Ashwagandha
Withania somnifera — adaptogenic herb
Small short-term trials support modest reductions in perceived stress and anxiety, with some evidence of lower cortisol. Evidence for raising testosterone is weak. A real hepatotoxicity signal, and possible effects on thyroid hormone levels, mean this is not a risk-free supplement.
How confident is BioSignal?
Our overall position, and how sure we are of it across each dimension — including where we are not sure at all.
Limited evidence
Small short-term trials support modest reductions in perceived stress and anxiety, with some evidence of lower cortisol. Evidence for raising testosterone is weak. A real hepatotoxicity signal, and possible effects on thyroid hormone levels, mean this is not a risk-free supplement.
Early or sparse human evidence; conclusions remain uncertain.
Biological Role
Ashwagandha is not a nutrient and has no role in normal human physiology. Its withanolide compounds have plausible effects on the stress axis, but plausibility is where the certainty ends.
Human Evidence
Multiple small randomised trials, but they are short, heterogeneous in extract and dose, and a substantial share come from a narrow set of research groups with commercial ties.
Supplement Benefit
A modest, reasonably reproducible effect on perceived stress and anxiety scales. This is the one claim that holds up at all.
Broader Claims
Testosterone, muscle, fertility, and cognition claims rest on small trials, often in stressed or infertile men, and do not support the general marketing.
Safety Confidence
A genuine hepatotoxicity signal — cases of liver injury reported internationally, with regulatory warnings issued in some countries. It may also raise thyroid hormone levels.
Research Activity
Commercially very active; the independent, adequately powered research the category needs is largely absent.
Where the evidence stands today
How mature the science is, what kinds of evidence exist, and — the part nobody else prints — what is still missing.
3/9
steps proven in humans
Partly established
3 steps not demonstrated: Large human RCTs · Clinical outcomes · Guideline / regulatory support
Guideline / regulatory support
Not shownNot recommended; some regulators have issued safety warnings.
Clinical outcomes
Not shownNo clinical outcome data.
Large human RCTs
Not shownNone.
Small human outcome trials
LimitedSmall, short, subjective, industry-adjacent.
Human safety data
LimitedShort-term tolerability; hepatotoxicity signal unresolved.
Human biomarker / pharmacology
LimitedModest cortisol reductions of unclear clinical meaning.
Animal
ProvenAnxiolytic-type effects reported.
Cell / in vitro
ProvenReceptor and signalling studies.
Mechanistic plausibility
ProvenWithanolides plausibly modulate the stress axis.
The bottom line
What we know, what we think, what we don't know — and what would change our mind.
What We Know
Small randomised trials consistently report modest reductions in perceived stress and anxiety scores, and several report lower cortisol. Of the popular 'hormone' supplements, this is the one with real human data behind it.
What We Think
The stress effect is probably real but modest. The testosterone claims that drive much of the marketing are not well supported — the trials are small and often in men who were stressed or subfertile to begin with.
What We Don't Know
Whether the benefits persist beyond the few weeks trials have measured, and whether the liver-injury cases reflect the herb itself, particular extracts, or contamination. That question is genuinely open, and it is not a small one.
Active Research
Stress, sleep, and anxiety endpoints; a growing pharmacovigilance literature on hepatotoxicity.
What Could Change Our Mind
Larger, longer, independent trials with standardised extracts — and a clear resolution of the liver-safety question in either direction.
The biggest myth
“Ashwagandha is safe because it is natural and has been used for centuries”
Traditional use is not a safety study. Modern concentrated extracts differ substantially from traditional preparations, and the liver-injury reports are a modern, documented phenomenon.
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Why people take ashwagandha
Popularity is not evidence — but it is not stupid either. This explains the interest on its own terms.
Ashwagandha is the flagship of the 'natural hormone optimisation' market, promising lower stress and higher testosterone. The honest picture: a modest, probably real effect on stress; weak testosterone evidence; and a genuine liver-injury signal that almost nobody selling it will mention.
If you're here because…
Jump straight to the part of the evidence that answers your question.
Approval, safety and regulatory
What it is approved for, who should be careful, what remains unknown — and the limits of what this evidence can tell you.
Regulatory status
Not an approved drug (dietary supplement; not premarket-tested for efficacy or purity)
Availability
Over-the-counter supplement
Sport (WADA)
Not a prohibited class (confirm at publication)
Known safety profile
Ashwagandha is generally well tolerated in short trials, but it is not a risk-free supplement. The hepatotoxicity signal is real and is the most important thing on this page that the product label will not tell you.
