 months are unknown.
• One setting. Most trials ran in India, within a traditional medical system, so results may not carry over to supplement use elsewhere.
• Industry involvement. Several trials used extracts provided by the companies that sell them, and at least one was funded by the extract’s supplier.
• Self-rated outcomes. Stress, anxiety and sleep were mostly measured with questionnaires, which are sensitive to expectation.
• Different products. ODS notes that varied extracts and preparations make it hard to say which product or amount was responsible for any effect.

Ashwagandha side effects

ODS and the National Center for Complementary and Integrative Health (NCCIH) list the common ashwagandha side effects as stomach upset, loose stools or diarrhea, nausea, vomiting and drowsiness. In trials these were usually mild. The rarer effects matter more:

• Liver injury. A 2020 case series from Iceland and the U.S. Drug-Induced Liver Injury Network described five people, aged 21 to 62, who developed jaundice 2 to 12 weeks after starting ashwagandha products. None had liver failure, and liver tests returned to normal within 1 to 5 months in the four who were followed. A 2023 Indian series reported eight cases from single-ingredient products; three people with existing liver disease developed liver failure and died. Ashwagandha joins other herbs, such as green tea extract, linked to rare liver injury.
• Thyroid changes. In a 50-person trial, ashwagandha lowered TSH and raised thyroid hormone levels, and three case reports describe thyrotoxicosis (an excess of thyroid hormone) that resolved after stopping.
• Hormones. Because ashwagandha may raise testosterone, experts cited by ODS say it might not be safe for men with hormone-sensitive prostate cancer.

In the case series, people developed yellowing of the skin or eyes, itching, nausea, tiredness and abdominal discomfort. Anyone who notices these signs while taking ashwagandha should stop it and contact a doctor.

Is ashwagandha safe? Who should avoid it

NCCIH says ashwagandha may be safe for short-term use, up to 3 months; long-term safety has not been studied. Government agencies advise these groups to avoid it or to ask a clinician first:

• Pregnant or breastfeeding women: NCCIH says to avoid it; the concern stems from reports of traditional use to induce miscarriage. The American Herbal Pharmacopoeia disputes that there is evidence the root causes abortion, but no study shows it is safe in pregnancy.
• People with thyroid disorders or who take thyroid hormone medicine.
• People with autoimmune conditions or liver disease.
• Anyone scheduled for surgery.
• People taking medicines for diabetes, blood pressure, seizures or immune suppression, or sedatives; ashwagandha may interact with them.
• Men with hormone-sensitive prostate cancer.
• Children and teens: France’s food safety agency advises against use under 18.

Bans and warnings outside the U.S.

In the U.S., ashwagandha is sold as a dietary supplement, and the FDA does not approve supplements before they reach shelves. Several European regulators have taken a more cautious line, mainly over pregnancy, thyroid and liver concerns:

Country	Year	Action
Denmark	2023	Banned ashwagandha in supplements after a 2020 Technical University of Denmark assessment found no safe intake limit could be set
Sweden	2023	Food agency said companies must be able to show their products are safe
France	2024	ANSES advised against use in pregnancy, breastfeeding, under 18, and with thyroid, liver or heart conditions or sedating medicines
Netherlands	2024	RIVM advised consumers, as a precaution, not to use it, especially during pregnancy
United Kingdom	2024	Food Standards Agency gathered evidence to inform future advice

As of mid-2026, no EU-wide restriction had been adopted. These actions reflect gaps in safety data rather than proof of harm at typical amounts, but they are a reason to read labels carefully and talk to a clinician. Our guide to third-party tested supplements explains how to check what a botanical product contains.

Ashwagandha in products we carry

InnoSupps Night Shred, from InnoSupps, lists 200 mg of KSM-66 organic ashwagandha root extract per two-capsule serving, alongside 3 mg of melatonin, magnesium, GABA, valerian, chamomile, passion flower, 5-HTP, L-tryptophan, CLA and L-carnitine. Its label is for adults at bedtime, excludes pregnant or lactating women, warns against alcohol, driving or operating machinery, and says to stop two weeks before surgery. Because it combines many ingredients, no single one can be credited with any effect, and its 5-HTP raises its own interaction questions; see our 5-HTP guide. Two other items in our catalog, a CBD nighttime softgel and a thermogenic pill pack, list ashwagandha inside proprietary blends without stating the amount.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Follow the label and ask a healthcare provider before starting any supplement, especially if you take medicines. 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.

Last reviewed September 2026.

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