Ashwagandha
Withania somnifera · Ayurvedic Rasayana
Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.
The evidence for stress and cortisol reduction is consistent across several meta-analyses but rests on small, short, mostly industry-linked trials, so it lands at mixed-to-moderate RCT support rather than strong multi-RCT consensus. Bachour and colleagues (2025, BJPsych Open) pooled fifteen RCTs and 873 adults and found significant reductions in morning cortisol (mean difference -2.36, 95% CI -3.26 to -1.46), perceived stress (PSS -4.88), and anxiety (HAM-A -3.52 at eight weeks). An earlier meta-analysis of nine RCTs and 558 participants reported similar reductions in perceived stress, anxiety, and serum cortisol. For sleep, Cheah and colleagues (2021, PLOS One) pooled five RCTs and 400 people and found a small but significant benefit (SMD -0.59), strongest at 600 mg daily for at least eight weeks in people diagnosed with insomnia. The honest caveats are large: most trials ran three months or less, used proprietary standardized extracts (KSM-66, Sensoril, Shoden) tied to their manufacturers, enrolled small samples, and the NIH NCCIH still calls the anxiety evidence 'unclear' and the overall base limited by small sizes and heterogeneous preparations. Cortisol reduction is the most replicated single finding; the downstream clinical claims are softer.
- FDA
- Legal supplement (DSHEA)
- WADA
- Not prohibited
Reference only. Not medical advice.
What can go wrong
Rising signal of idiosyncratic liver injury (LiverTox score B); avoid in liver disease, pregnancy, and uncontrolled thyroid or autoimmune conditions, and confirm with a clinician.
Ashwagandha is the root of Withania somnifera, a shrub used in Ayurvedic medicine for more than two thousand years as a rasayana, or rejuvenating tonic. It is the most-studied adaptogen of the modern supplement era, and the strongest, most replicated finding is a reduction in morning cortisol, with associated improvements in perceived stress, anxiety, and sleep. The catch is that most of those trials are small, run three months or less, and use proprietary extracts funded by the companies that sell them, so the honest grade is moderate rather than strong. A separate concern has been rising since 2017: documented cases of idiosyncratic liver injury, which earned ashwagandha a 'likely cause' rating from the NIH LiverTox database and prompted Denmark to ban it from food supplements in 2023.
Most-researched adaptogen of the modern era, with the cortisol data to back it up.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
How it is supposed to work
Withanolides and withaferins, the active steroidal lactones in ashwagandha root, modulate the hypothalamic-pituitary-adrenal axis, the body's central stress system. Cortisol production drops about twenty-five to thirty percent over four to eight weeks of supplementation in stressed adults. The mechanism extends to GABA-receptor activity (which is part of the sleep effect) and modest testosterone-supporting actions in men. The pathways are well-characterized; the proprietary extracts (KSM-66, Sensoril) standardize different fractions of the same root.
How it is taken
The two best-evidenced protocols are 300-600mg/day of KSM-66 (most modern stress and sleep trials) or 125-250mg/day of Sensoril (older Auddy 2008 stress trial inheritance). Effects on cortisol and stress accumulate over 4-8 weeks; sleep effects may be observable within 2 weeks. Take with food to minimize occasional GI discomfort. Timing matters less than consistency, daily use for at least 8 weeks before evaluating effect. Evening dosing may help sleep onset; morning dosing may suit cortisol-reduction protocols where the goal is dampening the morning cortisol awakening response. A baseline liver panel (ALT, AST, alkaline phosphatase) before long-term use is sensible given the rare hepatotoxicity reports that led to Iceland and Denmark sales restrictions.
- KSM-66
- 300-600mg/day, with food
- Sensoril
- 125-250mg/day, with food
- Sleep emphasis
- Evening dose, 1-2 hours before bed
- Cortisol emphasis
- Morning or split AM/PM
- Time to effect
- Sleep: 1-2 weeks. Cortisol/stress: 4-8 weeks.
- Trial duration
- Most evidence is 8-12 weeks; long-term safety less established
- Baseline labs
- Liver panel before chronic use given hepatotoxicity signal
- Cycling
- Common practice but weak evidence; no tolerance documented
Which form to buy
Not all preparations of the same ingredient are the same thing, and the trials were run on particular ones.
KSM-66® Ashwagandha (Ixoreal Biomed)
The most-clinically-studied branded ashwagandha extract. Root-only (no leaf), standardized to 5% withanolides. Used in Lopresti 2019, Salve 2019, and most of the cortisol-reduction clinical literature. Full-spectrum extraction process retains the broad withanolide profile rather than concentrating a single fraction.
