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KSM-66®

Withania somnifera
Evidence Level
Strong
7 Clinical Trials
6 Documented Benefits
4/5 Evidence Score

KSM-66 is the most extensively studied branded ashwagandha (Withania somnifera) extract, made by Ixoreal Biomed. It is a full-spectrum, root-only extract produced with a proprietary water-based process that uses no alcohol or harsh solvents, which preserves the natural balance of the root's compounds while standardizing it to at least 5% withanolides. Backed by more than 20 human clinical trials, it is the form behind much of the modern ashwagandha research. As an adaptogen, it is used to help the body manage stress and support a calmer mood, better sleep, healthy cortisol balance, strength and exercise recovery, memory and focus, and, in men, healthy testosterone and reproductive health. Most studies use 300 mg twice daily.

Studied Dose 600 mg/day, commonly split as 300 mg twice daily, of standardized root extract
Active Compound Withanolides (≥5%)

Benefits

Stress and Cortisol Balance

Helps the body adapt to stress and supports healthy cortisol levels. At 300 mg twice daily it has reduced perceived stress scores and lowered elevated cortisol versus placebo in chronically stressed adults.

Supported by Trial 1

Anxiety and Mood

Supports a calmer, more balanced mood and eases day-to-day anxiety. Studied at 300-600 mg of root extract daily over about 8 weeks, with the largest changes in people under ongoing stress.

Supported by Trial 1, Trial 5

Sleep Quality

Supports better sleep quality and faster sleep onset, especially with an evening dose, by helping calm a cortisol-driven stress response. Benefits build gradually over weeks of daily use rather than acting as a sedative.

Supported by Trial 3, Trial 6

Memory and Focus

Supports memory, attention, and focus, including under stress. Studied for improvements in working memory, executive function, and reaction time in adults.

Supported by Trial 2

Strength, Endurance, and Recovery

Supports muscle strength, size, and exercise recovery alongside resistance training, and has improved cardiorespiratory endurance (VO2 max) in healthy active adults at 600 mg per day.

Supported by Trial 4

Testosterone and Male Fertility

May support healthy testosterone levels and male reproductive health. In men, including those with low sperm counts, it has been studied for improvements in testosterone, sperm count, and sperm motility.

Supported by Trial 5

Mechanism of action

1

Stress and Anxiety Reduction

KSM-66 reduces cortisol production by modulating the hypothalamic-pituitary-adrenal (HPA) axis, calming the stress response. Its withanolides also enhance GABA receptor activity, promoting relaxation and reducing anxiety.

2

Cognitive Enhancement

KSM-66 increases acetylcholine levels and supports neuronal signaling by inhibiting acetylcholinesterase, enhancing memory and focus. It also reduces oxidative stress in the brain, protecting neurons and supporting synaptic plasticity.

3

Improved Sleep Quality

KSM-66 promotes GABAergic activity, calming neural excitability to facilitate faster sleep onset and deeper rest. Its stress-reducing effects further support sleep by lowering cortisol-driven arousal.

4

Enhanced Physical Performance

KSM-66 improves mitochondrial energy production and oxygen utilization, boosting endurance and strength. It also reduces exercise-induced muscle damage by lowering oxidative stress and inflammation.

5

Testosterone and Fertility Support

KSM-66 upregulates steroidogenic enzymes and balances reproductive hormones, increasing testosterone and sperm quality. Its antioxidant properties protect testicular cells, enhancing male fertility.

6

Immune System Support

KSM-66 enhances immune function by increasing natural killer cell activity and cytokine production. Its adaptogenic effects reduce stress-related immune suppression, bolstering overall resilience.

Clinical trials

1
KSM-66® for Stress Reduction — Chronic Stress Clinical Trial

Prospective, randomized, double-blind, placebo-controlled study of KSM-66 ashwagandha root extract (300 mg twice daily, 600 mg/day) vs placebo in 64 chronically stressed adults for 60 days. Outcomes: Perceived Stress Scale (PSS), DASS-21, serum cortisol, safety. (Indian J Psychol Med)

64 chronically stressed adults. 60-day intervention.

