Ashwagandha is an Ayurvedic root, used for centuries as a Rasayana, a rejuvenating tonic, and taken today mostly for stress and sleep. The small trials that exist point the same way: over eight to twelve weeks a standardized root extract lowers stress-scale scores and morning cortisol and produces a small, steady improvement in sleep, with modest strength and testosterone gains in men who lift. The limit is evidence quality.
Almost every positive trial is small, runs a couple of months, and tests one branded extract, often funded by the company that makes it. The plant also carries cautions: rare liver injury, a rise in thyroid hormones, and no safety data in pregnancy. A standardized root extract at 300 to 600 mg a day for a defined stretch is the studied approach, and the sections below give the research, the dose and form, the Ayurvedic and Chinese medicine framing, and who should not take it.
Findings & Outcomes
What It Is
Ashwagandha (Withania somnifera) is a small shrub whose root has been used for centuries in Ayurveda, the traditional medicine of India, where it is classed as a Rasayana, a rejuvenating tonic. It is not a Chinese herb and has no entry in the classical Chinese Materia Medica. It belongs to the nightshade family, the same botanical group as tomato, potato, and bell pepper.
Modern supplements use the root, usually as a standardized extract concentrated for compounds called withanolides, and the two most-studied products are branded extracts sold under their own names. People take it mainly to feel less stressed and to sleep better, and that is where the human evidence is strongest, though strongest here still means small and short.
Anatomy of the Practice
1A root, standardized to withanolides
The active preparation is a concentrated root extract. Its withanolide content is what a product is standardized to, and it differs from brand to brand, which is one reason a result shown for one extract does not automatically carry to another. It is a plant with many compounds acting at once.
2On the stress axis
The best-mapped effect is on the hypothalamic-pituitary-adrenal axis, the loop that governs the stress hormone cortisol. In trials, ashwagandha lowered morning cortisol more than placebo, which is the mechanism the researchers point to for its effect on how stressed people feel.
3Active across several systems
The same broad activity acts on the thyroid, the immune system, and the nervous system as well. That breadth is why several situations call for care, all collected in the Cautions section below.
What It Does
Ashwagandha's evidence falls into two lines of very different strength.
The stronger line is the one its own tradition points to: a tonic for someone under strain. Over eight to twelve weeks a standardized root extract lowers stress-scale scores and morning cortisol against placebo, a 2022 meta-analysis pooled a large average drop in anxiety, and a separate analysis of five trials in 400 people found a small, steady improvement in sleep, clearest at 600 mg a day and in people who actually have insomnia. Stress and sleep are what most people take it for, and they are where the trials cluster.
The weaker line covers the body. In 57 untrained young men, ashwagandha alongside eight weeks of resistance training added more strength and testosterone than placebo, and a mixed-sex stress trial saw testosterone rise in men but not women. That is a thin, early base in selected male groups, and ashwagandha is not a treatment for low testosterone.
One caveat sits over both lines and sets how much weight each finding carries. Almost every positive trial is small, runs eight to twelve weeks, and tests a single branded extract, often with the company that makes the extract connected to the study. The direction is consistent across trials; the magnitude is not settled. Read each finding as specific to the extract and dose that were tested, and as a short-term signal that has not been shown to hold over many months.
The Research & Studies
Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.
Anxiety And Stress
Two 60-day trials cut perceived stress versus placebo
In two two-month trials, people who took a standardized ashwagandha extract reported meaningfully less stress than people who took a placebo.
Chandrasekhar 2012 randomized 64 adults with chronic stress to 300 mg of a high-concentration full-spectrum root extract twice daily or placebo for 60 days, and found significant reductions on all stress-assessment scales (P<0.0001). Lopresti 2019 randomized 60 stressed adults to 240 mg/day of a different standardized extract (Shoden) or placebo for 60 days, with a significant Hamilton Anxiety reduction (P=0.04) and a near-significant Depression Anxiety Stress Scale change (P=0.096). Both trials are small, short, and each tests a single proprietary extract; in the Lopresti trial the lead author had prior study funding from a supplement maker.
Who this may not transfer to:Measured in stressed adults of both sexes; the stress result is not specific to one sex.
