KSM-66 Ashwagandha: What the Research Says About Stress and Energy

KSM-66 is a standardised root extract of ashwagandha (Withania somnifera), and in small Indian trials it lowered stress scores and morning cortisol, improved some sleep measures and added to strength gains from gym training. The evidence is promising but limited: most studies are short, involve 50 to 150 people, and received the extract from its manufacturer. This guide walks through what each key study found, the doses used, and who should be careful.

What is KSM-66 ashwagandha?

KSM-66 is a trade name for a full-spectrum extract made only from the root of ashwagandha, standardised to contain at least 5% withanolides when measured by HPLC (a laboratory test that checks concentration)². It is produced by one company, Ixoreal Biomed, which also supplied the extract for the trials discussed below²³.

Ashwagandha itself is a small shrub of the nightshade family that grows across the drier parts of India. In Ayurveda it is classed as a Rasayana, a rejuvenating herb, and as Balya, a herb that supports strength. Its roots have traditionally been taken as a powder, often boiled in milk with a little ghee or jaggery.

Why the extract type matters

Not all ashwagandha is the same. The NIH Office of Dietary Supplements notes that trials have used several different preparations, including KSM-66, Sensoril, Shoden and plain root powder, at doses from 240 mg to 1,250 mg of extract a day¹. Some use only the root, others mix root and leaf, and the withanolide content varies widely. A result found with one extract cannot simply be assumed for another, which is why it helps to know exactly what is in your capsule.

Withanolides are a group of naturally occurring steroidal lactones. They are thought to be among the main active compounds, although researchers have not pinned down exactly how ashwagandha works in the body.

What does the research say about KSM-66 and stress?

Two placebo-controlled trials of KSM-66 found lower stress scores and lower blood cortisol after eight weeks or more. A wider review of ashwagandha extracts points the same way, but every study involved small groups of Indian adults.

The 2012 Chandrasekhar trial

In this double-blind trial, 64 adults reporting stress were randomised to 300 mg of KSM-66 twice a day or a placebo for 60 days, and 61 completed it². Scores on the Perceived Stress Scale, a standard 10-question survey, fell by 44.0% in the ashwagandha group compared with 5.5% on placebo. Serum cortisol, a hormone that rises with stress, fell by 27.9% compared with 7.9%. Mild adverse events were reported in both groups at similar rates (6 and 5 people).

The authors list their own limits: a single centre, a modest sample, people with psychiatric or other illness excluded, and a short duration. Baseline stress and cortisol levels were not identical between the groups either.

The 2019 Salve trial: does dose matter?

This trial randomised 60 adults with high stress scores to 250 mg a day, 600 mg a day or placebo for eight weeks; 58 completed it³. Both doses lowered perceived stress more than placebo, but the 600 mg group showed the clearer change. Average serum cortisol fell from 16.12 to 10.86 mcg/dL on 600 mg, compared with 16.15 to 15.52 mcg/dL on placebo. Anxiety scores improved significantly only at 600 mg. No adverse events were reported.

How to read these numbers

A fall in a questionnaire score is not the same as feeling transformed. Stress scales measure how often people feel overwhelmed or unable to cope, and a lower score means fewer such days. It is also worth noticing that the placebo groups improved too, which is normal in stress research: simply joining a study, being checked on and paying attention to your routine helps. The fair comparison is always the gap between the ashwagandha and placebo groups, not the change from the start. In both KSM-66 stress trials that gap was meaningful, but it came from groups of 20 to 32 people, so the true effect in the wider population could be smaller.

What the broader evidence shows

A 2021 systematic review summarised by the NIH Office of Dietary Supplements pooled seven studies with 491 adults, all from India, lasting six to eight weeks¹. Three used KSM-66. Benefits for stress and anxiety appeared greater at 500 to 600 mg a day than at lower doses. The US National Center for Complementary and Integrative Health sums it up plainly: some ashwagandha preparations may help with stress and insomnia, but evidence on anxiety is unclear⁷.

Does KSM-66 help with energy, sleep and strength?

No trial has measured "energy" directly as its main outcome for KSM-66. The closest evidence comes from studies on sleep and on strength training, plus the stress findings above, since poor sleep and constant stress are two of the most common reasons people feel drained.

Sleep

A 2019 trial gave 60 adults with insomnia either 300 mg of KSM-66 twice daily, taken with milk or water, or a placebo for ten weeks⁴. Time taken to fall asleep, measured with a wrist activity monitor, fell from about 41.6 to 29.0 minutes, compared with 42.0 to 34.0 minutes on placebo. Sleep efficiency and sleep quality scores also improved more than placebo. Total sleep time and night-time waking did not differ significantly, which is an important nuance.

A 2021 meta-analysis in PLOS ONE pooled five randomised trials, four of them using KSM-66⁵. It found a small but significant benefit for overall sleep. Effects were larger in people with insomnia, at doses of 600 mg a day or more, and when the supplement was taken for eight weeks or longer. The authors noted that more safety data are needed before long-term use can be judged.

