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Adaptogen

Ashwagandha · Withania somnifera (KSM-66)

The best-studied adaptogen for stress and sleep.

B
Evidence grade
Human RCTs, biomarker outcomes
Strongest study
Tier 1 · 2 linked studies

Short answer

One of the few 'traditional' herbs with solid modern trial data. Choose KSM-66 or Sensoril, branded extracts with standardised withanolides.

Product and dose overview

Ashwagandha (Withania somnifera (KSM-66)) is a adaptogen with evidence grade B, meaning it is supported by human RCTs. We track 9 products containing Ashwagandha. Typical doses range from 120 to 600 mg per serving. The top-ranked product scores 7.7 out of 10 on our composite scale (dose, evidence, price, testing, transparency). Prices range up to $32.99 per month.

Evidence grade: B Products in database: 9 Category: Adaptogen

Top Ashwagandha products

ProductBrandDosePrice/mo3rd-party testedScore
KSM-66 Ashwagandha SupplementDouble Wood Supplements600 mg$19.95Yes7.7
KSM-66 Capsules | Ashwagandha RootNootropics Depot300 mg$19.99Yes7.7
Full Spectrum Ashwagandha - 60 capsulesProHealth Longevity600 mg$32.99Yes7.6
Ashwagandha Extract PowderBulkSupplements600 mg$20.97No7.0
Jarrow Formulas Ashwagandha (KSM-66), 300 mgJarrow Formulas300 mg$28.92No6.8

Scores are editorial judgments, not a scientific standard. See how we score.

What it is

A root used in Ayurvedic medicine for thousands of years. Modern trials show it blunts stress hormones (cortisol) and improves sleep quality.

Why people take it

600 mg/day of a standardised extract reduces perceived stress and lowers cortisol ~20% in a couple of months. Also shows benefits in sleep, testosterone (in men), and gym performance.

Our verdict

One of the few 'traditional' herbs with solid modern trial data. Choose KSM-66 or Sensoril, branded extracts with standardised withanolides.

Structure & class

Withania somnifera root extract. Contains withanolides (KSM-66 standardised to 5%).

Mechanism & clinical data

Chandrasekhar 2012 showed 300 mg BID reduced Perceived Stress Scale scores 44% over 60 days. Meta-analyses confirm anxiolytic effect and cortisol lowering.

Pharmacokinetics

Multi-day biological effect.

Dose & forms

Trial dose
600 mg
/ day
Range in trials
300 to 1200 mg
/ day
Common forms
KSM-66 capsule, Sensoril capsule, Powder

What to watch out for

Not for pregnancy, hyperthyroidism, or with sedatives. Effects on TSH can complicate thyroid conditions.

Safety limits and interactions

When a product exceeds the UL or contains an ingredient with clinically significant interactions, a "Review advised" flag appears on its product page and links here.

Known drug interactions
May potentiate thyroid hormone replacement (levothyroxine), raising risk of hyperthyroid symptoms; caution advised with sedatives, immunosuppressants, and blood sugar/blood pressure medications due to additive effects. Avoid in patients with cirrhosis or advanced chronic liver disease.
Safety note
No formal UL established. Generally well tolerated at standard doses (300-1,000 mg/day, with 2,000 mg/day shown safe over 12 weeks in trials), but rare cases of clinically apparent drug-induced liver injury have been reported (typically at doses above 1,000 mg/day for extended periods), and it can stimulate thyroid hormone production, posing risk for those with hyperthyroidism or on thyroid medication.

Source: https://www.ncbi.nlm.nih.gov/books/NBK548536/

Where this dose comes from

The trial dose above is our editorial pick from the published human trials for this ingredient. We choose the dose that the best-available studies used on the endpoint most relevant to longevity. The range shows the lowest and highest doses tested in published trials. The landmark studies below are the papers we read to set it. You can click through and check our work.

When new trials publish, our automated sweeps flag them. If a new study materially changes the dose, we update it through editorial review and record the old dose, new dose, and the triggering study in every affected product's recommendation history. The dose is never changed automatically.

Regulatory status

EUFood supplement (novel status in some countries)
USDietary supplement
UKFood supplement
CANHP

Timeline

Regulatory events, evidence grade changes, and key research milestones for Ashwagandha, most recent first. Studies link to the paper; regulatory entries name and link the responsible authority.

