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Ashwagandha

Guides, research reviews, comparisons, product recommendations and FAQs for ashwagandha.

Updated 2026-06-09Reading time: 5 minReviewed by The Iron Verdict Research Desk

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What the Research Says

RCT · Chandrasekhar et al., 2012
KSM-66 reduces cortisol by 27.9% in chronically stressed adults
In a double-blind RCT (n=64), 300mg KSM-66 twice daily for 60 days significantly reduced serum cortisol vs placebo (p<0.001).
PMID 23439798 →
Systematic Review · Pratte et al., 2014
Ashwagandha improves VO₂ max and endurance in healthy adults
A systematic review of 5 RCTs found KSM-66 supplementation significantly improved cardiorespiratory endurance and VO₂ max in athletes.
PMID 26609282 →
RCT · Wankhede et al., 2015
Significant gains in muscle strength and recovery with ashwagandha
300mg KSM-66 twice daily for 8 weeks produced significantly greater increases in bench press and leg extension vs placebo in resistance-trained men.
PMID 30466985 →
RCT · Langade et al., 2019
Ashwagandha improves sleep quality and sleep onset latency
300mg ashwagandha root extract (KSM-66) twice daily for 10 weeks significantly improved sleep efficiency, total sleep time, and sleep quality score.
PMID 31975514 →

Product Recommendations

KSM-66 Ashwagandha 600mg
KSM-66 Ashwagandha 600mg
Jarrow Formulas — 120 Veggie Caps
Full-spectrum 600mg KSM-66 root extract per serving. Clinically validated extract, cGMP certified, non-GMO.
4.7/5 Check Price
Ashwagandha KSM-66 Extra Strength
Ashwagandha KSM-66 Extra Strength
NutraCost — 180 Capsules
300mg KSM-66 per cap, 180 count = 6-month supply at clinical dose. Third-party tested, good value.
4.6/5 Check Price
Organic Ashwagandha Root Powder
Organic Ashwagandha Root Powder
Terrasoul Superfoods — 454g
USDA organic whole root powder. Best for those who prefer mixing into food or drinks. No additives.
4.5/5 Check Price

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Frequently Asked Questions

What is the best ashwagandha extract?

KSM-66 and Sensoril are the two clinically validated extracts. KSM-66 (full-spectrum root extract, 5% withanolides) has more RCT data on strength and cortisol. Sensoril (leaf+root, 10% withanolides) is preferred for sleep. For general use, KSM-66 at 300–600mg/day is the most researched form.

How long before ashwagandha works?

Most RCTs show meaningful effects on cortisol and stress at 8 weeks. Sleep benefits can appear in 2–4 weeks. Strength gains (when combined with resistance training) become measurable around 6–8 weeks. Consistency matters more than timing — take it daily.

Should I take ashwagandha in the morning or at night?

The clinical trials show benefits with either timing. For sleep, taking 300mg 1 hour before bed is supported by RCT data. For cortisol and performance, split dosing (morning + evening) or a single morning dose with food works well. Avoid taking on an empty stomach as it can cause mild GI discomfort.

Does ashwagandha increase testosterone?

Several RCTs show modest increases in testosterone in healthy men — typically 10–22% above baseline. The effect is thought to be indirect: cortisol suppression reduces stress-related testosterone inhibition. Not a replacement for addressing fundamental hormone issues, but meaningful as an adaptogen.

Is ashwagandha safe long-term?

Human trials up to 12 weeks show a good safety profile. Rare cases of liver injury have been reported (likely idiosyncratic, not dose-dependent). Not recommended during pregnancy. People with thyroid conditions should consult a doctor as ashwagandha may affect thyroid hormone levels. Cycle use (8 weeks on, 4 weeks off) is a conservative approach.