KSM-66® significantly reduced PSS scores (44% reduction vs placebo), DASS-21 anxiety/depression/stress subscales, and serum cortisol (~28% reduction vs placebo). Generally well-tolerated. Critical context: this is the foundational stress trial heavily cited in ashwagandha marketing. Industry-funded (Ixoreal Biomed). Independent replication has been broadly supportive but with smaller effect sizes.

2
KSM-66® for Memory and Cognitive Function — Clinical Trial

Randomized, double-blind, placebo-controlled trial of KSM-66 ashwagandha (600 mg/day) vs placebo in 50 healthy adults with mild memory complaints for 8 weeks. Outcomes: cognitive performance battery (CANTAB-equivalent), memory scores. (J Diet Suppl)

50 healthy adults with subjective memory concerns. 8-week intervention.

KSM-66 significantly improved working memory, attention, executive function, and information processing speed vs placebo. Cognitive effects emerged at 4 and 8 weeks. Industry-funded; effect sizes reasonable. Adds to evidence for ashwagandha's cognitive applications.

3
KSM-66® for Sleep Quality — Evidence Synthesis

Evidence review and pooled analysis examining ashwagandha (multiple branded extracts including KSM-66, Shoden) effects on sleep quality. (PLoS One)

Pooled across multiple ashwagandha sleep clinical trials.

Ashwagandha extracts (including KSM-66) significantly improved sleep quality measures (PSQI), sleep latency, and total sleep time vs placebo. Effects most pronounced in adults with insomnia or sleep disturbances. Effect sizes modest to moderate. Provides reasonable evidence for sleep applications, with multiple consistent trials.

4
KSM-66® for Cardiorespiratory Endurance and Recovery — Clinical Trial

Randomized, double-blind, placebo-controlled trial of KSM-66 (600 mg/day) vs placebo in 50 healthy athletic adults for 8 weeks. Outcomes: VO2max, recovery markers, cardiorespiratory fitness. (Ayu)

50 healthy athletic adults. 8-week intervention.

KSM-66 increased VO2max ~13.6% vs placebo and improved recovery markers. Industry-funded. Note: VO2max improvements of this magnitude with a botanical supplement are substantial — would warrant rigorous independent replication. Most ashwagandha 'performance' marketing rests on this and similar small industry-funded trials.

5
KSM-66® for Male Fertility — Oligospermic Men Clinical Trial

Randomized, double-blind, placebo-controlled trial of KSM-66 (600 mg/day, sometimes 5 g of root) vs placebo in 75 oligospermic infertile men for 12 weeks. Outcomes: sperm count, sperm motility, sperm morphology, serum testosterone, LH, FSH. (Evid Based Complement Alternat Med)

75 oligospermic infertile men. 12-week intervention.

KSM-66 significantly increased sperm count (167% improvement), sperm motility (57% improvement), and serum testosterone (17% increase) vs placebo. Industry-funded. Note: effect sizes large; specific to oligospermic infertile population — extrapolation to general male testosterone enhancement is less supported.

6
KSM-66® for Sexual Function in Healthy Women — Clinical Trial

Randomized, double-blind, placebo-controlled trial of KSM-66 ashwagandha (600 mg/day) vs placebo in 50 women with self-reported low sexual function for 8 weeks. Outcomes: Female Sexual Function Index (FSFI), sexual satisfaction. (Biomed Res Int — or, Health Sci Rep)

50 women with low sexual function. 8-week intervention.

KSM-66 significantly improved FSFI total score, arousal, lubrication, orgasm, and sexual satisfaction vs placebo. Industry-funded. Effects attributed to stress reduction and HPA axis modulation rather than direct hormonal effects. Adds to KSM-66's broader stress/hormonal applications.

7
KSM-66® Safety Assessment — Genotoxicity and Tolerability

Comprehensive safety assessment of KSM-66 standardized ashwagandha root extract through battery of genotoxicity, acute and subchronic toxicity tests, plus human tolerability study. (Cureus or related Ixoreal safety publications)

Battery of toxicology + human tolerability.

