Ashwagandha: the complete guide

What is ashwagandha?

Ashwagandha (Withania somnifera) is a small shrub from India, the Middle East and parts of Africa. Its root has been used for centuries in Ayurveda, India's traditional medicine. Today it is one of the most researched plant supplements, with dozens of human trials on sleep, stress, focus and exercise.

The name comes from Sanskrit and is often translated as "smell of the horse", after the root's strong smell. You may also see it called Indian ginseng or winter cherry, although it isn't related to true ginseng.

Its main active compounds are withanolides, natural plant chemicals used to measure an extract's strength. Most research uses branded extracts, made to a fixed recipe so every batch is the same:

• KSM-66. Root only, standardised to 5% withanolides. The most studied.
• Sensoril. Root and leaf, used at 125 to 500 mg a day in recent trials.
• Shoden. Root and leaf, used at lower doses of 60 to 240 mg a day.

These extracts aren't interchangeable. A result found with one doesn't automatically carry over to another.

How does ashwagandha work?

Ashwagandha is called an adaptogen: a plant thought to help the body respond to stress. Researchers think it acts on the system that controls cortisol, the body's main stress hormone.

That fits with what trials measure. Across 23 trials with 1,706 people, a 2026 review found ashwagandha lowered cortisol compared with a placebo [9]. How it does this in detail isn't fully known, and most of that work comes from lab studies rather than people.

What are the benefits of ashwagandha?

The best human evidence is for sleep and for cortisol. Research on focus, exercise and hormones is newer. Each finding has a label: Strong (several good trials agree), Moderate, Early (one or two small trials) or Mixed.

Sleep quality Moderate

A review of 5 trials with 400 adults found ashwagandha improved overall sleep more than a placebo. The effect was small, and it was larger at 600 mg a day or more and after 8 weeks or longer [1].

In one of the larger single trials, 150 healthy adults who woke up feeling unrefreshed took 120 mg of Shoden or a placebo for 6 weeks. Self-rated sleep quality rose by 72% with ashwagandha, against 29% with the placebo. Sleep trackers showed people fell asleep sooner and slept longer [2].

Cortisol Moderate

Cortisol is the most consistent finding. A 2025 review found it was on average 1.16 µg/dL lower than with a placebo, in trials using 250 mg a day or more [6]. The 2026 hormone review of 23 trials reached the same conclusion [9].

Feeling stressed Mixed

Many trials enrol healthy adults who say they feel stressed. The results point in a good direction but don't all agree:

• 52 adults under long-term stress. 300 mg of root extract twice a day for 8 weeks lowered stress scores more than a placebo [3].
• 60 stressed adults. 240 mg of Shoden a day for 60 days lowered morning cortisol. One stress questionnaire improved and another only came close [4].
• 111 adults aged 40 to 75. 400 mg a day of a different extract for 12 weeks didn't lower stress scores more than the placebo, though tiredness improved [5].
• Across 6 trials with 488 people. The 2025 review found felt stress wasn't clearly lower than with a placebo, even though cortisol was [6].

Focus and memory Early

A 2026 review of 20 trials with 1,249 adults found better memory, attention and processing speed than with a placebo [7]. The trials were small and used different extracts and tests, so how much this matters day to day is still unclear.

Exercise and strength Moderate

A 2026 review of 13 trials with 599 mostly young, active adults found better exercise performance on average. The clearest effect was on endurance, such as VO2max. Doses of 500 to 600 mg a day had the most support [8].

In one well-known trial, 57 young men new to weight training took 300 mg of root extract twice a day or a placebo for 8 weeks. Their bench press rose by 46 kg on ashwagandha, against 26 kg on placebo [10].

What the research says

These are the main studies behind this guide. Most were funded by the company that makes the extract, which is normal in this field.

Ashwagandha for men and for women

Most sleep and stress trials included both men and women and found similar results. The differences show up in hormones.

• Men. The 2026 hormone review found testosterone rose by about 57 ng/dL on average in men [9]. In 57 men aged 40 to 70, Shoden raised testosterone by 14.7% more than a placebo over 8 weeks, but tiredness and vigour didn't differ [11].
• Women. The same review found no change in testosterone or oestrogen in women [9]. For sleep and stress, women can expect the same mixed-to-moderate picture as men.