Sensoril® Ashwagandha (Natreon)
Root and leaf, standardized to 10% withanolides. The Auddy 2008 foundational stress trial used this extract. More concentrated withanolide content per gram than KSM-66; effective doses are correspondingly lower. Different clinical inheritance from KSM-66; head-to-head comparison literature is thin.
Shoden® (Arjuna Natural)
Newer branded extract standardized to 35% withanolide glycosides. Building a clinical evidence base for sleep and stress. Lower doses required (60-120mg) due to higher concentration. Some emerging trials; less established than KSM-66 or Sensoril.
Generic "Ashwagandha Extract"
Many consumer products use unstandardized or low-standardization (1-2.5% withanolides) generic extracts. These may be substantially subclinical at labeled doses. The brand name on the label matters; "ashwagandha root extract" without standardization disclosure is essentially unverified.
Whole Root Powder
Traditional Ayurvedic preparation, dried root powder rather than concentrated extract. Effective doses are substantially higher (3-6g/day) to match extract withanolide content. Reasonable choice for users preferring traditional preparation; verify ayurvedic supplier quality.
Ashwagandha Tincture
Alcohol or glycerin-based liquid extract. Variable standardization. Acceptable for users preferring liquid forms; dose precision is less consistent than standardized capsules.
Combination "Calm" Blends
Many consumer products combine ashwagandha with other adaptogens (rhodiola, holy basil), L-theanine, magnesium, or melatonin at sub-clinical individual doses. Marketing-driven; rarely deliver the studied withanolide content in clinical trials. Verify the individual ashwagandha dose.
Who it works for, and who it does not
Chronic stress with elevated cortisol
The clearest indication. Lopresti 2019 and a dozen replication trials demonstrate ~25-30% reduction in morning cortisol over 4-8 weeks at 300-600mg KSM-66. Effect sizes large for a botanical supplement. The signature use case in the modern adaptogen literature.
Sleep onset and quality difficulty
Salve 2019 and subsequent trials show meaningful sleep improvements at 300mg twice daily for 8 weeks. Mechanism likely involves both cortisol reduction (HPA-axis) and GABA-pathway activity. Especially useful in stress-driven sleep difficulty.
Generalized anxiety symptoms (subclinical)
Multiple small RCTs in non-clinical anxiety populations show improvements in subjective anxiety scales over 8-12 weeks. Not appropriate as monotherapy for diagnosed anxiety disorders; useful adjunct for everyday stress symptoms.
Strength training and athletic recovery
Wankhede 2015 and subsequent studies suggest modest improvements in strength, muscle size, and recovery markers in trained men at 600mg/day for 8 weeks. Effect sizes smaller than creatine or training itself; reasonable adjunct.
Male fertility and testosterone
Preliminary trials suggest modest testosterone elevation (~15%) and improvements in sperm parameters in subfertile men. Effect more reliable in baseline-low cohorts. Not a substitute for medical evaluation of fertility issues.
Subclinical hypothyroidism
Sharma 2018 trial showed modest TSH normalization and T4 elevation at 600mg/day. Real interaction with thyroid axis, beneficial in some cases, problematic in others. Hashimoto's thyroiditis patients should coordinate with endocrinology before use.
Pregnancy and lactation
Traditional Ayurvedic use included as abortifacient at high doses; modern position is generally to avoid during pregnancy. Insufficient lactation safety data. Coordinate with OB-GYN rather than self-supplementing.
Chronic long-term use (6+ months)
Most trials are 8-12 weeks. The idiosyncratic hepatotoxicity signal (Iceland and Denmark restrictions) is rare but real; baseline and periodic liver panels are sensible for chronic use. Cycling protocols (4-6 weeks on, 2 weeks off) are common in practice but have weak evidence basis.
Taken with other things
Combinations people actually use. Evidence for one ingredient is not evidence for a pair.
Magnesium Glycinate
Complementary stress mechanisms (ashwagandha: HPA-axis cortisol over weeks; magnesium: acute calming, GABA support, muscle relaxation). Common functional medicine combination for chronic stress with acute episodes. Evening combination for sleep is well-tolerated.
L-Theanine
Different timing mechanisms, L-theanine provides acute relaxation within hours; ashwagandha modulates baseline stress response over weeks. Reasonable combination for users facing both chronic and acute stress demands.
Rhodiola Rosea
The "two adaptogen" classical pairing, ashwagandha for calming (downregulating excess cortisol) and rhodiola for activating (combating fatigue). Different traditional inheritances; complementary modern uses.
Creatine
In strength training contexts, ashwagandha's modest recovery/strength signal pairs reasonably with creatine's well-established performance effects. Different mechanisms; complementary effects.
