# Ashwagandha: Cortisol, Testosterone & How Long It Takes to Work
Canonical: https://www.migaku.app/guides/ashwagandha-complete-guide
Category: how-to
Summary: Which ashwagandha extract, how much, how long — cortisol reduction, testosterone, and sleep evidence.
Last reviewed: 2026-04-05
Reviewed by: Migaku Editorial Team
## Quick Answer

Ashwagandha (KSM-66 or Sensoril extract, 300–600 mg daily) reduces cortisol by 15–30%, improves stress resilience within 4 weeks, and increases testosterone in men with subfertility or under chronic stress. Effects on anxiety appear earlier (1–2 weeks); testosterone and body composition changes require 8–12 weeks.

## Key Takeaways

- KSM-66 (root only) and Sensoril (root + leaf) are the only extracts with robust human clinical data
- Withanolides are the primary bioactive compounds — look for extracts standardised to at least 5%
- Works best in people with high baseline cortisol — those under significant stress
- Safe for long-term use in most adults; cycle 8 weeks on, 2–4 weeks off as a precaution
- Avoid if pregnant, have thyroid disease, or take immunosuppressants

## Cortisol Reduction: The Evidence

A 2012 double-blind RCT (Indian Journal of Psychological Medicine): 64 adults with chronic stress received KSM-66 300 mg twice daily for 60 days.

Results:
- Serum cortisol: −27.9% vs −7.9% in placebo group
- Perceived Stress Scale scores: −44% vs −5.5%
- Anxiety and insomnia scores: significantly improved
- Adverse events: no difference from placebo

## Testosterone: What the Evidence Shows

Ashwagandha's testosterone effects are documented specifically in:
- **Men with subfertility**: 675 mg/day for 90 days → 17% increase in testosterone, 167% increase in sperm count (Fertility and Sterility, 2010)
- **Overweight men under resistance training**: 300 mg twice daily → 15% testosterone increase vs control (J. Int. Society Sports Nutrition, 2015)
- **General healthy men**: Smaller, less consistent effects — likely because cortisol suppression of LH/testosterone is the mechanism

If you are not under significant stress and have normal testosterone, effects will be modest.

## Dosing Protocol

**For stress and cortisol:**
- KSM-66: 300 mg AM + 300 mg PM (or 600 mg once, evening)
- Minimum effective trial: 4 weeks; full effects at 8–12 weeks

**For testosterone support:**
- 675 mg KSM-66 daily (300 mg AM + 375 mg PM)
- 12 weeks minimum for spermatogenic effects

**For sleep:**
- Sensoril 250–300 mg, 60 minutes before bed (leaf compounds have stronger sedative profile)

## Ashwagandha vs Rhodiola

| Property | Ashwagandha | Rhodiola |
|-----------|-------------|---------|
| Speed of action | Slow (4–8 weeks) | Fast (single dose for acute fatigue) |
| Primary mechanism | HPA axis regulation | Monoamine modulation |
| Best for | Chronic stress, sleep, testosterone | Acute fatigue, burnout, mental performance |
| Stimulating? | Mildly calming | Mildly stimulating |