Ingredient evidence
Ashwagandha
The most popular adaptogen in the UK, with genuinely interesting stress data and a set of cautions that rarely make it onto the label.
Also sold as: Withania somnifera, KSM-66, Sensoril.
Our read of the evidence
Mixed evidence
Trials disagree, or the effect is small and inconsistent.
The stress data is better than most adaptogens, but the cautions are real. Not a supplement to take casually.
What the evidence actually shows
Several randomised placebo-controlled trials report reduced perceived stress scores and lower morning cortisol with standardised root extract at 300-600mg daily. Sleep quality also improves in some trials. The studies are mostly small, often manufacturer-funded, and heavily weighted towards specific branded extracts.
That said, the consistency is better than for most herbal stress products, and the effect sizes are not trivial. It is fair to call it promising. It is not fair to call it proven, and it is definitely not a treatment for an anxiety disorder.
Effects build over weeks rather than hours. Anyone expecting a same-day calming effect will be disappointed, and anyone who feels a strong immediate effect is probably experiencing expectation.
The cautions that matter
Ashwagandha can increase thyroid hormone levels. For someone with subclinical hypothyroidism that might sound useful, but for anyone on levothyroxine or with an overactive thyroid it is a genuine problem and can destabilise treatment.
There have been case reports of liver injury associated with ashwagandha products, prompting safety reviews in several countries. Rare, but real. Stop immediately and seek advice if you develop jaundice, dark urine or persistent nausea.
It should not be taken in pregnancy - traditional use includes abortifacient properties and there is no adequate safety data. It may also add to the effect of sedatives and immunosuppressants.
How to take it.
- Typical dose
- 300-600mg standardised root extract daily
- Form
- Root extract, standardised to withanolide content
- Timing
- Evening if using for sleep; with food to reduce stomach upset
- Worth knowing
- Assess at 8-12 weeks. Most trials did not run beyond three months, so long-term continuous use is not well studied.
What it will not do.
- It will not treat an anxiety disorder or depression
- It will not balance your hormones - that phrase means nothing here
- It will not work immediately; give it eight weeks or not at all
Who should avoid it.
- You are pregnant or trying to conceive
- You have a thyroid condition or take levothyroxine, without medical advice
- You have liver disease
- You have an autoimmune condition or take immunosuppressants, without advice
Raise with a prescriber
- May raise thyroid hormone levels and destabilise thyroid medication
- May add to the effect of sedatives, benzodiazepines and alcohol
- May interfere with immunosuppressant therapy
Products containing ashwagandha.
Everything below is stocked in the UK. Compare on the active dose and the cost per day rather than the size of the pack.
| Product | Key actives | Form | Price | Per day | Best for |
|---|---|---|---|---|---|
| De-StressThe Nue Co. | KSM-66 ashwagandha 500mg | Capsule | £35 | £1.17 | Chronic stress, Anxiety without medication, Poor sleep from cortisol |
| Wild Nutrition KSM-66 Ashwagandha PlusWild Nutrition | KSM-66 ashwagandha | Capsule | £30.00 | £1.00 | Short trials for stress and sleep |
| DR.VEGAN PMS HeroDR.VEGAN | Chasteberry, Vitamin B6, Magnesium, Ashwagandha | Capsule | £26.99 | 90p | Premenstrual symptoms, as a time-limited trial, Broken sleep, Night-time cramps |
| Together Health Whole Root AshwagandhaTogether Health | Whole root ashwagandha | Capsule | £14.95 | 50p | Short trials for stress and sleep |
Prices are the brand's UK list price at the time of writing and change often. Cost per day is calculated from pack size and the label's daily serving, and is shown only where both are published.
Common questions.
Does ashwagandha actually reduce stress?
Trials at 300-600mg daily show modest reductions in perceived stress and cortisol over 8-12 weeks. The effect is real but moderate, and many studies are funded by extract manufacturers.
Can I take ashwagandha with thyroid medication?
Not without medical advice. Ashwagandha can raise thyroid hormone levels and destabilise treatment.
Is ashwagandha safe long term?
Most trials ran for under three months, so long-term use is not well studied. Given the liver reports, periodic breaks and medical awareness are sensible.
Can I take ashwagandha in pregnancy?
No. It is not considered safe in pregnancy and should be avoided if you are trying to conceive.
Where this comes from.
A supplement is not clinical care.
If symptoms are affecting your work, your sleep or your relationships, the useful next step is an assessment rather than another purchase. Our check-in takes three minutes and points you to the right kind of clinician.
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Other ingredients
Reasonable evidence. Genuinely useful if you are low in magnesium or sleeping badly. Not a sedative, and not a cure for anxiety.
Mixed evidence. A reasonable, cheap thing to try for PMS at 50-100mg. Never go above the labelled limit.
Good evidence. Worth taking if you rarely eat oily fish, and genuinely important in pregnancy. Not a mood treatment on its own.
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Food supplements are not medicines and are not intended to diagnose, treat or cure any condition. They should not replace a varied diet or prescribed treatment. If you are pregnant, breastfeeding, taking medication or managing a diagnosed condition, check with a pharmacist or clinician before starting anything on this page. We do not accept payment for inclusion or placement. Where a link earns us a commission we say so on the product page. Last reviewed 27 August 2026.