Thyroid medication (levothyroxine)
Ashwagandha modulates thyroid axis, has raised T4 and lowered TSH in clinical trials. Patients on thyroid replacement may need dose adjustment. Coordinate with endocrinology rather than self-supplementing.
Immunosuppressants
Ashwagandha has immunomodulating activity that may interact with prescribed immunosuppression (transplant, autoimmune disease management). Coordinate with prescribing physician.
Sedative medications (benzodiazepines, sleep medications)
Additive sedation possible at higher doses, particularly evening dosing. Generally well-tolerated but worth monitoring when combining.
Pregnancy and conception
Traditional contraindication during pregnancy. Insufficient modern safety data for routine use during conception attempts or pregnancy. Avoid without clinician guidance.
Alcohol
Theoretical additive hepatic burden given the rare hepatotoxicity signal. Heavy alcohol use combined with chronic ashwagandha warrants liver panel monitoring.
What to look for on the label
The most important quality marker is branded extract disclosure: KSM-66 (Ixoreal Biomed) or Sensoril (Natreon) on the label, with the standardization percentage (5% withanolides for KSM-66, 10% for Sensoril). Generic "ashwagandha root extract" without standardization is essentially unverified, withanolide content can vary by 10x across unspecified products. Premium brands disclose third-party testing for heavy metals (Ayurvedic herbs from India have historical concerns about lead and arsenic, mostly resolved in reputable supply chains). Avoid: unstandardized generic extract products; "calm blend" formulations that obscure individual ashwagandha withanolide dose; products from manufacturers without clear sourcing documentation; cheap mass-market products with no third-party testing.
Safety in detail
- Idiosyncratic liver injury has been documented in a small subset of users, leading to restricted sales in Iceland and Denmark. The mechanism is unclear and appears unrelated to dose. A baseline liver panel before long-term use is sensible.
- A subset of users (roughly 10-20%) report emotional blunting or dissociation rather than the typical calming effect. Stopping resolves the effect.
- Mild GI upset and drowsiness are the most common side effects.
- Not for pregnancy or breastfeeding without clinician guidance, traditional Ayurveda actually used it as an abortifacient at very high doses.
- Theoretical interaction with thyroid medication (raises T4); discuss with your endocrinologist if applicable.
What people get wrong
Often saidAshwagandha is universally safe because it's natural.
ActuallyMost users tolerate it well, but documented liver-injury cases in a small subset led Iceland and Denmark to restrict sales. The idiosyncratic risk is real even if rare.
Often saidKSM-66 and Sensoril are basically the same thing.
ActuallyThey're standardized to different active fractions and most clinical trials use one or the other. The KSM-66 versus Sensoril head-to-head literature is thin.
Often saidCycling on and off is necessary.
ActuallyNo clinical trial has demonstrated tolerance or required cycling. Some practitioners recommend cycling out of caution; the evidence for the practice is weak.
Who profits, and who pushes back
Einar Björnsson
The idiosyncratic hepatotoxicity is rare but real. We have documented cases that meet causality criteria. Routine population-level supplementation in the absence of monitoring is hard to defend on this evidence base alone.
Andrew Huberman
Recommends ashwagandha for stress in cycling protocols (4-6 weeks on, 2 weeks off) rather than continuous use. No financial relationship with supplement brands.
Mark Hyman
Long-standing functional medicine recommendation for stress, sleep, and adrenal support.
Ixoreal Biomed
Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.
Funds the majority of KSM-66 clinical trials and the marketing push that made ashwagandha mainstream.
Where the research comes from
Most of the published research on this comes from one place. 54% of it is from India. Findings that no unrelated group has reproduced are weaker than the study count makes them look.
| Place | Share of published research |
|---|---|
| India | 54% |
| United States | 22% |
| Europe | 14% |
| Australia | 10% |
Research published from: India.
How we got here
Ashwagandha (अश्वगन्धा, "horse-smell") appears in the Charaka Samhita and Sushruta Samhita, the foundational texts of Ayurveda, dating to roughly 200 BCE to 200 CE. Sanskrit Rasayana means rejuvenation tonic, the highest classification in Ayurvedic herbal medicine. The traditional indications are balya (strength), rasayana (rejuvenation), nidrajanaka (sleep promotion), and vajikarana (vitality / reproductive). Modern clinical research, beginning seriously in the 2000s, has substantially validated several of those traditional indications, particularly stress reduction and sleep quality.
- ~200 BCECharaka Samhita references ashwagandha as a Rasayana herb
- 2008Auddy Sensoril trial, foundational modern stress evidence
- 2012KSM-66 Ixoreal Biomed commercialization begins
- 2019Lopresti chronic-stress trial popularizes ashwagandha in Western wellness
- 2023Iceland restricts sales pending hepatotoxicity review
- 2024Denmark follows Iceland; Australia TGA review pending
What we do not know
- Why a small subset of users develops idiosyncratic liver injury when most don't.
