How long does ashwagandha take to work?

Most RCTs measure outcomes at 8–12 weeks. Stress-scale improvements are often reported by week 4, but meaningful cortisol reductions typically require 6–8 weeks of consistent use.

Can ashwagandha raise testosterone?

One small RCT showed a modest increase in testosterone in men alongside a resistance training program. The evidence is preliminary and effect size is small. It should not be marketed primarily as a testosterone booster.

Is it safe to take ashwagandha every day?

Within studied durations (up to 3 months), daily use appears safe in healthy adults. Data beyond 3 months is sparse. Monitoring thyroid function is prudent for long-term use.

evidence

Ashwagandha: What the Evidence Actually Says About Stress and Cortisol

Multiple RCTs show ashwagandha reduces cortisol and perceived stress. This guide explains what the evidence shows, what it doesn't, and how to interpret the dosage research.

3 min read · 487 wordsReviewed May 2026

A cluster of white pills on a purple surface, highlighting pharmaceutical themes. - Evidence evidence guide for Ashwagandha: What the Evidence Actually Says About Stress and Cortisol — Photo by Anna Shvets on Pexels · Pexels License

Quick Answer

Ashwagandha (Withania somnifera) has moderate clinical evidence for reducing self reported stress and serum cortisol in chronically stressed adults. The most consistent results come from KSM 66 and Sensoril standardised extracts at 300–600 mg/day over 8–12 weeks.

Key Takeaways

01---
02Several randomised controlled trials have measured cortisol, stress scales (PSS), and anxiety measures. Key findings:
03A 2012 RCT in *Indian Journal of Psychological Medicine* (n=64) found 300 mg KSM-66 twice daily reduced PSS scores by 44% versus 5.5% for placebo.
04A 2019 RCT in *Medicine* (n=60) found Sensoril at 240 mg/day reduced cortisol by 22.2% after 60 days.
05A 2021 meta-analysis in *Journal of Ethnopharmacology* (7 RCTs, n=491) confirmed significant reductions in perceived stress and cortisol, with small-to-moderate effect sizes.

Quick Answer

Ashwagandha (Withania somnifera) has moderate clinical evidence for reducing self-reported stress and serum cortisol in chronically stressed adults. The most consistent results come from KSM-66 and Sensoril standardised extracts at 300–600 mg/day over 8–12 weeks.

What the Research Shows

Several randomised controlled trials have measured cortisol, stress scales (PSS), and anxiety measures. Key findings:

A 2012 RCT in Indian Journal of Psychological Medicine (n=64) found 300 mg KSM-66 twice daily reduced PSS scores by 44% versus 5.5% for placebo.
A 2019 RCT in Medicine (n=60) found Sensoril at 240 mg/day reduced cortisol by 22.2% after 60 days.
A 2021 meta-analysis in Journal of Ethnopharmacology (7 RCTs, n=491) confirmed significant reductions in perceived stress and cortisol, with small-to-moderate effect sizes.

Evidence Quality Assessment

Outcome	Evidence Level	Notes
Reduced perceived stress (PSS)	Moderate	Consistent across 5+ RCTs
Reduced serum cortisol	Moderate	15–30% reductions in stressed adults
Improved sleep quality	Preliminary	2 RCTs, small sample sizes
Testosterone increase in men	Preliminary	1 RCT, mixed quality
Athletic performance	Preliminary	Mixed results, endpoint variability

Most trials use proprietary extracts; generic root powder results may differ.

Standardisation Matters

Look for extracts standardised to withanolide content (the active compound class):

KSM-66: Root extract, 5% withanolides
Sensoril: Root + leaf extract, 10% withanolides
Generic "ashwagandha root powder": Variable withanolide content, limited trial data

Dosage Reference

Typical studied dose: 300–600 mg/day of standardised extract
Duration: 8–12 weeks to see stress and cortisol effects
Timing: Morning or split morning/evening; some trials use evening dosing for sleep endpoints

Safety Notes

Ashwagandha is generally well-tolerated at standard doses. Most common side effects are mild GI discomfort.
Thyroid conditions: Ashwagandha may increase thyroid hormone levels. People on thyroid medication should use caution and monitor levels.
Pregnancy: Avoid — traditionally considered abortifacient at high doses; no modern safety data exists.
Autoimmune conditions: Theoretical concern about immune stimulation; data is limited but worth flagging.
Rare cases of hepatotoxicity have been reported; causality is not established in most cases but warrants caution with pre-existing liver conditions.

What It Does Not Do (Yet)

There are no long-term trials (>6 months) in humans.
"Adrenal fatigue" as a clinical diagnosis is not validated by endocrinology consensus; ashwagandha should not be framed as treating it.
Effects on HPA axis dysregulation in clinical populations (not just stressed healthy adults) are understudied.

Practical Next Steps

Choose a KSM-66 or Sensoril product, 300–600 mg/day.
Take with food to reduce GI effects.
Assess stress and sleep after 8 weeks before deciding to continue.
Cycle off every 3 months if using long-term, until more longitudinal data is available.

FAQ

Frequently Asked Questions

Medically reviewed

Last reviewed May 9, 2026 by Migaku Editorial Team