Strength and recovery

In a 2015 trial, 57 young men new to weight training were randomised to 300 mg of KSM-66 twice daily or a placebo for eight weeks while following the same gym programme; 50 completed it⁶. Bench-press strength rose by an average of 46.0 kg compared with 26.4 kg on placebo, and leg-extension strength by 14.5 kg compared with 9.8 kg. Arm and chest muscle size increased more than with placebo, while thigh muscle size did not differ significantly. The participants were healthy, untrained and mostly in their late twenties, so the results may not apply to older men or experienced lifters.

KSM-66 trials at a glance

The table below lists the main KSM-66 studies discussed here, with who took part, what they took and the key caveat for each.

How strong is the evidence for KSM-66?

The evidence is encouraging but early. It rests on a handful of short, small trials, nearly all run in India, and the extract was supplied by its manufacturer in each of the studies above.

• Small samples. Most trials enrolled 50 to 65 people, split into two or three groups. Small studies can overstate effects.
• Short duration. Studies ran for 8 to 12 weeks. Nobody knows what happens over years of use.
• Narrow populations. Participants were usually healthy adults without other illnesses, and few were over 60.
• Industry links. The papers declare no conflicts of interest, but they acknowledge that the extract was provided by Ixoreal Biomed²⁶. That does not make the results wrong, but independent replication matters.
• Inconsistencies in reporting. Some papers report slightly different figures in the abstract and the results sections, a sign that the data deserve careful reading.

None of this means KSM-66 does nothing. It means the honest summary is "may help some adults with stress and sleep over a couple of months", not "proven to boost energy". Anyone who claims more is going beyond the data.

It also helps to be clear about what the studies did not test. None compared KSM-66 with lifestyle measures such as regular exercise or better sleep habits, and none looked at people whose tiredness came from an underlying illness. If you feel worn out most days, the research on ashwagandha is not a reason to skip a check-up; our guide to everyday habits that drain men's energy covers the basics worth fixing first.

How much KSM-66 was used in studies, and how is it taken?

The most common research dose was 600 mg a day, taken as one 300 mg capsule twice daily, for at least eight weeks. One trial tested 250 mg a day and found smaller effects³.

In practice, most people take ashwagandha after meals to reduce the chance of an upset stomach. The insomnia trial allowed participants to take it with milk or water⁴, which fits the traditional Indian practice of taking the root with warm milk. Consistency matters more than the exact hour; our article on the best time to take ashwagandha and shilajit goes into morning versus night routines in more detail.

• Follow the dose printed on your product rather than a study dose.
• Give it a fair, regular trial while keeping an eye on how you feel.
• Do not double up products that both contain ashwagandha.
• Stop and see a doctor if you notice yellow eyes, dark urine, itching or a racing heart.

If you are comparing ashwagandha with other Ayurvedic tonics, our explainer on shilajit versus ashwagandha covers how the two differ.

Who should avoid KSM-66 ashwagandha?

Ashwagandha is generally well tolerated for up to about three months, but it is not suitable for everyone, and long-term safety is unknown¹. Common mild effects include stomach upset, loose stools, nausea and drowsiness.

Rare but serious liver injury has been linked to ashwagandha products. The NIH LiverTox database rates ashwagandha as a likely cause of clinically apparent liver injury, usually appearing 2 to 12 weeks after starting and mostly resolving after stopping⁸. Ashwagandha may also raise thyroid hormone levels, and cases of an overactive thyroid have been reported¹.

Speak to a doctor before using ashwagandha if any of the following apply to you¹⁷:

• You are pregnant, trying to conceive or breastfeeding.
• You have a thyroid disorder or take thyroid medicine.
• You have an autoimmune condition or take immunosuppressants.
• You take medicines for diabetes, blood pressure, seizures, sleep or anxiety.
• You have liver disease or a hormone-sensitive prostate cancer.
• You have surgery planned.

Our full guide to ashwagandha side effects and who should avoid it covers each of these in detail.

A doctor can arrange simple blood tests, such as haemoglobin, thyroid function, blood sugar, vitamin B12 and vitamin D, which explain a large share of persistent tiredness. You can also book a free consultation with our Ayurveda team to talk through your routine.

The bottom line

KSM-66 is one of the best-studied ashwagandha extracts, and small trials suggest it may help adults feel less stressed and sleep a little better over two to three months. The evidence is still early, mostly industry-supplied and short-term, so treat it as one part of a routine built on sleep, food and movement, and check with a doctor if you have a medical condition or take regular medicines. You can explore our men's wellness range once those basics are in place.

Sources

1. NIH Office of Dietary Supplements: Ashwagandha: Is it helpful for stress, anxiety, or sleep? Health Professional Fact Sheet (2025)
2. Indian Journal of Psychological Medicine: Chandrasekhar K et al. 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 (2012)
3. Cureus: Salve J et al. Adaptogenic and anxiolytic effects of ashwagandha root extract in healthy adults: a double-blind, randomized, placebo-controlled clinical study (2019)
4. Cureus: Langade D et al. Efficacy and safety of ashwagandha (Withania somnifera) root extract in insomnia and anxiety: a double-blind, randomized, placebo-controlled study (2019)
5. PLOS ONE: Cheah KL et al. Effect of Ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis (2021)
6. Journal of the International Society of Sports Nutrition: Wankhede S et al. Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial (2015)
7. NIH National Center for Complementary and Integrative Health: Ashwagandha: Usefulness and Safety (2023)
8. NIH LiverTox: Ashwagandha (2024)