KSM-66 showed no significant adverse effects on hematological, liver, kidney, or thyroid markers in human tolerability assessment. Generally well-tolerated. Contradictory evidence: separate case reports have linked ashwagandha (multiple extracts, not specifically KSM-66) to acute hepatotoxicity (report; LiverTox database lists ashwagandha as established cause of drug-induced liver injury). The discrepancy suggests rare idiosyncratic hepatotoxicity may occur despite generally good tolerance — discontinue with any hepatic warning signs.

Side effects and drug interactions

Common Potential side effects

Gastrointestinal discomfort: mild stomach upset, nausea, or loose stools can occur, more likely at higher doses or on an empty stomach.
Drowsiness: its calming effect can cause mild sleepiness, especially at higher doses or when combined with sedatives.
Headache: a small number of people report mild headaches, which are often dose-related.
Allergic reactions: rarely, skin rash or itching can occur in people sensitive to ashwagandha, which is a nightshade-family plant.
Lowered blood pressure: may modestly lower blood pressure, which can cause lightheadedness in people who already run low or take blood-pressure medication.
Thyroid and hormonal effects: can raise thyroid hormone levels, so use caution with thyroid conditions or medication; it is not recommended during pregnancy.

Important Drug interactions

Sedatives and CNS depressants (benzodiazepines, sleep medications, alcohol): may add to their calming, sedative effect.
Thyroid medication (levothyroxine): ashwagandha can raise thyroid hormone levels and may add to thyroid medication, so monitor thyroid labs.
Immunosuppressants: its immune-stimulating activity may work against drugs meant to suppress the immune system, such as after a transplant or for autoimmune disease.
Blood pressure and diabetes medication: may add to the effects of antihypertensive and blood-sugar-lowering drugs.
Other sedative or thyroid-active supplements: effects may be additive; combine with care.

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Anxiety→Fertility→Immune Support→Low Testosterone→Sleep & Insomnia→Stress & High Cortisol→Thyroid Support→

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Frequently asked questions about KSM-66®

What makes KSM-66 different from regular ashwagandha?

KSM-66 is a branded, standardized full-spectrum ashwagandha root extract made by Ixoreal Biomed using a proprietary water-based process that avoids alcohol and harsh solvents. It is standardized to at least 5% withanolides and is the most clinically studied ashwagandha, so when research refers to a specific branded extract it is often KSM-66. Generic ashwagandha can vary widely in potency and quality, whereas a branded, standardized extract is more consistent from batch to batch.

Is KSM-66 better than Sensoril or Shoden?

They are different standardized ashwagandha extracts with different profiles. KSM-66 is a root-only, full-spectrum extract standardized to about 5% withanolides and has the largest body of research, spanning stress, sleep, strength, and testosterone. Sensoril uses root and leaf and is standardized to a higher withanolide level, and Shoden is a high-withanolide extract often studied for sleep. The best choice depends on your goal; KSM-66 is the most broadly studied.

Should I take KSM-66 in the morning or at night?

Either works, and it depends on your goal. For daytime stress and focus, a morning or split dose (such as 300 mg twice daily) is common. For sleep, an evening dose is often preferred. Because it works gradually by retuning the stress response rather than acting as a fast sedative, daily consistency matters more than the exact time.

What is KSM-66?

KSM-66 is the most extensively studied branded ashwagandha (Withania somnifera) extract, made by Ixoreal Biomed. It is a full-spectrum, root-only extract produced with a proprietary water-based process that uses no alcohol or harsh solvents, which preserves the natural balance of the root's compounds while standardizin…

What is KSM-66 used for?

KSM-66 is researched primarily for Cognitive, Athletic Performance, and Sleep Health. Helps the body adapt to stress and supports healthy cortisol levels. At 300 mg twice daily it has reduced perceived stress scores and lowered elevated cortisol versus placebo in chronically stressed adults.

What is the recommended dosage of KSM-66?

The clinically studied dose is 600 mg/day, commonly split as 300 mg twice daily, of standardized root extract Always follow the product label and check with a healthcare provider for personal advice.

Is KSM-66 safe, and does it have side effects?