Don't take ashwagandha if you're pregnant or breastfeeding. There isn't enough safety research.

How to read an ashwagandha label

Look for three things: the extract's name, its amount in mg, and its withanolide percentage. Multiply the last two to get the withanolides you take.

Ignore "equivalent to" figures. A 600 mg extract made at 10:1 can be labelled "equivalent to 6,000 mg of root". That sounds bigger but gives you nothing extra.

How much ashwagandha should you take?

Most root extract trials used 300 to 600 mg a day, often split into two doses. Shoden trials used 60 to 240 mg, because that extract is more concentrated. The sleep review found bigger effects at 600 mg or more [1].

More isn't always better. Follow the dose on your product's label, and don't combine several ashwagandha products.

Capsules, gummies, powder or coffee?

• Capsules. Almost all the research used capsules of a standardised extract, so this is the closest match to the trials.
• Gummies. Easy to take, but often lower in extract, and many contain sugar. Check the extract name and amount per gummy.
• Powder. Usually whole root powder, not an extract, so you need much more of it. It tastes bitter and earthy.
• Coffee and drinks. No trials have tested them. Many contain a small amount, so check the label.

When to take it and how long it takes

• Any time of day. Trials gave it in the morning, at night or both. Pick the time you'll stick to.
• For sleep, many choose the evening. There is no proof that evening works better, but it fits a wind-down routine.
• With food if needed. Take it with a meal if it upsets your stomach.
• Give it 8 weeks. Most trials ran for 6 to 12 weeks, and the sleep review found bigger effects after 8 weeks [1].

Is ashwagandha safe?

In trials of up to 12 weeks, side effects were usually mild: stomach upset, loose stools and drowsiness [14]. In a 12-month study of 191 adults taking 600 mg of KSM-66 a day, there were 18 mild side effects and no meaningful change in liver tests. That study had no placebo group [12].

The rare but serious concern is the liver. Doctors in Iceland, the US and India have reported liver injury in people taking ashwagandha, usually 2 to 12 weeks after starting [15, 16]. Most recovered once they stopped. The US LiverTox database rates it a likely but rare cause [13].

• Don't take it if you are pregnant or breastfeeding, are under 18, or have liver disease.
• Thyroid. Ashwagandha may raise thyroid hormone a little [9]. Ask your GP first if you have a thyroid condition or take thyroid medicine.
• Ask your GP or pharmacist first if you have an autoimmune condition, have surgery planned, or take medicines for diabetes, blood pressure or your immune system, or sedatives.

Is ashwagandha banned in the UK?

No. Ashwagandha is legal to sell as a food supplement in the UK. Denmark banned it in supplements in 2023, and the UK Food Standards Agency is reviewing its safety. We'll update this guide if the UK position changes.

Ashwagandha and alcohol

No trial has tested it. Both alcohol and ashwagandha can make you drowsy, and both are processed by the liver. So keep alcohol low while you take it, and avoid it if you notice extra drowsiness.

Where Nooroots fits

Nooroots Ashwagandha + Lion's Mane gives you 120 mg of KSM-66 and 500 mg of lion's mane extract in two caffeine-free capsules a day. It's made for calm focus on demanding days, as part of a morning routine.

KSM-66 is a root-only extract standardised to 5% withanolides, and every amount is on the label.

Frequently asked questions

Is ashwagandha safe to take every day?

For most healthy adults, daily use in trials of up to 12 weeks was well tolerated, and a 12-month study found no safety concerns [12]. Rare liver injury has been reported, so avoid it if you have liver disease.

Does ashwagandha lower cortisol?

In several trials, yes. A 2025 review found cortisol was 1.16 µg/dL lower on average than with a placebo [6].

What is ashwagandha good for?

The best evidence is for sleep quality and lower cortisol. Research on stress, focus and exercise is promising but mixed or early.

How long does ashwagandha take to work?

