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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Ashwagandha

Withania somnifera (KSM-66, Sensoril)

Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.

The written rationale for this grade is still being prepared.

FDA
Not FDA evaluated (dietary supplement)

Reference only. Not medical advice.

What can go wrong

Generally well tolerated. Rare reports of liver injury exist (often linked to high doses or adulterated products). Possible thyroid-hormone elevation makes caution warranted in hyperthyroidism or with thyroid medication. As an immunomodulator it is cautioned in autoimmune disease, and it is not recommended in pregnancy. Quality and adulteration vary widely across brands.

This is something to take to a clinician. The Atlas can tell you what is known about ashwagandha in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.

An Ayurvedic adaptogen standardized to withanolide content (KSM-66 and Sensoril are the dominant research extracts). Among testosterone supplements it carries some of the more credible human data, though many trials are funded by or linked to extract manufacturers, so independent replication is still limited. The documented testosterone effect is real but modest (roughly 10-22%), and is largest in stressed, subfertile, or previously untrained men rather than in already-optimized eugonadal men.

The adaptogen with the strongest supplement evidence base for testosterone.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Stress and anxiety reduction (cortisol-mediated)
  • Reported testosterone support in stressed men
  • Resistance-training recovery
  • Sleep quality

How it is supposed to work

Withanolides appear to act primarily on the HPA axis, blunting cortisol output. Because cortisol and testosterone are reciprocally related, lowering chronically elevated cortisol can indirectly support testosterone and LH/FSH signaling. The herb does not appear to be a direct androgen or aromatase modulator at studied doses.

The catch the marketing skips

The testosterone benefit is largely a downstream effect of stress reduction. In men who are not stressed or cortisol-elevated, the effect on testosterone shrinks markedly. The headline percentages come from stressed or subfertile cohorts, not healthy eugonadal men.

What people get wrong

  • Often saidAshwagandha raises testosterone by 50%

    ActuallyFalse. The documented increase is roughly 10-22%, and that magnitude is seen mainly in men with elevated stress/cortisol or subfertility. In eugonadal, low-stress men the effect is smaller and inconsistent.

  • Often saidAny ashwagandha product gives the studied benefit

    ActuallyThe trials used standardized extracts (KSM-66, Sensoril) at specific doses. Generic, unstandardized powders may not match the studied withanolide content.

Who profits, and who pushes back

  • Andrew Huberman

    Promotes itHuge (podcast)

    Has discussed ashwagandha favorably on his podcast while also noting cortisol-related cautions; not a documented brand spokesperson for ashwagandha specifically

  • Supplement-aisle and fitness influencers

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itBroad

    Many promote standardized-extract brands under affiliate or sponsorship arrangements

How we got here

Ashwagandha is one of the oldest documented herbs in Ayurvedic medicine, referenced in both the Charaka Samhita and Sushruta Samhita over 3,000 years ago. Its Sanskrit name translates roughly to 'smell of horse,' connoting the strength and vitality it was believed to confer. It was classified as a rasayana (rejuvenative tonic). Western interest accelerated in the 2010s once standardized extracts enabled reproducible clinical trials.

  1. ~1000 BCEDocumented in classical Ayurvedic texts
  2. 2009KSM-66 standardized extract commercialized by Ixoreal
  3. 2015Wankhede RCT popularizes testosterone claim
  4. 2018-2024Becomes a mass-market supplement-aisle staple

At a glance

Tradition
Ayurveda, 3000+ years
Active class
Withanolides (steroidal lactones)
Lead extracts
KSM-66, Sensoril
Typical dose
300-600 mg/day

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Ashwagandha. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.
  • Where we land. We have not taken a position on this yet.

Sources

The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.

The studies that matter

  • Wankhede et al. (KSM-66)2015

    300 mg KSM-66 twice daily for 8 weeks in previously untrained young men starting resistance training: significant testosterone increase (~15%, mean +~96 ng/dL vs +~18 in placebo), greater strength and muscle gains, and improved recovery vs placebo

  • Mahdi et al.2011

    675 mg root extract for 90 days in stressed/subfertile men: improved testosterone, LH, FSH, and sperm parameters

  • Lopresti et al.2019

    Anxiolytic RCT showing reduced cortisol and secondary improvement in testosterone, reinforcing the stress-axis mechanism