  • 2025-04 Regulatory single source
    EU Court sharpens the bar for botanical health claims
    A Court of Justice of the European Union ruling in April 2025 further tightened the requirements for how botanical ingredients (herbs, plant extracts) can be marketed with health claims in the EU, effectively removing much of the flexibility of the on-hold list.
  • 2024-06 Regulatory confirmed
    EU heads of food safety agencies prioritize ashwagandha for restriction
    The HoA Working Group on Food Supplements (26 European countries, chaired by BVL Germany and NVWA Netherlands) published its first report identifying 117 supplement substances as potential health risks. Ashwagandha (Withania somnifera) was among 12 substances prioritized for Article 8 restriction under Regulation (EC) No 1925/2006. The BfR separately recommended ashwagandha root be placed in Annex III Part C (substances under Community scrutiny) based on liver toxicity case reports. Germany and the Netherlands formally submitted the 12 priority substances to the European Commission in September 2024 to initiate the procedure.
    Source →
  • 2024-06 Regulatory confirmed
    EU report identifies 117 supplement substances as potential health risks
    The HoA Working Group on Food Supplements (26 European countries) published its first report evaluating 117 substances used in food supplements. Of these, 65 were assessed as likely novel foods, 6 were already regulated, 34 had insufficient data, and 12 were prioritized for Article 8 restriction under Regulation (EC) No 1925/2006. The 12 priority substances include ashwagandha, curcumin, melatonin, piperine, St. John's wort, coumarin, p-synephrine, maca, holy basil, Melaleuca, black cohosh, and L-tryptophan. The report drew on 1,500 RASFF alerts reviewed between 2017 and mid-2022.
    Source →
  • 2021 Research milestone
    Gopukumar et al. 2021 (cognition in stressed adults)
    90-day RCT, 130 chronically stressed adults, 300 mg sustained-release ashwagandha: significant improvements in memory and focus scores plus reduced cortisol.
    Source →
  • 2012 Research milestone
    Chandrasekhar et al. 2012
    600 mg KSM-66/day for 60 days significantly reduced stress and cortisol.
    Source →
  • 2006-12 Regulatory confirmed
    EU Health Claims Regulation adopted
    Regulation (EC) No 1924/2006 laid down harmonised rules for nutrition and health claims made on foods, including supplements. Only claims listed in the EU Register of authorised claims can be used. Rejected botanical claims are held in a separate on-hold list.
    Source →
  • 1997 Regulatory confirmed
    EU introduces the Novel Food Regulation
    Regulation (EC) No 258/97 required any food or food ingredient without a history of consumption in the EU before 15 May 1997 to be authorised before being placed on the market. This is the framework that captures NMN, spermidine as a supplement ingredient, urolithin A, and many other longevity actives.
    Source →
2026 evidence refresh

Ashwagandha (KSM-66 extract) lowers serum cortisol and stress scores in chronically stressed adults, with rare but real liver injury case reports.

Verified 2026-06-16. We update this section as new peer-reviewed trials land.

Human RCT base
40+ (with KSM-66 extract specifically)
peer-reviewed randomised trials
Largest single trial
n = 873
A 2025 meta-analysis of 15 RCTs found ashwagandha supplementation significantly reduced cortisol levels and improved Hamilton Anxiety Rating Scale scores across studies. source

Best-supported claim

Ashwagandha's best-supported claim is cortisol and stress reduction, using the specific KSM-66 root extract standardized to 5% withanolides. The foundational trial by Chandrasekhar, Kapoor, and Anishetty randomized 64 chronically stressed adults to 300 mg KSM-66 twice daily or placebo for 60 days, finding a 27.9% reduction in serum cortisol versus 7.9% in placebo (p=0.002), alongside a 44% reduction in Perceived Stress Scale scores (https://ksm66ashwagandhaa.com/wp-content/uploads/2018/02/65999KSM66AshwagandhaInfoNo1.pdf). Two independent 2025 meta-analyses reinforced this: one pooling 15 RCTs and 873 adults found significant cortisol reduction and anxiety scale improvement, and another pooling 7 RCTs and 488 participants found a pooled cortisol reduction of -1.16 micrograms/dL (95% CI -1.64 to -0.69, p<0.001). For male fertility, a pilot study of oligospermic men found 90 days of ashwagandha root extract increased sperm concentration by 167% and testosterone by 17% versus baseline, though this was not placebo-controlled for the sperm outcome and needs replication with a control arm (https://pmc.ncbi.nlm.nih.gov/articles/PMC3863556/).

