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Ashwagandha KSM-66
Also known as KSM-66 Ashwagandha
Full-spectrum ashwagandha root extract standardised for withanolide content using a low-temperature aqueous extraction process; the most heavily trialled ashwagandha formulation for cortisol reduction and stress resilience.
Reported side effects:Loose stoolsNauseaDrowsiness
Be careful if: pregnant, breastfeeding, some medical situations
Suspect a side effect? Report it to the MHRA Yellow Card scheme ↗
3linked conditions
21linked studies
Evidence
What the research actually shows
We link to relevant studies and leave interpretation to you and your healthcare professional.
Safety
Safety and considerations
What sources report about side effects, who should be careful, and medicines to ask about first.
Reported side effects
| Reported effect | How often | Basis | Sources |
|---|---|---|---|
| Loose stools | common | Listed by NIH ODS fact sheets | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07) |
| Nausea | common | Listed by NIH ODS fact sheets | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07) |
| Drowsiness | common | Listed by NIH ODS fact sheets | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07) |
Serious effects reported
| Reported effect | How often | Basis | Sources |
|---|---|---|---|
| Adverse effects on liver function (a few reports) — evidence base is whole-plant ashwagandha (NIH ODS), cross-referenced from the parent ashwagandha profile; no liver cases reported in the KSM-66 trials reviewed | unknown | Listed by NIH ODS fact sheets | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07)Jillella A, Keerthi N, Venkateswar Reddy J. Efficacy and Safety of Ashwagandha Root Extract Capsule (KSM-66) on Skin and Hair Health in Healthy Adults: RCT. Phytother Res 2026;40(8):4946-4959 (PMID 41770039) |
Be careful if you…
| Applies to | What sources say | Sources |
|---|---|---|
| pregnant | Some experts advise against the use of ashwagandha by women who are pregnant (NIH ODS; whole-plant evidence base cross-referenced for this root extract). | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07) |
| breastfeeding | No breastfeeding-specific guidance found in the sources checked (NIH ODS ashwagandha fact sheet has no lactation statement); the KSM-66 trials reviewed enrolled neither pregnant nor breastfeeding participants. | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07)Jillella A, Keerthi N, Venkateswar Reddy J. Efficacy and Safety of Ashwagandha Root Extract Capsule (KSM-66) on Skin and Hair Health in Healthy Adults: RCT. Phytother Res 2026;40(8):4946-4959 (PMID 41770039) |
| some medical situations | Ashwagandha might affect thyroid function and interact with some medicines; people with thyroid conditions or on regular medication should ask a clinician before use (NIH ODS). | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07) |
| some medical situations | Some experts advise against use by men with hormone-sensitive prostate cancer (NIH ODS). | Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07) |
How much is too much
Sources
Ashwagandha (NIH ODS fact sheet, Health Professional edition; retrieved via Internet Archive snapshot 2026-10-07)Jillella A, Keerthi N, Venkateswar Reddy J. Efficacy and Safety of Ashwagandha Root Extract Capsule (KSM-66) on Skin and Hair Health in Healthy Adults: RCT. Phytother Res 2026;40(8):4946-4959 (PMID 41770039)
Suggested uses (unproven)
Where people report using it and what trials suggest
- Moderate evidenceStress/cortisol reduction (KSM-66 specific RCTs)
- Moderate evidenceSleep quality
- Weak evidenceSmall testosterone rise in stressed/infertile men
Where the evidence is negative
Common claims the trials do not support
- Testosterone effects in healthy trained men are inconsistent and clinically small.
- No meaningful evidence for 'testosterone booster' marketing in eugonadal men.
- Same rare hepatotoxicity/thyroid signals as generic ashwagandha.
Standardised full-spectrum ashwagandha extract (KSM-66) used in most cited stress/sports RCTs; same evidence base and caveats as ashwagandha generally.
Evidence grades reflect study quality and consistency, not marketing claims.
21studies referenced
19journals
2015–2026publication range
Ordered by strength of evidence, then result direction.