For most healthy adults, KSM-66 is well tolerated at studied doses. Reported effects can include: Gastrointestinal discomfort: mild stomach upset, nausea, or loose stools can occur, more likely at higher doses or on an empty stomach. Drowsiness: its calming effect can cause mild sleepiness, especially at higher doses or when combined with sedatives. It may also interact with some medications. KSM-66 is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does KSM-66 interact with any medications?

Possible interactions include: Sedatives and CNS depressants (benzodiazepines, sleep medications, alcohol): may add to their calming, sedative effect. Thyroid medication (levothyroxine): ashwagandha can raise thyroid hormone levels and may add to thyroid medication, so monitor thyroid labs. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for KSM-66?

NutraSmarts rates the evidence for KSM-66 as Strong (4 out of 5). It is backed by 7 clinical trials and 8 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(8 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Wankhede S, Langade D, Joshi K, Sinha SR, Bhattacharyya S Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. Journal of the International Society of Sports Nutrition. 2015;12:43. doi: 10.1186/s12970-015-0104-9.PubMedUsed to support: Brand-specific (KSM-66) RCT reporting greater gains in muscle strength, size, recovery and testosterone in resistance-trained men. Honest framing: a small single-site trial conducted with the manufacturer's branded extract; effect sizes warrant cautious interpretation.
  2. 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. doi: 10.7759/cureus.6466.PubMedUsed to support: A KSM-66 RCT reporting reduced stress and serum cortisol and improved well-being. Honest framing: small sample and manufacturer-affiliated authorship; results are promising but not definitive.
  3. Sharma AK, Basu I, Singh S Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. J Altern Complement Med. 2018;24(3):243-248. doi: 10.1089/acm.2017.0183.PubMedUsed to support: A KSM-66 RCT in subclinical hypothyroidism reporting normalized TSH and increased T3/T4 over 8 weeks. Honest framing: a small single-center trial using the manufacturer's branded extract; suggestive for thyroid support but needs independent replication and is not a treatment for overt thyroid disease.
  4. Choudhary D, Bhattacharyya S, Bose S Efficacy and Safety of Ashwagandha (Withania somnifera (L.) Dunal) Root Extract in Improving Memory and Cognitive Functions. Journal of Dietary Supplements. 2017;14(6):599-612. doi: 10.1080/19390211.2017.1284970.PubMedUsed to support: A KSM-66 RCT reporting improved memory and executive function in adults with mild cognitive impairment. Honest framing: small pilot-scale trial with manufacturer involvement; cognitive claims need independent replication.
  5. 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):255-62. doi: 10.4103/0253-7176.106022.PubMedUsed to support: The foundational KSM-66 stress trial: 300 mg of root extract twice daily for 60 days significantly reduced perceived stress and serum cortisol versus placebo in chronically stressed adults. Anchors the stress and cortisol-balance use.
  6. Choudhary B, Shetty A, Langade DG. Efficacy of Ashwagandha (Withania somnifera [L.] Dunal) in improving cardiorespiratory endurance in healthy athletic adults. Ayu. 2015;36(1):63-8. doi: 10.4103/0974-8520.169002.PubMedUsed to support: Randomized placebo-controlled trial in which KSM-66 (600 mg/day) improved cardiorespiratory endurance (VO2 max) in healthy athletic adults. Supports the endurance and physical-performance use; industry-funded.
  7. Dongre S, Langade D, Bhattacharyya S. Efficacy and Safety of Ashwagandha (Withania somnifera) Root Extract in Improving Sexual Function in Women: A Pilot Study. Biomed Res Int. 2015;2015:284154. doi: 10.1155/2015/284154.PubMedUsed to support: Randomized placebo-controlled trial in which KSM-66 root extract improved female sexual function scores (FSFI) in healthy women. One of the few ashwagandha trials in women's sexual health.
  8. Ambiye VR, Langade D, Dongre S, Aptikar P, Kulkarni M, Dongre A. 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. doi: 10.1155/2013/571420.PubMedUsed to support: Clinical trial of ashwagandha root extract in oligospermic (low sperm count) men, reporting improvements in sperm count, motility, and testosterone. Supports the male fertility and testosterone use.