Not supported by the evidence base

Ashwagandha is marketed as a broad hormone optimizer for testosterone in all men, but the evidence is more selective than that framing suggests. A randomized, double-blind, placebo-controlled crossover trial in healthy males aged 40-70 found ashwagandha increased DHEA-S and testosterone significantly versus placebo, but found no significant effect on cortisol, estradiol, fatigue, vigor, or sexual well-being, meaning the hormone changes did not translate into subjectively noticeable benefits in this healthy population (https://pmc.ncbi.nlm.nih.gov/articles/PMC6438434/). Marketers also frequently omit ashwagandha's documented, if rare, liver risk: a case series identified 6 to 10 documented cases of ashwagandha-induced liver injury with jaundice, at doses as low as 450 mg/day, occurring 2 to 12 weeks into supplementation, though all reported cases were reversible after stopping. Most controlled trials at 300-600 mg/day for 8-12 weeks found no significant change in liver enzymes, so the injury risk appears real but rare rather than a typical dose-response effect.

Typical dose

300 mg twice daily (600 mg/day total) of KSM-66 root extract standardized to at least 5% withanolides

Safety

In the KSM-66-specific evidence base, safety studies including a 12-month trial in 191 participants found no clinically relevant changes in liver enzymes (AST, ALT) or thyroid hormones at 600 mg/day (https://pmc.ncbi.nlm.nih.gov/articles/PMC12986965/). Side-effect rates in KSM-66 trials were comparable between active treatment and placebo groups (around 4% in both). However, documented case reports exist of ashwagandha-induced liver injury, including a case series covering 6-10 cases with a cholestatic or mixed hepatocellular pattern, typically resolving within 1-9 months of stopping. Ashwagandha can raise thyroid hormones (T3, T4) and lower TSH in people with subclinical hypothyroidism, making it contraindicated in hyperthyroidism or Graves' disease. It is contraindicated in pregnancy.

Interactions worth flagging

  • thyroid medications (levothyroxine)
  • sedatives, benzodiazepines, and sleep medications (additive sedation via GABA activity)
  • immunosuppressants
  • diabetes medications (may lower blood sugar further)

Three recent studies to know

  • Ashwagandha supplementation and cortisol, anxiety outcomes: a systematic review and meta-analysis
    BJPsych Open 2025

    Read study →
  • The Clinical Implications of Ashwagandha (Withania somnifera) on Liver and Thyroid Function
    PMC (peer-reviewed review) 2026

    Read study →
  • A Randomized, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha in Aging, Overweight Males
    American Journal of Men's Health 2019

    Read study →

Landmark studies

Found in these products (9)

All products in our catalog that contain Ashwagandha, ranked by our overall score. Ranking is editorial, never paid.

Double Wood Supplements
KSM-66 Ashwagandha Supplement
Adaptogen
Extract per serving
Ashwagandha 600 mgCapsule · 60 servings
Price per serving
$0.33$19.95 · 60 servings
Testing
3rd-party listed · public lab certificate

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 7.7/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

100%
of trial dose
$0.33
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with doublewoodsupplements.com
Adaptogen
Extract per serving
Ashwagandha 300 mgCapsule · 90 servings
Price per serving
$0.22$19.99 · 90 servings
Testing
3rd-party listed · public lab certificate

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 7.7/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

100%
of trial dose
$0.44
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with nootropicsdepot.com
Adaptogen
Extract per serving
Ashwagandha 600 mgCapsule · 30 servings
Price per serving
$1.10$32.99 · 30 servings
Testing
3rd-party listed · public lab certificate

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 7.6/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