The studies · 2
Chandrasekhar 2012, Indian J Psychol Med · Indian J Psychol Med
Lopresti 2019, Medicine (Baltimore) · Medicine (Baltimore)
Counts once: this finding and 2 others here come from the same source, so they are one body of evidence, not separate confirmations.
How it works
Morning cortisol fell more on ashwagandha than placebo
Ashwagandha lowered the stress hormone cortisol in the morning more than a placebo did, which points to an effect on the body's central stress axis.
Both trials measured cortisol as a mechanism marker alongside the stress scales. Lopresti 2019 found a significantly greater fall in morning cortisol (P<0.001) and DHEA-S (P=0.004) versus placebo over 60 days at 240 mg/day; Chandrasekhar 2012 found reduced serum cortisol (P=0.0006) at 600 mg/day. The authors read this as a moderating effect on the hypothalamic-pituitary-adrenal axis. Neither abstract reports the absolute change in nanograms, so the size of the drop in everyday terms is not established from these sources.
Who this may not transfer to:Cortisol was measured in adults of both sexes.
The studies · 2
Lopresti 2019, Medicine (Baltimore) · Medicine (Baltimore)
Chandrasekhar 2012, Indian J Psychol Med · Indian J Psychol Med
Counts once: this finding and 2 others here come from the same source, so they are one body of evidence, not separate confirmations.
Mood & stress
Pooled anxiety dropped a large SMD -1.55, but the trials disagreed sharply (I-squared 93.8%)
Pooling the trials, ashwagandha lowered anxiety and stress by a large amount on average, but the trials disagreed with each other so much that the average number carries less weight than its size suggests.
Akhgarjand 2022 pooled randomized trials of ashwagandha for anxiety and stress using a random-effects model. The pooled standardized mean differences were large (anxiety -1.55, stress -1.75), but the heterogeneity statistics were extreme (I-squared above 83% for both), meaning the underlying trials produced widely different results. Extreme heterogeneity plus a small number of short trials of a few proprietary extracts is why the effect is graded emerging rather than moderate: the direction is consistent, the magnitude is not reliable.
Who this may not transfer to:Pooled from trials in adults of both sexes.
The studies · 2
Akhgarjand 2022, Phytother Res · Phytother Res
Chandrasekhar 2012, Indian J Psychol Med · Indian J Psychol Med
Counts once: this finding and 2 others here come from the same source, so they are one body of evidence, not separate confirmations.
Evidence And Methods
Most positive trials are small (under 100 people), short (8 to 12 weeks), and tied to the extract maker
The trials that look good are small, short, and usually tied to the company selling that particular extract. That makes the stress result promising, not proven, and it does not carry across every ashwagandha product on a shelf.
Cheah 2021 (sleep) and Akhgarjand 2022 (anxiety and stress) both note the same structural limits: few trials, small samples, short durations, high heterogeneity, and reliance on branded standardized extracts. A benefit shown for a specific extract at a specific dose does not automatically transfer to a different product with a different withanolide content. This is a statement about the evidence base, not a claim that the effect is absent; larger independent trials would settle the magnitude.
Who this may not transfer to:Describes the randomized-trial literature across both sexes.
The studies · 2
Akhgarjand 2022, Phytother Res · Phytother Res
Cheah 2021, PLoS One · PLoS One
Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.
Sleep
Five trials in 400 adults show a small sleep gain (SMD -0.59)
Across five trials in 400 people, ashwagandha produced a small but consistent improvement in sleep, and the effect was clearest at 600 mg a day for at least eight weeks and in people who actually had insomnia.
Cheah 2021 pooled five randomized controlled trials (400 participants) and found a small significant benefit on overall sleep (standardized mean difference -0.59, 95% CI -0.75 to -0.42), plus improvements in mental alertness on rising and anxiety, but no significant effect on quality of life. The moderate heterogeneity (I-squared 62%) is far lower than the anxiety meta-analysis, which makes the sleep signal steadier. The review notes that long-term safety data are limited.
Who this may not transfer to:Pooled from adults of both sexes, healthy and with insomnia.
The studies · 2
Cheah 2021, PLoS One · PLoS One
Langade 2021, J Ethnopharmacol · J Ethnopharmacol
Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.
People with insomnia fell asleep faster and slept more efficiently on 300 mg twice daily
People with insomnia fell asleep faster and spent more of their time in bed actually asleep on ashwagandha, and they gained more than healthy sleepers did.