Common issues
- Gastrointestinal upset
- Drowsiness
- Liver injury (uncommon but reported; regulatory warnings issued in some countries)
- Possible increase in thyroid hormone levels
Use caution if
- People with liver disease, or taking other hepatotoxic medications
- People with thyroid disease or taking levothyroxine (may raise thyroid hormone levels)
- People who are pregnant (traditionally avoided; potential abortifacient effects) or breastfeeding
- People taking sedatives, immunosuppressants, or thyroid medication
- People with hormone-sensitive conditions (limited data)
Long-term unknowns
Trials rarely run beyond a few months, so long-term safety — including liver safety with sustained use of concentrated extracts — is essentially uncharacterised.
Limits of this evidence
The evidence base is small, short, heterogeneous in extract, and substantially industry-linked — a combination that reliably inflates apparent effect sizes. Meanwhile the safety literature is growing in the opposite direction. That asymmetry is the honest summary of this supplement.
Full regulatory and sport detail
- Regulatory approval
- Not FDA-approved as a drug; sold as a dietary supplement (not premarket-tested for efficacy or purity).
- Approved indication
- None.
- Research chemical
- N/A — a widely sold herbal supplement; extract standardisation varies substantially between products.
- Sport (WADA)
- Not a WADA-prohibited class — confirm against the current list.
- Publication note
- Re-confirm regulatory status and current safety communications (including hepatotoxicity warnings) against primary sources at publication — this is a moving area.
Demand, separated from evidence
Every claim people make about this, counted against what the evidence actually showed.
BioSignal evaluated 8 popular claims about ashwagandha.
Here is where each one landed — including the claims of harm, where “not established” is reassuring rather than damning.
- Supported by evidence
- 1
- Mixed evidence
- 3
- Insufficient evidence
- 2
- Not established
- 2
Popularity is not evidence. This is simply a count of every claim BioSignal evaluated on this page, sorted by what the evidence actually showed — the full reasoning behind each verdict is in the Evidence Review below.
Supported by evidence
- Ashwagandha can cause liver injury
Mixed evidence
- Ashwagandha reduces stress and anxiety
- Ashwagandha lowers cortisol
- Ashwagandha improves sleep
Insufficient evidence
- Ashwagandha raises testosterone
- Ashwagandha builds muscle and strength
Not established
- Ashwagandha is safe because it is natural and has been used for centuries
- Ashwagandha is safe for people with thyroid disease
The evidence review
Every claim with the reasoning behind its verdict, the doses actually studied, where scientists agree and disagree, and the questions still open.
What people claim
Every popular claim, with BioSignal’s verdict and how confident we are in it. The verdicts are always visible; open any claim to read the evidence behind it.
Ashwagandha reduces stress and anxietyMixedLimited evidence
Multiple small randomised trials report modest improvements on perceived stress and anxiety scales. This is its best-supported claim, but the trials are small, short, and frequently industry-linked.
Ashwagandha lowers cortisolMixedLimited evidence
Several small trials report reductions in serum cortisol. Whether a modest cortisol change produces any meaningful clinical benefit is a separate question, and it has not been answered.
Ashwagandha raises testosteroneInsufficient evidenceLimited evidence
Some small trials report modest increases, typically in men who were stressed, subfertile, or resistance-training. There is no good evidence that it meaningfully raises testosterone in healthy men, and it is not a substitute for treating genuine hypogonadism.
Ashwagandha improves sleepMixedLimited evidence
Small trials report improvements in sleep quality, often alongside the reduction in stress. Results are inconsistent and the trials are small.
Ashwagandha can cause liver injurySupportedModerate confidence
Cases of ashwagandha-associated liver injury have been reported in several countries, and some regulators have issued warnings. It is uncommon, and causation in individual cases is hard to prove — but this is a real signal, not a theoretical concern, and it is rarely mentioned at the point of sale.
Ashwagandha builds muscle and strengthInsufficient evidenceLimited evidence
A few small trials report modest effects alongside resistance training. The evidence is far too thin to support the claim, and resistance training itself does the work.
Ashwagandha is safe for people with thyroid diseaseNot establishedLimited evidence
Ashwagandha may increase thyroid hormone levels. For someone taking levothyroxine, or with an overactive thyroid, this is a genuine and under-recognised interaction.
Doses used in human studies
What was actually given to participants in the research. These are descriptions of studies, not recommendations.
Adults with stress or anxiety
- Intervention
- Standardised root extract
- Dose
- ~250–600 mg/day (as used in trials)
- Duration
- 6–8 weeks in most trials
- Outcome
- Perceived stress and anxiety scales; serum cortisol
- Notes
- Descriptive of trial protocols, not a recommendation. Extracts differ substantially between products
Adults (sleep)
- Intervention
- Standardised root extract
- Dose
- ~300–600 mg/day
- Duration
- 6–8 weeks
- Outcome
- Subjective sleep quality
- Notes
- Small trials; inconsistent results
Men (testosterone / fertility studies)
- Intervention
- Root extract
- Dose
- ~300–675 mg/day in reported trials
- Duration
- 8–12 weeks
- Outcome
- Testosterone and semen parameters
- Notes
- Typically in stressed or subfertile men; does not support use in healthy men or as hypogonadism treatment
Long-term use
- Intervention
- Ashwagandha
- Dose
- Not established
- Duration
- Not established
- Outcome
- Not studied
- Notes
- Trials rarely exceed a few months; long-term safety — including liver safety — is uncharacterised
Where scientists agree — and don’t
Agreed
- Small trials support a modest reduction in perceived stress and anxiety.
