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The benefits of ashwagandha

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The OneVit Team

The OneVit Team

Updated on

1st October 2026

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8 min

The benefits of ashwagandha

Ashwagandha is everywhere right now. And the benefits that its marketing claims can be a bit far-fetched.

So we've looked at the research behind ashwagandha benefits. Here's what the trials actually found, how it might work, and who should give it a miss.

What is ashwagandha?

Ashwagandha is a small shrub that grows in India, the Middle East and parts of Africa. Its scientific name is Withania somnifera.

Its root, and sometimes its leaves, have been used in Ayurvedic medicine for centuries. Traditionally, it's a rasayana: something believed to support vitality and resilience to everyday stress.

Today, most supplements use a standardised extract rather than raw powder.

The main active compounds are called withanolides. They're found mostly in the root. The withanolide percentage is used as a marker of an extract's strength and consistency.

Extracts vary a lot. Some use root only, while others mix root and leaf. Withanolide content can range from under 1% to 5% or more.

That's one of the main reasons results differ so much between studies, and between products. So "ashwagandha benefits" as a blanket term can be misleading. What matters is what was actually studied.

What does the research say about ashwagandha's benefits?

Short answer? The research on ashwagandha benefits is stronger than for most herbal supplements. But it's not as clear-cut as some of its marketing suggests.

Ashwagandha has been studied in a good number of randomised, placebo-controlled trials. Here's what they found, area by area.

Stress and cortisol

This is where the evidence is strongest.

Several trials have looked at adults with ongoing stress. Over six to eight weeks, people taking ashwagandha had bigger drops in stress questionnaire scores than those on a placebo.1,2

Some of these trials also found lower morning cortisol, your main stress hormone. Scores on anxiety questionnaires improved too.1,2

These results show up fairly consistently across independent trials. That's one reason ashwagandha is among the most researched herbal ingredients for stress.

There's a catch, though. Most people in these trials were already quite stressed at the start. The evidence for normal, everyday stress is less clear.

So think of these as findings from clinical research. They're not a guarantee of what it'll do for you.

Sleep

Ashwagandha won't send you to sleep. But trials looking at sleep have found modest improvements in sleep quality.3

The effect tended to be bigger in people whose sleep was already disrupted. People who were already sleeping well saw less of a difference.3

Researchers have suggested this may be linked to a mild calming effect on the nervous system.6

Muscle strength and testosterone

Testosterone is one of the more closely studied areas.

In a small 2013 trial, men with low sperm counts took ashwagandha root extract for 90 days. Their testosterone rose by 17%, and their sperm results improved too.4

A 2015 trial looked at men starting a resistance training programme. Compared with placebo, they saw greater gains in muscle strength and size.5

Markers of exercise-induced muscle damage also fell faster in these men. And their testosterone went up.5

Now for the small print. Most of this research involved two groups of men. Those doing resistance training, and those with below-average testosterone or sperm results to start with.

For men with normal testosterone, the picture is less clear. And the effect in women hasn't been well studied.

How does ashwagandha work?

Nobody knows for sure yet. But two possible pathways keep coming up in the research.

Your stress response. Your body has a stress response system that controls how much cortisol you release. Its scientific name is the hypothalamic-pituitary-adrenal (HPA) axis.

Several studies found lower morning cortisol alongside better stress scores. That suggests ashwagandha may dampen your stress response.2

A calming effect. Some of ashwagandha's compounds are thought to act on GABA. That's a chemical messenger that helps calm your nervous system.

Some prescription sedatives work on the same pathway. Ashwagandha's effect appears to be much milder, though.6

Neither pathway is fully mapped. Much of this research was done in animals or in the lab, not in people.

So the trial results are on firmer ground than the theories about why they happen. That goes for stress scores, sleep quality and hormone levels.

How much ashwagandha should you take, and when?

Most trials use 250mg to 600mg a day of a standardised extract. This is often split into two doses.1,3,12

Results are usually checked after eight to twelve weeks.1,3,12

There's no official recommended dose in the UK. That's because ashwagandha doesn't have a maximum permitted level under food supplement rules.

So sticking to a dose in line with the research is a sensible starting point. Do not take more than the recommended daily dose on the label.

When to take ashwagandha

Timing doesn't seem to make much difference in the research. You can take it with or without food.

Morning, evening or split across both are all fine. It depends on what suits you and why you're taking it.

If you're taking it for sleep, you might prefer an evening dose a few hours before bed. The trials don't point to one best time, though.

Is ashwagandha safe? Side effects and who should avoid it

In clinical trials, ashwagandha is generally well tolerated. But it isn't right for everyone.

Side effects

The most commonly reported side effects are mild:3

  • nausea
  • stomach upset
  • drowsiness
  • headache

There have been rare reports of liver injury linked to ashwagandha supplements.9

Many of the products involved mixed root and leaf, or weren't standardised. That makes it hard to pin down the exact cause.

Based on the safety data so far, root-only standardised extracts appear to carry a lower risk.8

If you notice side effects, stop taking it and speak to a pharmacist. If you notice yellowing of your skin or eyes or dark urine, stop taking it and speak to your GP as soon as possible.

Who should avoid ashwagandha?

Some people should skip ashwagandha altogether. Others should check with a GP or pharmacist first.

