KSM-66 is a branded ashwagandha extract made only from the root of Withania somnifera, standardized to 5% withanolides measured by HPLC and produced with a water-based process. In human trials it was most often taken at 600 mg per day, split into two 300 mg doses, for about 8 weeks.
That short description packs in several choices that set it apart from other ashwagandha extracts: which part of the plant is used, how much of the plant's chemistry is kept, and which marker compound the dose is built around. Here is what each of those means and what the research behind it looks like.
Key takeaways
- KSM-66 uses root only, not leaf, and is standardized to 5% withanolides by HPLC.
- "Full-spectrum" means the extract aims to keep the root's range of constituents rather than concentrating one compound.
- The most common trial dose was 600 mg per day, given as 300 mg twice daily, in trials lasting about 8 weeks.
- Most ashwagandha trials ran 12 weeks or less, and the NIH says long-term safety is not known. Rare liver injury and thyroid effects have been reported.
What "root-only" and "full-spectrum" mean
Ashwagandha's root and leaf have different chemical compositions, according to the NIH Office of Dietary Supplements. Most supplements use the root, which is also the part used traditionally, but some extracts combine root and leaf. KSM-66 is root only.
"Full-spectrum" is a manufacturing description rather than a regulated term. Its supplier uses it to mean the extract keeps the natural balance of the root's constituents instead of isolating or heavily enriching a single one. That matters because withanolides, the steroidal lactones usually used as the quality marker, are thought to drive many of ashwagandha's effects, yet early research suggests other components may contribute as well.
The strength trial described below states the extract was made with a water-based process using no alcohol or other solvents.
Withanolide standardization, and why the percentage alone misleads
Standardization tells you how much of a marker compound is in each dose, measured by a defined method. KSM-66 is standardized to 5% withanolides by HPLC, so a 300 mg capsule carries about 15 mg of withanolides.
A higher number on another label is not automatically better. Extracts differ in plant part, in which withanolide-type compounds they count, and in how they are measured. The trials summarized by the NIH show how wide the range is:
| Extract type in trial | Plant part | Stated standardization | Daily dose studied |
|---|---|---|---|
| KSM-66 | Root | 5% withanolides | 600 mg |
| Sustained-release root extract | Root | 15 mg withanolides per 300 mg | 300 mg |
| Root and leaf extract (sleep trial) | Root and leaf | 21 mg withanolide glycosides per 60 mg capsule | 120 mg |
| Lower-withanolide extract | Not stated | 1.5% withanolides | 400 mg |
A high-withanolide, root-and-leaf extract is a different ingredient studied at a different dose, not a stronger version of KSM-66. Results from one extract should not be assumed to carry over to another.
The dose and how long trials ran
The research below describes ashwagandha extracts on their own, not any finished MAXIS product.
Strength and recovery. In an eight-week trial, 57 men aged 18 to 50 with little resistance-training experience took 300 mg of KSM-66 twice daily or a starch placebo while following the same program. Bench press one-rep max rose 46.0 kg with ashwagandha versus 26.4 kg with placebo, and leg extension rose 14.5 kg versus 9.8 kg. No serious side effects were reported in either group.
Perceived stress. A 60-day trial in 64 adults with chronic stress used 300 mg of a full-spectrum root extract twice daily and found larger drops in stress-scale scores and serum cortisol than with placebo. A separate eight-week trial in 60 stressed but otherwise healthy adults compared 250 mg and 600 mg per day; both lowered Perceived Stress Scale scores and serum cortisol, with the stronger statistical result at 600 mg.
Sleep. An eight-week trial gave KSM-66 at 600 mg per day to 80 adults, half of them healthy sleepers. Sleep measures improved in both groups, more so in those who started with poor sleep. A 2021 meta-analysis of five trials found a small but significant sleep benefit, larger at 600 mg per day or more and at eight weeks or longer.
Across stress trials, daily doses ranged from about 225 to 1,250 mg of extract over 30 to 90 days, and a 2021 review found larger effects at 500 to 600 mg per day. In short, 600 mg per day for roughly two months is the best-studied pattern for KSM-66, and data beyond 12 weeks are scarce.