- Trials are small, short, and heterogeneous in extract and dose.
- Cases of liver injury have been reported and some regulators have issued warnings.
- It is not a treatment for hypogonadism or thyroid disease.
Debated
- Whether the reported cortisol reductions have any clinical meaning.
- Whether it meaningfully affects testosterone in any population.
- How much of the published benefit reflects industry-linked study designs.
Unknown
- Whether the hepatotoxicity relates to the herb, specific extracts, or contamination.
- Whether benefits persist beyond a few weeks.
- Long-term safety with continued use.
What remains unknown
- Does the hepatotoxicity signal reflect the herb itself, particular extracts, or adulteration?
- Do the stress benefits persist beyond the 6–8 weeks that trials have measured?
- Is there any population in which ashwagandha meaningfully raises testosterone?
- How much of the positive literature would survive independent, non-industry replication?
Questions people actually ask
What is ashwagandha?
Ashwagandha (Withania somnifera) is a herb long used in Ayurvedic practice and now sold widely as an 'adaptogen' — a marketing category rather than a pharmacological one. It is not a nutrient, and your body has no requirement for it.
Does ashwagandha actually work for stress?
Probably, modestly. Several small randomised trials report reductions in perceived stress and anxiety scores, and some report lower cortisol. That makes it the best-evidenced supplement in this category — though the trials are small, short, and many come from research groups with commercial ties, so the effect is likely smaller than the marketing suggests.
Will ashwagandha raise my testosterone?
There is no good evidence that it will, especially if you are healthy. The trials that report increases are small and usually involve men who were stressed, subfertile, or beginning resistance training — and even then the changes are modest. It is not a treatment for low testosterone, and if you genuinely have hypogonadism, this is not the answer.
Is ashwagandha safe?
Mostly well tolerated — but there is a genuine caveat that the supplement aisle does not mention. Cases of ashwagandha-associated liver injury have been reported in several countries, and some regulators have issued warnings. It is uncommon, but it is a real signal. It may also raise thyroid hormone levels, which matters if you have thyroid disease. 'Natural' is not the same as 'harmless'.
What actually works better for stress?
Sleep, exercise, and — for persistent anxiety — cognitive behavioural therapy all have substantially stronger evidence than any supplement. If stress is genuinely affecting your life, those are the interventions worth your effort. Ashwagandha is a low-cost experiment, not a strategy.
Practical takeaways
- Ashwagandha has the best evidence of the popular hormone supplements — a modest effect on stress and anxiety.
- The trials are small, short, industry-adjacent, and use different extracts. Treat the effect size with caution.
- The testosterone claims that sell it are not well supported, particularly in healthy men.
- There is a genuine liver-injury signal, with regulatory warnings in some countries. This is rarely mentioned at the point of sale.
- It may raise thyroid hormone levels — a real concern if you have thyroid disease or take levothyroxine.
How it works
The mechanism comes last on purpose. A compelling explanation of how something might work is the easiest part of the story to tell, and the part most likely to outlive the evidence for it.
Ashwagandha is not a nutrient and has no role in normal human physiology. Its withanolide compounds have plausible effects on the stress axis, but plausibility is where the certainty ends.
How we found out
Traditional Use
Withania somnifera has a long history in Ayurvedic practice, in preparations quite different from today's concentrated standardised extracts.
The Adaptogen Era
Ashwagandha became the flagship of the 'adaptogen' supplement category, marketed for stress, cortisol, testosterone, sleep, and performance.
The Small-Trial Literature
A body of small randomised trials accumulated, reporting modest reductions in perceived stress and cortisol — and much weaker, less consistent effects on testosterone.
The Liver Safety Signal
Cases of ashwagandha-associated liver injury were reported internationally, prompting regulatory warnings in some countries and a reassessment of a supplement previously assumed to be benign.
References
Verified sources. BioSignal does not print a citation it has not checked.
References for this record are being verified and will be published with the next review. BioSignal does not print citations it has not checked.
Version history
Version 1.0
Initial record for the Hormonal Health Ecosystem, authored to the Creatine benchmark. Calibration: Emerging maturity, limited confidence, safety caution flagged. The hepatotoxicity signal is elevated into the claims and safety surfaces because it is real, under-disclosed, and material to the decision. Review cadence: Annually.
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