Pregnant or breastfeeding? Do not take ashwagandha if you are pregnant or breastfeeding. Animal studies suggest it may affect uterine contractions and hormone levels. There isn't enough human data to show it's safe.11

Thyroid conditions. Ashwagandha may raise thyroid hormone levels, which could affect your medication dose. Speak to your GP before taking ashwagandha if you have a thyroid condition.10

Sedatives, sleep or anti-anxiety medicines. Ashwagandha may add to their effects. Speak to your pharmacist before taking ashwagandha if you are on any of these.10

Diabetes or blood pressure medicines. Ashwagandha may slightly lower blood sugar and blood pressure. Speak to your GP or pharmacist before taking it. Watch for signs of low blood sugar or low blood pressure.10

Immunosuppressants. This includes people with autoimmune conditions or an organ transplant. Ashwagandha may stimulate immune activity. Do not take ashwagandha unless your specialist has advised it.10

Choosing an ashwagandha supplement

Ashwagandha products vary a lot in quality. Here's what to look for:

  • Root-only extract. These generally have a better safety profile than root and leaf blends.8
  • A standardised withanolide percentage. Look for a clearly labelled figure, often around 5%. Skip "ashwagandha powder" with no stated strength.
  • A dose in line with the research. Most positive trials used 250mg to 600mg a day of a standardised extract. Not a trace amount buried in a bigger blend.

Our Ashwagandha KSM-66 ticks all three boxes. It's a root-only extract with a standardised withanolide content.

You'll also find it in two of our blends. The Testosterone Support Complex pairs it with other ingredients associated with men's hormonal health. The Deep Sleep Complex is formulated for evening use.

Putting together a wider daily routine? Vitamins B6 and B12 contribute to normal psychological function and to the reduction of tiredness and fatigue.

That's why our B Complex is a common pairing with ashwagandha.

And remember, supplements are backup. They don't replace a varied, balanced diet.

Frequently asked questions

Does ashwagandha really work? There's more evidence for it than for most herbal supplements, especially on stress and cortisol. But most of the ashwagandha benefits seen in trials came from standardised, root-only extracts. These were taken for eight weeks or more, not generic powder taken short term.

How long does ashwagandha take to work? Most trials measured results after six to twelve weeks of daily use. Some people report noticing effects sooner. But the research supports giving it at least eight weeks before you decide.

Can you take ashwagandha every day? Yes. The trials in this article used daily doses for eight to twelve weeks without safety concerns. There's less data on longer-term use, though. So it's worth taking occasional breaks and talking to a pharmacist about longer use.

Can you take ashwagandha with magnesium or B vitamins? There's no known interaction between them, and they're often taken together. Trying a new combination? It's sensible to start one at a time, so you can see how each affects you.

What should I look for when buying an ashwagandha supplement? A root-only extract with a clearly stated, standardised withanolide percentage. Look for 250mg to 600mg a day. Be wary of blends that include ashwagandha without saying how much.

Does ashwagandha increase testosterone in everyone? Not necessarily. The clearest increases were in men doing resistance training, or with below-average testosterone or sperm results. In men with normal levels, or in women, the effect is less clear.

References

  1. Chandrasekhar K, Kapoor J, Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian J Psychol Med. 2012;34(3):255-262.
  2. Investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: a randomized, double-blind, placebo-controlled study. PMC. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750292/
  3. National Institutes of Health, Office of Dietary Supplements. Ashwagandha: Is It Helpful for Stress, Anxiety, or Sleep? Health Professional Fact Sheet. https://ods.od.nih.gov/factsheets/Ashwagandha-HealthProfessional/
  4. Ambiye VR, Langade D, Dongre S, et al. Clinical evaluation of the spermatogenic activity of the root extract of ashwagandha (Withania somnifera) in oligospermic males: a pilot study. Evid Based Complement Alternat Med. 2013;2013:571420.
  5. Wankhede S, Langade D, Joshi K, et al. Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. J Int Soc Sports Nutr. 2015;12:43. https://doi.org/10.1186/s12970-015-0104-9
  6. Sprengel M, Laskowski R, Jost Z. Withania somnifera (Ashwagandha) supplementation: a review of its mechanisms, health benefits, and role in sports performance. Nutr Metab (Lond). 2025;22. https://doi.org/10.1186/s12986-025-00902-7
  7. GOV.UK. Great Britain Nutrition and Health Claims (NHC) Register. https://www.gov.uk/government/publications/great-britain-nutrition-and-health-claims-nhc-register
  8. Comprehensive safety evaluation of Withania somnifera (Ashwagandha): an AI-driven meta-analysis and quantitative structure-activity relationship based toxicity assessment. PMC. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12682666/
  9. Liver Dangers of Herbal Products: A Case Report of Ashwagandha-Induced Liver Injury. PMC. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10002162/
  10. 5 Ashwagandha Interactions to Watch For. GoodRx. https://www.goodrx.com/well-being/supplements-herbs/ashwagandha-drug-interactions
  11. Ashwagandha: Is It Safe? Part 1: A Regulatory Review. Phytotherapy Research. https://onlinelibrary.wiley.com/doi/10.1002/ptr.70151?af=R
  12. Salve J, Pate S, Debnath K, Langade D. Adaptogenic and anxiolytic effects of ashwagandha root extract in healthy adults: a double-blind, randomized, placebo-controlled clinical study. Cureus. 2019;11(12):e6466. https://doi.org/10.7759/cureus.6466

This article is for informational purposes only and does not constitute medical advice. If you are pregnant, breastfeeding, managing a thyroid condition, or taking prescription medication, consult a GP or qualified healthcare professional before taking ashwagandha.

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