Timing and cycling
Most KSM-66 trials split the dose into two capsules a day. None of the trials we reviewed compared morning with evening dosing, so there is no research basis for one time being better. Drowsiness is a reported side effect, which some people factor into when they take it.
Cycling, meaning planned breaks, has not been tested either. What the evidence does say is that ashwagandha appears well tolerated for up to about three months, while its safety over many months or years has not been established. Reviewing your use with a healthcare professional around the three-month mark is a reasonable approach given that gap.
Safety: what is known and what is not
- Long-term use. The NIH notes that evidence on use over many months or years is lacking.
- Common side effects. Usually mild: stomach upset, loose stools, nausea and drowsiness.
- Liver. Liver injury is rare but has been reported, including a case series of five people taking 450 to 1,350 mg per day for one week to four months, who improved after stopping. Product contents were not always verified. Stop and see a doctor if you notice yellowing skin or eyes, dark urine or unusual itching.
- Thyroid. Small studies recorded changes in thyroid hormone levels, and case reports describe excess thyroid hormone. NCCIH advises against use by people with thyroid or autoimmune conditions.
- Pregnancy. Avoid during pregnancy and breastfeeding. Denmark banned ashwagandha in 2023, and France's food safety agency advised against use in pregnancy in 2024, although the evidence behind those decisions is disputed.
- Medications. Possible interactions with thyroid hormone, diabetes and blood pressure medication, immunosuppressants and sedatives. It is not recommended before surgery.
Where MAXIS Ashwagandha+ fits
Ashwagandha+ provides 600 mg KSM-66 ashwagandha root extract per two-capsule serving, the same daily amount used in the trials above. It also contains 400 mg Eury Gold 28 tongkat ali root extract, 200 mg velvet bean seed extract (15% L-Dopa), 50 mg Tribulus terrestris, 50 mg muira puama and 50 mg maca. It helps the body adapt to stress and supports energy and stamina.† It is also available in a stack with Magnesium Glycinate.
It is not for anyone under 18, pregnant or nursing. Check with your doctor first if you have a thyroid, autoimmune or hormone-sensitive condition, or take MAOIs, antipsychotics, Parkinson's, sedative, immunosuppressant or blood pressure medication. Stop two weeks before surgery, and do not combine it with MAXIS Men's Vitality, which also contains ashwagandha.
FAQ
Is KSM-66 the same as regular ashwagandha powder?
No. Plain root powder is ground root, while KSM-66 is an extract standardized to a set withanolide level, so doses are not interchangeable.
Is a higher withanolide percentage better?
Not necessarily. Extracts differ in plant part and in what they measure, and each was studied at its own dose. Match the extract to the research done on it.
How long until people in trials saw changes?
Most of the trials described here measured outcomes at about 8 weeks, and one stress trial at 60 days. Results were not measured beyond those points.
Who should skip it?
Anyone pregnant or breastfeeding, anyone with a thyroid or autoimmune condition, and anyone scheduled for surgery. If you take prescription medication, ask your doctor or pharmacist before starting.
References
- NIH Office of Dietary Supplements (2025). Ashwagandha: Fact Sheet for Health Professionals. ods.od.nih.gov
- National Center for Complementary and Integrative Health (2023). Ashwagandha. nccih.nih.gov
- Wankhede S, Langade D, Joshi K, Sinha SR, Bhattacharyya S (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. PubMed 26609282
- Chandrasekhar K, Kapoor J, Anishetty S (2012). 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 Journal of Psychological Medicine. PubMed 23439798
- Langade D, et al. (2019). Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-blind, Randomized, Placebo-controlled Clinical Study. Cureus. doi:10.7759/cureus.6466
- Langade D, Thakare V, Kanchi S, Kelgane S (2021). Clinical evaluation of the pharmacological impact of ashwagandha root extract on sleep in healthy volunteers and insomnia patients: A double-blind, randomized, parallel-group, placebo-controlled study. Journal of Ethnopharmacology. doi:10.1016/j.jep.2020.113276
- Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R (2021). Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS ONE. doi:10.1371/journal.pone.0257843
†These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