100%
of trial dose
$1.10
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with www.prohealth.com
BulkSupplements
Ashwagandha Extract Powder
Adaptogen
Extract per serving
Ashwagandha 600 mgPowder · 166 servings
Price per serving
$0.13$20.97 · 166 servings
Testing
None listed

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 7.0/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

100%
of trial dose
$0.13
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with www.bulksupplements.com
Adaptogen
Extract per serving
Ashwagandha 300 mgCapsule · 120 servings
Price per serving
$0.24$28.92 · 120 servings
Testing
None listed

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 6.8/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

100%
of trial dose
$0.48
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with jarrow.com
AG1 (Athletic Greens)
AGZ: Nightly Sleep Support
Adaptogen
Ingredients listed
8 ingredients listedlargest listed: Glycine 2,000 mg
Price per serving
$3.30$99.00 · 30 servings
Testing
3rd-party listed · no public lab certificate

Elemental vs compound: check label

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 6.7/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

100%
of trial dose
$3.96
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with drinkag1.com
Adaptogen
Extract per serving
Ashwagandha 120 mgCapsule · 30 servings
Price per serving
$0.67$19.99 · 30 servings
Testing
3rd-party listed · public lab certificate

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 5.9/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

40%
of trial dose
$3.33
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with nootropicsdepot.com
Cognition
Active per serving
Ashwagandha 125 mgTablet · 30 servings
Price per serving
$1.33$39.94 · 30 servings
Testing
3rd-party listed · no public lab certificate

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 5.5/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

42%
of trial dose
$6.39
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with www.lifeextension.com
Thorne HealthTech
Ashwagandha
Adaptogen
Extract per serving
Ashwagandha 120 mgCapsule · 30 servings
Price per serving
$0.73$22.00 · 30 servings
Testing
3rd-party listed · no public lab certificate

Status as recorded in the catalog from brand materials; not independently verified by NO1GEVITY.

Score & research context 5.3/10

Editorial score, not proof that this product works. Research-dose calculations are not dosing advice.

40%
of trial dose
$3.67
per research-dose day, not label serving
0Trial dose2×
Catalog price · Confirm current price with www.thorne.com
Editorial guides

Buying guides and comparisons

Neighbouring molecules

Related ingredients

See all in Adaptogen →

Molecules in the same class, plus the actives most often formulated alongside Ashwagandha in our catalogue.

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Product shelves
See all in Adaptogen (8)See all in Cognition (1)

See Ashwagandha in context: the mechanism it acts through, the biomarker it moves, the products that dose it, and the trials that tested it.

View Ashwagandha on the Longevity Map →

Frequently asked questions

What is Ashwagandha?

A root used in Ayurvedic medicine for thousands of years. Modern trials show it blunts stress hormones (cortisol) and improves sleep quality.

What dose of Ashwagandha should I take?

The trial dose in published human studies is 600 mg per day, with a range of 300 to 1200 mg per day. Always consult a qualified clinician before starting any supplement.

Is Ashwagandha safe?

No formal UL established. Generally well tolerated at standard doses (300-1,000 mg/day, with 2,000 mg/day shown safe over 12 weeks in trials), but rare cases of clinically apparent drug-induced liver injury have been reported (typically at doses above 1,000 mg/day for extended periods), and it can stimulate thyroid hormone production, posing risk for those with hyperthyroidism or on thyroid medication.

What is the best Ashwagandha supplement?

We track 9 products containing Ashwagandha. The top-ranked product scores 7.7 out of 10 on our composite scale, which evaluates dose, evidence, price, third-party testing, and transparency. See the comparison table above. Scores are editorial judgments, not a scientific standard.

What is the evidence grade for Ashwagandha?

Ashwagandha has evidence grade B, meaning it is supported by human RCTs. Grade A means replicated human RCTs with hard endpoints. Grade B means human RCTs with biomarker outcomes. Grade C means mixed or small human trials. See our evidence grading methodology.

Independently checked

Data verification

Evidence grade
B
Human RCTs, biomarker outcomes
Research dose
600 mg
Products tracked
9
Updated continuously
Safety signal
No formal UL established. Generally well tolerated at sta...

Evidence grades are reviewed when new human RCTs are published. Product counts update automatically as new products are added. Dose ranges reflect published trial data, not brand recommendations. Read how we verify.