- Whether KSM-66 (root-only, 5% withanolides) and Sensoril (root + leaf, 10% withanolides) produce meaningfully different clinical effects.
- Optimal duration of continuous use, most trials are 8-12 weeks; long-term data is thin.
- Whether the testosterone-supporting effects translate to fertility outcomes.
Legal status
Legal as a dietary supplement in the US under DSHEA. Restricted from sale in Iceland (2023) and Denmark (2024) pending review of hepatotoxicity case reports. Mainstream Western medical use is increasing, particularly for stress and sleep.
Status current as of July 2026. Regulatory positions change, sometimes quickly.
The market for this
What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.
Two proprietary extracts dominate the clinical-evidence base: KSM-66 (Ixoreal Biomed, root-only) and Sensoril (Natreon, root + leaf). Generic "ashwagandha extract" products often lack the standardization. Look for the named extract on the label.
At a glance
- Active compounds
- Withanolides (withaferin A and others)
- Standard dose
- 300-600mg/day of KSM-66 or 125-250mg/day Sensoril
- Cortisol effect
- ~25-30% reduction in morning cortisol
- Onset
- Effects typically observable within 2-4 weeks
- Trial duration
- Most RCTs are 8-12 weeks
- Sanskrit meaning
- "Horse-smell", refers to root odor and strength connotation
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.
Sources
LiverTox assigns ashwagandha likelihood score B (likely cause of clinically apparent liver injury); cases since 2017, cholestatic/mixed pattern, rare fatal/transplant cases in preexisting liver disease; withanolides most suspected.
Pivotal case series: 5 patients (3 Iceland 2017-2018, 2 US DILIN 2016), latency 2-12 weeks, cholestatic/mixed injury, prolonged pruritus and hyperbilirubinemia, no transplant, normalized in 1-5 months.
Meta-analysis of 15 RCTs and 873 adults: significant reductions in cortisol (-2.36, 95% CI -3.26 to -1.46), perceived stress (PSS -4.88), and anxiety (HAM-A -3.52 at 8 weeks); no significant quality-of-life change.
Meta-analysis of 5 RCTs and 400 participants: small but significant sleep benefit (SMD -0.59), strongest at >=600 mg/day, >=8 weeks, and in adults with insomnia; no serious adverse events.
NCCIH: evidence mixed, some benefit for insomnia and stress, effects on anxiety 'unclear'; many trials small with varied preparations; short-term use up to 3 months; liver-injury cases documented; avoid in pregnancy, breastfeeding, autoimmune and thyroid disorders, and before surgery.
NIH National Center for Complementary and Integrative Health
RUCAM causality analysis counts 12 well-documented cases (2017-2023), scores 6-8 ('probable'), most reports from Europe (Iceland, USA, Germany, UK); calls ashwagandha an emerging cause of herb-induced liver injury.
Denmark banned ashwagandha in food supplements (April 2023) after a 2020 DTU risk assessment; France ANSES issued a 2024 precautionary advisory; Poland set dose caps; Sweden/Finland/UK under review; most EU and US still permit it.
Independent critique of the supplement industry using ashwagandha: trials are small and mostly under 3 months, athletic studies use untrained subjects, proprietary extracts (KSM-66/Ixoreal, Sensoril, Shoden) dominate, and product mislabeling is common; stress effect real but 'far from definitive.'
Ayurvedic history: Sanskrit ashwa (horse) + gandha (smell); classified as rasayana; documented in Charaka Samhita; traditional uses for wasting, insomnia, nervous exhaustion, rheumatism, goiter; native to India and surrounding regions.
Danish ban analysis: DVFA banned ashwagandha as a food supplement after the 2020 DTU report citing effects on sex hormones, reproduction, metabolism, immune and central nervous system; authors dispute the strength of that evidence.
'Danish ban on Ashwagandha: Truth, evidence, ethics, and regulations,' PMC
Ashwagandha is not on the WADA 2025 Prohibited List and is permitted in sport, subject to strict-liability contamination risk; third-party certification advised.
The studies that matter
Lopresti 20192019
High-influence chronic-stress trial: KSM-66 240mg/day for 60 days produced about a 28% reduction in morning cortisol versus placebo.
Auddy 20082008
Foundational Sensoril trial: 125-500mg/day reduced cortisol and anxiety scores significantly.
Salve 20192019
Sleep-quality trial: 300mg twice daily for 8 weeks significantly improved sleep onset, total sleep time, and subjective quality.
Wankhede 20152015
Strength-training adjunct trial: significant improvements in muscle size, strength, and recovery in resistance-trained men.