Langade 2021 ran a double-blind, randomized, parallel-group trial in both healthy volunteers and insomnia patients taking 300 mg of root extract twice daily. Sleep onset latency and sleep efficiency were the most improved parameters (both P<0.0001 within group), with total sleep time and wake-after-sleep-onset also improving, and the effect was more pronounced in the insomnia group. It is a single small trial and the authors call for larger studies to generalize the result.
Who this may not transfer to:Measured in adults of both sexes, healthy volunteers and insomnia patients.
The study · 1
Langade 2021, J Ethnopharmacol · J Ethnopharmacol
Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.
Muscle And Strength
In 57 untrained young men, bench-press max rose 101 lb (46 kg) versus 57 lb (26 kg) on placebo
Young men new to lifting who took ashwagandha alongside eight weeks of training gained more strength and lost a little more fat than those who trained on a placebo, though it was one small study.
Wankhede 2015 randomized 57 men aged 18 to 50 with little training experience to 300 mg of root extract twice daily or placebo, both groups training for 8 weeks. The ashwagandha group gained more bench-press strength (101 lb (46.0 kg) vs 58 lb (26.4 kg), p=0.001), more leg-extension strength (32 lb (14.5 kg) vs 22 lb (9.8 kg), p=0.04), more arm muscle size, and greater body-fat reduction (p=0.03). It is a single trial in untrained young men using one branded extract, and the effect has not been replicated in women, older adults, or trained lifters.
Who this may not transfer to:Tested only in untrained young men; not shown in women, older adults, or experienced lifters.
The study · 1
Wankhede 2015, J Int Soc Sports Nutr · J Int Soc Sports Nutr
Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.
Progress Markers
Testosterone rose more in training men (+96.2 vs +18.0 ng/dL), not in women
In a couple of small trials in men, testosterone rose a little more on ashwagandha than on a placebo. The effect was not seen in women, and this is early, small evidence rather than a treatment for low testosterone.
Wankhede 2015 found a greater testosterone increase on ashwagandha than placebo in young training men (+96.2 ng/dL vs +18.0, p=0.004). In the mixed-sex Lopresti 2019 stress trial, testosterone rose in males (P=0.038 over time) but not females (P=0.989), and the male change was not significant against placebo (P=0.158). The evidence is a handful of small trials in selected male groups; the size and durability of any effect are not established.
Who this may not transfer to:Testosterone effect seen only in men; no change measured in women.
The studies · 2
Wankhede 2015, J Int Soc Sports Nutr · J Int Soc Sports Nutr
Lopresti 2019, Medicine (Baltimore) · Medicine (Baltimore)
Counts once: this finding and 2 others here come from the same source, so they are one body of evidence, not separate confirmations.
How It Works
The clearest mechanism is the stress axis. Ashwagandha lowers morning cortisol against placebo, and the trials that measured mood and cortisol together point to a moderating action on the hypothalamic-pituitary-adrenal loop, the circuit that governs cortisol.
For sleep, the proposed pathway is activity at GABA, the brain's main calming signal. That fits the mild effect the trials found: people fall asleep somewhat faster, without the heavy sedation of a sleep drug. These are plausible, partly measured mechanisms, not settled ones.
How To Take It
Ways to Do It
If you and, where relevant, the clinician who manages your health decide ashwagandha fits, the practical protocol is short. Read the Cautions section below before you start, because a few situations make it a poor fit. No brand is named here on purpose; the form, the dose, and using it for a defined stretch are what carry the effect.
The human trials used standardized root extract, most often 300 mg twice daily or a single 600 mg dose, and the sleep meta-analysis found the effect clearest at 600 mg a day or more for at least eight weeks. Root extract is the studied form; whole-plant and leaf preparations were not. Because withanolide content varies between products, a third-party-tested extract that states its standardization is the sensible choice.
The trials ran roughly eight to twelve weeks, so that is the window the evidence actually covers. There is no good long-term data yet, so cycling off after a defined stretch keeps you inside the studied range and gives you a natural point to reassess whether it is helping.
Any effect builds over weeks, not in a single dose, so measure it against how you felt before you started. If stress or sleep has not shifted after the studied window, it is not working for you, and there is no case for continuing. Pair it with the practices that have stronger evidence for the same goals, linked below.