Give it about 8 weeks of daily use. Most trials ran for 6 to 12 weeks [1].

Can you take ashwagandha with magnesium?

Yes, no interaction is known. See Ashwagandha and magnesium: can you take them together?

Can you take ashwagandha with lion's mane?

Yes, no interaction is known, though no trial has tested them together. See our lion's mane guide.

Does ashwagandha make you sleepy?

Drowsiness is one of the more common mild side effects [14]. If it affects you, take it in the evening.

Related articles: Magnesium glycinate and Lion's mane.

References

Every study here is listed so you can read it yourself. This guide is for general information and doesn't replace advice from your GP or pharmacist. We review it when new research is published.

1. Cheah KL et al. (2021). Effect of Ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis. PLOS ONE 16(9): e0257843. doi:10.1371/journal.pone.0257843
2. Deshpande A et al. (2020). A randomized, double blind, placebo controlled study to evaluate the effects of ashwagandha (Withania somnifera) extract on sleep quality in healthy adults. Sleep Medicine 72: 28–36. doi:10.1016/j.sleep.2020.03.012
3. Choudhary D et al. (2017). Body weight management in adults under chronic stress through treatment with ashwagandha root extract: a double-blind, randomized, placebo-controlled trial. Journal of Evidence-Based Complementary & Alternative Medicine 22(1): 96–106. doi:10.1177/2156587216641830
4. Lopresti AL et al. (2019). An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: a randomized, double-blind, placebo-controlled study. Medicine 98(37): e17186. doi:10.1097/MD.0000000000017186
5. Smith SJ et al. (2023). Exploring the efficacy and safety of a novel standardized ashwagandha (Withania somnifera) root extract (Witholytin) in adults experiencing high stress and fatigue in a randomized, double-blind, placebo-controlled trial. Journal of Psychopharmacology 37(11): 1091–1104. doi:10.1177/02698811231200023
6. Albalawi AA (2025). Dual impact of Ashwagandha: significant cortisol reduction but no effects on perceived stress. A systematic review and meta-analysis. Nutrition and Health 31(4): 1395–1408. doi:10.1177/02601060251363647
7. Zhu X et al. (2026). Effects of Withania somnifera (Ashwagandha) on cognitive and physical function in adults: a systematic review and meta-analysis. Frontiers in Pharmacology 17: 1799467. doi:10.3389/fphar.2026.1799467
8. Li X et al. (2026). Effects of Withania somnifera (Ashwagandha) supplementation on exercise performance: a systematic review and three-level meta-analysis. Nutrients 18(12): 1915. doi:10.3390/nu18121915
9. Fornalik M et al. (2026). Hormonal modulation with Withania somnifera: systematic review and meta-analysis of randomized-controlled trials. Planta Medica 92(8): 790–805. doi:10.1055/a-2802-8363
10. Wankhede S et al. (2015). Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. Journal of the International Society of Sports Nutrition 12: 43. doi:10.1186/s12970-015-0104-9
11. Lopresti AL et al. (2019). A randomized, double-blind, placebo-controlled, crossover study examining the hormonal and vitality effects of ashwagandha (Withania somnifera) in aging, overweight males. American Journal of Men's Health 13(2): 1557988319835985. doi:10.1177/1557988319835985
12. Salve J et al. (2026). Safety of 12-months administration of ashwagandha (Withania somnifera) standardized root extract in healthy adults: a prospective, observational study. Phytotherapy Research 40(8): 4802–4812. doi:10.1002/ptr.70096
13. LiverTox (updated 3 December 2024). Ashwagandha. National Institute of Diabetes and Digestive and Kidney Diseases. ncbi.nlm.nih.gov/books/NBK548536
14. National Center for Complementary and Integrative Health (updated March 2023). Ashwagandha. nccih.nih.gov/health/ashwagandha
15. Björnsson HK et al. (2020). Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver International 40: 825–829. doi:10.1111/liv.14393
16. Philips CA et al. (2023). Ashwagandha-induced liver injury: a case series from India and literature review. Hepatology Communications 7: e0270. doi:10.1097/HC9.0000000000000270