Ashwagandha: what the evidence shows, side effects and its status in the UK and EU

What is ashwagandha?

Ashwagandha (Withania somnifera) is a shrub used in Ayurvedic medicine. It’s marketed as an “adaptogen”, a plant said to help the body cope with stress. There’s no medical definition of the term.

Supplements usually contain root extract, sometimes a mix of root and leaf. Its active compounds are thought to be withanolides (a group of steroid-like plant chemicals). Products differ a lot in raw material, extraction method and dose, so the result of one trial doesn’t carry over to every bottle on the shelf.

What the evidence shows for stress and sleep

Stress and anxiety

According to NIH ODS, a 2021 systematic review covered 7 trials with 491 adults. All were run in India and lasted 6–8 weeks, with 240–1,250 mg of extract a day. Stress and anxiety scores and cortisol levels fell more than with placebo.

A 2022 meta-analysis pooled 12 trials with 1,002 participants and also found lower anxiety and stress. But the authors rated the certainty of the evidence as low, and the results varied widely between trials.

Sleep

A 2021 meta-analysis pooled five trials, all run in India. The authors describe “a small but significant effect” on sleep. It was larger at 600 mg a day or more, with at least 8 weeks of use, and in people with insomnia.

Doses used in trials

Most stress and sleep trials used 250–600 mg of root extract a day, and benefits were more often seen at 500–600 mg. A 2022 WFSBP and CANMAT taskforce of psychiatric societies provisionally recommended 300–600 mg of root extract standardised to 5% withanolides for generalised anxiety. It added that more research is needed. No safe dose has been set: in 2024 the BfR said a safe intake level couldn’t yet be derived.

How reliable is this evidence?

Points to weigh before you expect an effect:

• almost all trials are short, 6 to 12 weeks;
• some were funded by extract manufacturers;
• different trials used different extracts, so comparing them is hard;
• there are no authorised health claims for ashwagandha in the UK or the EU.

For chronic insomnia, cognitive behavioural therapy (CBT-I) is the first-line treatment. Melatonin is the best-studied sleep supplement, though it’s prescription-only in the UK. See our guide to sleep supplements for a comparison.

Ashwagandha side effects

In trials lasting up to 3 months, ashwagandha was mostly well tolerated. The usual complaints were:

• stomach upset and loose stools;
• nausea;
• drowsiness.

Serious problems are rare, but they are why regulators are reviewing it.

Liver

In a case series from Iceland and the US, five people developed jaundice after 2–12 weeks of use, often with itching and nausea. The liver injury was cholestatic or mixed, meaning bile flow was affected. No one developed liver failure, and tests returned to normal within 1–5 months in the four people who were followed up.

An Indian series described 8 people who took ashwagandha without other herbs. Five already had chronic liver disease. Three of them developed acute-on-chronic liver failure, and all three died. Testing found only natural plant compounds in the products, with no adulteration or contamination.

In July 2025 the Dutch pharmacovigilance centre Lareb reported eight new cases of liver injury since its 2023 warning. It noted that other ingredients or contamination couldn’t be ruled out. How the damage happens is still unknown.

Thyroid

In 50 people with subclinical hypothyroidism (an underactive thyroid without clear symptoms), 600 mg a day for 8 weeks lowered TSH and raised T3 and T4. Cases of thyrotoxicosis (too much thyroid hormone) have been reported. NIH ODS concludes that ashwagandha might interact with thyroid hormone medicines.

Hormones

Ashwagandha may raise testosterone. Experts therefore consider it potentially unsafe for men with hormone-sensitive prostate cancer.

If a bottle is already in your kitchen cupboard, go through the steps below: how long to take it, the liver and thyroid warning signs, and when to stop straight away.

Who should not take ashwagandha

Don’t take ashwagandha if:

• you’re pregnant or breastfeeding;
• it’s for a child or teenager;
• you have or have had liver disease.

Talk to your GP first if:

• you have a thyroid condition or take levothyroxine;
• you take diabetes medicines, blood pressure medicines, immunosuppressants, sleeping tablets or sedatives;
• you have hormone-sensitive prostate cancer.

In 2024, Germany’s Federal Institute for Risk Assessment (BfR) advised pregnant and breastfeeding women, children and people with liver disease not to take ashwagandha supplements. It advises everyone else to be cautious, because the data aren’t enough for a full risk assessment.

Dark urine, yellowing of the skin or eyes, itching or marked tiredness while taking it are reasons to stop at once and see a doctor.

Ashwagandha in the UK

Ashwagandha is legal to sell as a food supplement in the UK. In July 2024 the Food Standards Agency (FSA) opened a call for evidence on its safety, which closed in September 2024. The responses went to the Committee on Toxicity (COT) for a risk assessment, and the FSA says the outcome will be published.

In June 2026, Which? reported that the COT was still finalising its statement and that the FSA advises pregnant women and people with liver conditions to avoid ashwagandha supplements. We couldn’t confirm whether the final statement has been published since. Until then, follow that advice and the BfR’s.

Is ashwagandha banned in Europe?

Denmark is so far the only EU country with an outright ban. Elsewhere, national agencies have issued warnings and advise caution.

Lower-risk alternatives

If you want to fall asleep more easily and feel less wound up, start with routine: the same wake-up time, morning daylight, less caffeine after lunch. Supplements worth discussing with your GP:

• L-theanine, an amino acid from tea, usually 200 mg in studies;
• glycine for sleep, 3 g before bed in small studies;
• magnesium glycinate, if your diet is low in magnesium.

More options are in our sleep and stress section. If you take medicines, check our vitamin compatibility chart.

How to choose ashwagandha on iHerb

If your GP agrees and it’s legal where you live:

1. Choose a root-only extract. Most trials used root extract, and leaf preparations raise extra questions.
2. Pick a single-ingredient product. Herbal blends are harder to assess, and if you react you won’t know why.
3. Match the dose to trials: 300–600 mg of extract a day. Start at the lower end.
4. Limit use to 3 months at most; longer-term safety is unknown.
5. Prefer products with independent quality testing (USP, NSF or similar seals).
6. Stop straight away if you notice dark urine, yellowing skin or itching.