Go Deeper
- Anxiety: the condition ashwagandha is most often reached for, with the full range of what helps and how the evidence compares.
- Breath and heart-rate variability: a free, well-evidenced way to act on the same stress axis, with no safety signals to weigh.
- The CBT-I protocol: the first-line, best-evidenced approach to insomnia, the place to start for sleep.
- Resistance training: the loading the strength and testosterone finding was built on, since the trial paired the herb with eight weeks of lifting.
- Testosterone therapy: what actually treats low testosterone, and why a handful of small trials do not make ashwagandha that.
The Chinese Medicine View
Ashwagandha is an Ayurvedic herb, not a Chinese one. It has no entry in the classical Chinese Materia Medica, no assigned channel, temperature, or flavor, and no traditional Chinese indication, because Chinese medicine did not use it. In its own tradition it is a Rasayana, a rejuvenating tonic taken to build strength and resilience over time.
Chinese medicine has its own category for herbs of this kind: the tonifying herbs, the bu herbs, understood to support the body's reserves, and within that the warming Kidney-Yang tonics a practitioner might reach for when someone is depleted and cold. Some modern Western practitioners place ashwagandha alongside those warming tonics by analogy, on the strength of its building, warming reputation in Ayurveda. That is a lens offered to a reader who thinks in the Chinese framework, not a classical designation, because no historical Chinese text describes the herb. Its standing rests on two things held together: centuries of continuous use in Ayurveda as a Rasayana, and the modern trials that point the same way for stress and sleep.
A handful of situations make ashwagandha a poor fit, and one is serious.
Pure, single-ingredient ashwagandha has caused liver injury, and in people who already have liver disease it has been fatal.
Cautions For This Practice
Extra restraintEverything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.
Documented liver injury from pure product, fatal in 3 of 3 with existing liver disease
Bjornsson 2020 described 5 cases from Iceland and the US Drug-Induced Liver Injury Network: jaundice after a 2 to 12 week latency, cholestatic or mixed pattern, prolonged itching and high bilirubin, all self-limited with liver tests normalizing in 1 to 5 months. Philips 2023 reported 23 patients with ashwagandha-associated liver injury in India, of whom 8 took single-ingredient ashwagandha with no adulteration on chemical analysis; 5 had underlying chronic liver disease, 3 developed acute-on-chronic liver failure, and all 3 died. The injury is idiosyncratic and uncommon, but it is real and not explained by contamination. LiverTox, the NIH reference on drug-induced liver injury, carries a dedicated ashwagandha entry.Bjornsson 2020, Liver Int (Iceland and US DILIN case series)Philips 2023, Hepatol Commun (India case series and review)LiverTox: Ashwagandha, NIDDK/NCBI Bookshelf
No more side effects than placebo over 8 to 12 weeks, including thyroid labs
Verma 2021 gave healthy volunteers root extract for 8 weeks and found no significant change or abnormality in vital signs, hematology, biochemistry, or thyroid profile versus placebo, and no reported adverse events. Chandrasekhar 2012 reported adverse effects that were mild and comparable between ashwagandha and placebo. These are the reassuring short-term safety data, but the trials run weeks rather than years and are far too small to detect the rare idiosyncratic liver injury that post-marketing case reports have found.Verma 2021, Complement Ther MedChandrasekhar 2012, Indian J Psychol Med
In 50 hypothyroid patients T3 and T4 rose and TSH fell: a caution if your thyroid is not underactive
Sharma 2018 randomized 50 people with subclinical hypothyroidism to 600 mg/day of root extract or placebo for 8 weeks and found ashwagandha significantly raised T3 and T4 and lowered TSH, effectively normalizing thyroid indices. The direction of this effect depends entirely on the person: welcome in an underactive thyroid, but a thyroid-stimulating activity that can stack with levothyroxine or worsen an overactive thyroid. Larger short trials in healthy people (Verma 2021) found no significant change in thyroid profile, so the effect is clearest where the thyroid is already underactive.Sharma 2018, J Altern Complement Med
Liver injury: avoid it with liver disease, and stop for jaundice, dark urine, or belly pain
Pure, single-ingredient ashwagandha has caused liver injury in independent case series, occasionally severe, and in people who already have liver disease it has been fatal. Do not take it if you have liver disease. If you develop jaundice, dark urine, or abdominal pain while taking it, stop and seek medical care.