01Do "testosterone boosters" really increase serum total testosterone? A systematic reviewMorgado A, et al. · International journal of impotence research · 2024PMID 37697053 ↗02Effects of Ashwagandha (Withania Somnifera) on stress and anxiety: A systematic review and meta-analysisArumugam V, et al. · Explore (New York, N.Y.) · 2024PMID 39348746 ↗03Plant-derived nootropics and human cognition: A systematic reviewLorca C, et al. · Critical reviews in food science and nutrition · 2023PMID 34978226 ↗04Clinician guidelines for the treatment of psychiatric disorders with nutraceuticals and phytoceuticals: The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) TaskforceSarris J, et al. · The world journal of biological psychiatry : the official journal of the World Federation of Societies of Biological Psychiatry · 2022PMID 35311615 ↗05Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trialsAkhgarjand C, et al. · Phytotherapy research : PTR · 2022PMID 36017529 ↗06Examining the Effects of Herbs on Testosterone Concentrations in Men: A Systematic ReviewSmith SJ, et al. · Advances in nutrition (Bethesda, Md.) · 2021PMID 33150931 ↗Show all 21 studies
07Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysisCheah KL, et al. · PloS one · 2021PMID 34559859 ↗08Exploring 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 trialSmith SJ, et al. · Journal of psychopharmacology (Oxford, England) · 2023PMID 37740662 ↗09Effect of an ashwagandha (Withania Somnifera) root extract on climacteric symptoms in women during perimenopause: A randomized, double-blind, placebo-controlled studyGopal S, et al. · The journal of obstetrics and gynaecology research · 2021PMID 34553463 ↗10A Randomized, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha ( Withania somnifera) in Aging, Overweight MalesLopresti AL, et al. · American journal of men's health · 2019PMID 30854916 ↗11An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled studyLopresti AL, et al. · Medicine · 2019PMID 31517876 ↗12Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trialWankhede S, et al. · Journal of the International Society of Sports Nutrition · 2015PMID 26609282 ↗13Safety of 12-Months Administration of Ashwagandha ( Withania somnifera ) Standardized Root Extract in Healthy Adults: A Prospective, Observational StudySalve J, et al. · Phytotherapy research : PTR · 2026PMID 41063394 ↗14Evaluation of Potential Hormonal Activities of Ashwagandha (Withania somnifera)Vollmer G, et al. · Phytotherapy research : PTR · 2026PMID 41454558 ↗15Efficacy and safety of Ashwagandha (Withania somnifera) root extract in pregnant women: a prospective, randomized, comparative, open-label, 12-week studyAjgaonkar A, et al. · Frontiers in global women's health · 2026PMID 41767760 ↗16Withania somnifera and Trigonella foenum-graecum as ingredients of testosterone-boosting supplements: Possible clinical implicationsSkrzypiec-Spring M, et al. · Advances in clinical and experimental medicine : official organ Wroclaw Medical University · 2025PMID 38628109 ↗17The benefits of ashwagandha (Withania somnifera) supplements on brain function and sports performanceGuo S, et al. · Frontiers in nutrition · 2024PMID 39155932 ↗18Can Ashwagandha Benefit the Endocrine System?-A ReviewWiciński M, et al. · International journal of molecular sciences · 2023PMID 38003702 ↗19Pharmacological evaluation of Ashwagandha highlighting its healthcare claims, safety, and toxicity aspectsMandlik Ingawale DS, et al. · Journal of dietary supplements · 2021PMID 32242751 ↗20Effects of Withania somnifera (Ashwagandha) on Stress and the Stress- Related Neuropsychiatric Disorders Anxiety, Depression, and InsomniaSpeers AB, et al. · Current neuropharmacology · 2021PMID 34254920 ↗21Neuroprotective effects of Withania somnifera in the SH-SY5Y Parkinson cell modelWongtrakul J, et al. · Heliyon · 2021PMID 34765761 ↗
Published research summaries are unavailable.
Outcomes & conditions
Outcomes & conditions →Why people look into Ashwagandha KSM-66 — and what they report
Associated conditions and community-reported outcomes, wrapped together on one page. Aggregates appear only once enough reports arrive.
Important: This page reflects observational, aggregate-only community reporting and independent published research. It is not medical advice, and it does not claim any compound treats, cures, or is effective for any condition. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or treatment.
Availability
Where to get Ashwagandha KSM-66 (UK)
How this compound is sold in the UK, and where our readers typically find it.
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