Ashwagandha: Benefits, Dosage, Cycling & Huberman's Protocol

Ashwagandha (Withania somnifera) is an ancient Ayurvedic herb that has become one of the most popular supplements in the modern health optimization space. Classified as an adaptogen—a substance that helps the body adapt to stress—ashwagandha has been the subject of numerous clinical trials demonstrating benefits for cortisol reduction, anxiety, sleep quality, testosterone, and physical performance.

Andrew Huberman has discussed ashwagandha extensively on his podcast, noting both its significant benefits and the importance of cycling it rather than taking it continuously. In this guide, we cover everything you need to know.

What Makes Ashwagandha Work?

The active compounds in ashwagandha are withanolides, a group of steroidal lactones with anti-inflammatory, anti-anxiety, and hormone-modulating properties. The two most studied standardized extracts are:

• KSM-66: A full-spectrum root extract standardized to at least 5% withanolides. This is the most clinically studied ashwagandha extract, with over 24 "gold standard" clinical trials.
• Sensoril: An extract from both root and leaf, standardized to at least 10% withanolides. It may be slightly more sedating due to its different withanolide profile.

Proven Benefits of Ashwagandha

Cortisol and Stress Reduction

This is ashwagandha's most well-documented benefit. A 2012 double-blind, placebo-controlled study (PMID: 23439798) found that 300 mg of KSM-66 twice daily for 60 days reduced serum cortisol levels by 27.9% and significantly reduced scores on validated stress assessment scales. Participants reported meaningful improvements in anxiety, insomnia, and social functioning.

A 2019 study (PMID: 30854916) confirmed these findings, showing that 240 mg of ashwagandha extract daily reduced cortisol, perceived stress, and improved sleep quality over 60 days.

Anxiety

A 2014 systematic review of five randomized controlled trials (PMID: 25368499) concluded that ashwagandha significantly reduced anxiety scores compared to placebo across all included studies. The effect size was clinically meaningful and comparable to some anxiolytic medications.

Sleep Quality

Ashwagandha's species name, somnifera, literally means "sleep-inducing." A 2019 study (PMID: 31728244) found that 300 mg of ashwagandha root extract twice daily significantly improved sleep onset latency, sleep quality, and sleep efficiency compared to placebo, as measured by actigraphy (wrist-worn sleep tracker) and validated questionnaires. This makes it a potential complement to the Huberman sleep cocktail.

Testosterone and Male Reproductive Health

Multiple studies have demonstrated that ashwagandha can increase testosterone in men. A 2013 study (PMID: 24371462) in infertile men found that 5 g of ashwagandha root powder daily for 3 months increased testosterone by 10–22% and significantly improved semen quality. A 2015 study in healthy men doing resistance training (PMID: 26609282) found that 300 mg of KSM-66 twice daily increased testosterone and improved muscle strength and recovery.

The testosterone effect is thought to be partly mediated by cortisol reduction—high cortisol suppresses the hypothalamic-pituitary-gonadal (HPG) axis, and lowering cortisol removes this suppression.

Physical Performance

Beyond testosterone, ashwagandha has shown direct performance benefits. A 2015 study (PMID: 26609282) found significantly greater increases in muscle strength (bench press and leg extension) and muscle size, along with better exercise recovery and lower body fat percentage, in men supplementing with KSM-66 compared to placebo.

A 2012 study on VO2 max (PMID: 23326093) found that ashwagandha supplementation improved cardiorespiratory endurance in elite cyclists, suggesting benefits for both strength and endurance athletes.

Dosage: KSM-66 vs. Sensoril

KSM-66

KSM-66 ashwagandha is the most commonly recommended form. The standard dose is 300 mg twice daily (600 mg total), taken with meals. This is the dose used in most positive clinical trials. Some people take the full 600 mg at night for sleep benefits.

Sensoril

Sensoril ashwagandha is more concentrated (higher withanolide percentage), so the standard dose is 125–250 mg once or twice daily. Sensoril may be slightly more calming and is sometimes preferred for sleep and anxiety specifically. Studies have used 125 mg twice daily with positive results.

Timing

For stress and cortisol: take with breakfast and dinner (or both doses at dinner). For sleep: take the full dose 30–60 minutes before bed. For physical performance: take consistently every day, timing is less important.

Why You Should Cycle Ashwagandha

Andrew Huberman has specifically recommended cycling ashwagandha rather than taking it indefinitely. His reasoning:

1. Thyroid effects: Ashwagandha can increase thyroid hormone production (T3 and T4). While this may benefit people with subclinical hypothyroidism, continuous elevation of thyroid hormones in healthy individuals could be problematic. A 2018 case report documented thyrotoxicosis (excess thyroid hormone) in a woman taking ashwagandha (PMID: 29164659).
2. Emotional blunting: Some people report a reduction in emotional range with chronic use—less anxiety but also less excitement and motivation. This may relate to sustained cortisol suppression affecting the normal stress response.
3. Liver considerations: Rare case reports of liver injury associated with ashwagandha use have been published, though causality is difficult to establish. Cycling provides periodic breaks.

Recommended Cycling Protocol

The most common cycling pattern is:

• 8 weeks on, 2–4 weeks off
• Alternatively: 5 days on, 2 days off (weekday/weekend pattern)
• Or: 1 month on, 1 month off

There is no single "correct" cycling protocol. The key principle is to take periodic breaks rather than supplementing indefinitely.

Who Should Avoid Ashwagandha?

• People with hyperthyroidism — Ashwagandha may further elevate thyroid hormones.
• Pregnant or nursing women — Insufficient safety data. Some traditional sources classify it as an abortifacient at high doses.
• People on thyroid medication — May alter levothyroxine requirements. Consult your physician.
• Those on immunosuppressant drugs — Ashwagandha stimulates immune function, which could counteract immunosuppressive therapy.
• People on sedative medications — Additive sedative effects are possible.

Ashwagandha and the Bigger Picture

Ashwagandha works best as part of a comprehensive stress management approach. Combining it with adequate sleep, regular exercise, and a solid foundational supplement stack (see our beginner's stack guide) will produce the best results. For sleep specifically, ashwagandha pairs well with the magnesium, theanine, and apigenin stack discussed in our Huberman sleep cocktail article.

Frequently Asked Questions

How long does it take for ashwagandha to work?

Some people notice reduced anxiety within the first week, but the cortisol-lowering and testosterone-boosting effects typically take 4–8 weeks of consistent use to fully manifest. Clinical trials generally show statistically significant results at the 60-day mark.

Can women take ashwagandha?

Yes. While much of the testosterone research is in men, women benefit from ashwagandha's cortisol-lowering, anxiety-reducing, and sleep-improving effects. A 2012 study specifically in women (PMID: 23439798) included female participants and found significant benefits. Women should use the same dosing guidelines as men.

Can I take ashwagandha with caffeine?

Yes. Many people combine ashwagandha with their morning coffee. The calming effects of ashwagandha can offset some of the jitteriness from caffeine, creating a focused but calm state. This combination is popular in the nootropics community.

KSM-66 or Sensoril: which is better?

For general stress, testosterone, and performance: KSM-66 has more supporting research. For sleep and anxiety specifically: Sensoril may have a slight edge due to its calming profile. Both are effective. Choose based on your primary goal.

Does ashwagandha cause weight gain?

Ashwagandha does not directly cause weight gain. However, by reducing cortisol and improving sleep, it may improve appetite regulation and body composition. Some people gain lean mass (muscle) when combining ashwagandha with resistance training, which is a positive outcome.