Thyroid disease or thyroid medication
Ashwagandha raises thyroid hormone levels. If you have a thyroid condition or take thyroid medication, it can push your levels too high, so raise it with the clinician who manages your thyroid before you start.
Do not take it in pregnancy, and take care around conception and breastfeeding
Ashwagandha is contraindicated in pregnancy. It has a traditional use for bringing on menstruation, and animal studies have linked it to pregnancy loss, so it should be avoided while pregnant and while trying to conceive. There is not enough safety data to support use while breastfeeding, so the cautious course is to avoid it then as well.
Autoimmune disease and immunosuppressant medication
Ashwagandha can stimulate immune activity. That is a reason for care if you have an autoimmune condition such as lupus, rheumatoid arthritis, Hashimoto's thyroiditis, or multiple sclerosis, where added immune stimulation could aggravate the disease, and if you take an immunosuppressant medication, for example after a transplant or for an autoimmune condition, where the herb could work against the drug. Raise it with the clinician managing that condition before starting.
Sedatives, alcohol, and surgery
Its calming effect can add to the effect of sedatives, benzodiazepines, sleep medication, and alcohol, so combining them can leave you more sedated than you intend. Because of that sedative action, stop ashwagandha well before any planned surgery and tell the anesthesiologist you have been taking it.
It is a nightshade
Ashwagandha is in the nightshade family (Solanaceae). Anyone with a known sensitivity or allergy to nightshades may react to it and should approach it accordingly.
Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.
Common Questions
Does ashwagandha actually reduce stress?
In short trials, yes, by a modest amount. Two-month randomized studies found lower stress-scale scores and lower morning cortisol on a standardized extract than on placebo, and a meta-analysis pooled a large average reduction in anxiety and stress. The caution is that the trials are small, short, and mostly test one branded extract, and the pooled anxiety number sits on top of trials that scattered widely. It is a modest short-term effect, best read as promising, and specific to the extracts and doses that were studied.
Is ashwagandha safe because it is natural?
Natural describes where ashwagandha comes from. It says nothing about how the body handles it. Ashwagandha is well tolerated by most people in short trials, with no more side effects than placebo. But independent case series have documented liver injury from pure, uncontaminated single-ingredient product, occasionally severe, and in people with existing liver disease it has been fatal. It also raises thyroid hormones and should be avoided in pregnancy. Those signals are why the Cautions section on this page exists.
How much should I take, and for how long?
The trials used standardized root extract, most often 300 mg twice daily or a single 600 mg dose, for roughly eight to twelve weeks. That window is the extent of what the evidence covers. There is no good long-term data, so cycling off after a defined stretch keeps you inside the studied range. Root extract standardized for withanolides is the studied form; whole-plant and leaf products were not what the trials tested.
Can ashwagandha raise testosterone or build muscle?
The evidence here is early and should not be oversold. In 57 untrained young men, ashwagandha raised bench-press strength and testosterone more than placebo alongside eight weeks of resistance training, and a mixed-sex stress trial saw testosterone rise in men but not women. These are a handful of small studies in selected male groups; the size and durability of any effect are not established, and ashwagandha is not a treatment for low testosterone.
Who should avoid ashwagandha entirely?
Anyone who is pregnant or trying to conceive should avoid it, and so should anyone with liver disease, given the documented liver-injury risk. Anyone who develops jaundice, dark urine, or abdominal pain while taking it should stop and seek medical care. A few more groups should treat it as a decision to make with their clinician:
- People with thyroid disease or on thyroid medication.
- People with autoimmune conditions or on immunosuppressants.
- People taking sedatives, sleep medication, or benzodiazepines.
The full detail for each is in the Cautions section above.
Explore Related
Other pages this one connects to, by the evidence they share, the outcomes they touch, and the ground they cover.
All 20 sources on this page independently checked and cross-referenced.
Thomas Dehli, Founder & Editor, Sacred Lotus
Sacred Lotus has published Chinese medicine reference material since 2001. Integrative pages are held to the same standard as the herb and formula library: cite the source, grade the claim at its real strength, and say where the research has not looked. This page is educational and it is not medical advice. Last reviewed and updated August 9, 2026.
Evidence strength
How confidently the research supports a claim. Strength describes the evidence, not our endorsement.