Ashwagandha is everywhere: in gym stacks, “sleep” gummies and testosterone boosters. Some of the research is genuinely interesting, but much of the marketing goes well beyond the evidence. This guide looks at what the trials on ashwagandha for men actually show, how strong that evidence is, and the safety questions you should know about before trying it.
Key takeaways
- Ashwagandha (Withania somnifera) is a traditional Ayurvedic herb, sold today mostly as root or root-and-leaf extracts.
- Small, short trials suggest modest benefits for perceived stress and sleep quality. Most were done in India, several tested branded extracts, and the NIH describes most trials as small and short.
- A handful of trials in men report gains in strength and testosterone, but the numbers are small and results vary.
- Doses studied mostly range from about 225 to 600 mg of extract per day, for 6 to 12 weeks.
- Safety concerns include rare liver injury, effects on thyroid hormones, drug interactions and pregnancy. Denmark banned it in food supplements in 2023, and several other regulators have issued warnings.
What is ashwagandha?
Ashwagandha is a small shrub in the nightshade family that has been used in Ayurvedic medicine for centuries. It is often described as an “adaptogen”, a marketing-friendly term for substances said to help the body cope with stress. That label isn’t a recognized medical category, so it’s better to judge ashwagandha on specific outcomes: stress, sleep, strength and hormones.
Products differ widely. Some use only the root, some use root and leaf, and extracts are standardized to different amounts of withanolides (the compounds thought to be active). This matters, because a result from one extract doesn’t automatically apply to another.
How good is the evidence?
Before looking at individual results, keep these limitations in mind. The NIH Office of Dietary Supplements (ODS) notes that:
- Most trials are fairly small and short, usually 6 to 12 weeks.
- Products and doses vary a lot, which makes firm recommendations difficult.
- Many studies were carried out in India within traditional medicine settings, so it’s unclear how well results apply elsewhere.
- Research on sleep is described as limited.
Several of the best-known trials tested branded extracts, and some review authors have disclosed ties to supplement makers. That doesn’t make the findings wrong, but it’s a reason to be cautious and to want independent replication.
Stress and cortisol
This is the most studied area. According to the NIH ODS, a 2021 systematic review of seven studies in 491 adults (all in India) found that ashwagandha improved scores for stress, anxiety, sleeplessness and fatigue, and lowered blood cortisol compared with placebo over 6 to 8 weeks.
One early, widely cited trial (Chandrasekhar and colleagues, 2012) gave 64 adults with chronic stress 600 mg a day of a root extract for 60 days and reported a 27.9 percent drop in serum cortisol. Other trials have reported lower cortisol with doses between 225 and 300 mg a day.
Results aren’t uniform. In a 12-week trial of 120 adults with overweight or mild obesity, 400 mg a day did not reduce perceived stress compared with placebo, although fatigue scores improved.
Bottom line: there is reasonable, though limited, evidence for a modest reduction in self-reported stress over a couple of months. It is not a replacement for addressing the causes of stress, or for treating an anxiety disorder with a professional.
Sleep
The NIH ODS summarizes a 2021 meta-analysis of five studies (372 adults, 6 to 12 weeks) that found a small but significant improvement in sleep. Benefits looked stronger at around 600 mg a day, in people with insomnia, and with at least 8 weeks of use.
Individual trials include one in 150 adults with insomnia symptoms (120 mg a day of a root-and-leaf extract for 6 weeks), where 72 percent of the ashwagandha group reported better sleep quality compared with 29 percent of the placebo group, and another in 80 adults (600 mg a day for 8 weeks) that found improvements in sleep quality and time to fall asleep among those with insomnia.
Bottom line: the effect looks small. For chronic insomnia, CBT-I is the recommended first-line treatment, and the habits in our guide on how to sleep better after 35 will likely do more than any supplement.
Strength, recovery and training
A 2015 trial in the Journal of the International Society of Sports Nutrition gave 57 young men (around 28 years old, 50 completed the study) either 600 mg a day of root extract or placebo during 8 weeks of supervised resistance training. The ashwagandha group improved more on bench press (about 46 kg versus 26 kg) and leg extension (about 14.5 kg versus 9.8 kg), and had larger increases in testosterone from baseline. Notably, final testosterone levels between groups were not statistically different.
A 2021 Bayesian meta-analysis of 12 studies (615 healthy men and women) concluded that ashwagandha outperformed placebo for strength and power and for fatigue and recovery. Its estimate for cardiorespiratory fitness was more uncertain. The authors flagged the small number of studies, results that were sensitive to which studies were included, and that two authors had industry ties.
Bottom line: possible modest benefit, but the effect sizes come from a small set of trials. Training, protein and sleep matter far more. If you want a well-proven performance supplement, the evidence for creatine is much stronger. And no supplement replaces a solid strength training program.
Testosterone
This is the claim that sells the most product. The evidence:
- A 2019 crossover trial in the American Journal of Men’s Health enrolled 57 overweight men aged 40 to 70 with mild fatigue (43 completed both phases). Over 8 weeks, a standardized extract raised testosterone 14.7 percent more than placebo and DHEA-S 18 percent more. However, fatigue and vigor did not improve significantly compared with placebo.
- A 2021 systematic review in Advances in Nutrition looked at 32 trials of 13 herbs and concluded that ashwagandha and fenugreek showed positive effects on testosterone in men. It also noted small samples, mixed preparations and that only 6 of the 32 trials had low risk of bias.
Bottom line: some trials show a modest rise in testosterone, but in a small number of mostly healthy men, and it’s unclear how much that matters for how you feel or perform. If you think your testosterone is low, see a doctor for proper testing rather than self-treating. Our guide to testosterone after 35 explains the lifestyle factors that matter most.
Doses used in research
| Outcome studied | Daily doses used in trials | Typical duration | Strength of evidence |
|---|---|---|---|
| Stress and cortisol | About 225–600 mg extract (benefits looked greater at 500–600 mg) | 4–12 weeks | Moderate-low: several small RCTs, mostly in India |
| Sleep | 120 mg (root-and-leaf extract) to 600 mg (root extract) | 6–12 weeks | Low: small effect, limited research |
| Strength and recovery | Most commonly 600 mg root extract | 8–12 weeks | Low: few small trials, some with industry links |
| Testosterone | 600 mg root extract in one trial; another used an extract standardized to 21 mg withanolide glycosides | 8–16 weeks | Low: few trials, modest changes |
These are research doses, not a recommendation. Products vary in what they contain, and studies rarely ran longer than three months. Check with your doctor before taking ashwagandha, especially if you take any medication.
Safety: what you need to know
In trials lasting up to about three months, ashwagandha has generally been well tolerated, with mild side effects such as stomach upset, loose stools, nausea and drowsiness. Long-term safety is not known. Beyond that, there are several real concerns.
Liver injury
The NIH ODS notes that ashwagandha has been linked to liver injury in some people. A 2020 case series from Iceland and the U.S. Drug-Induced Liver Injury Network described five people who developed jaundice 2 to 12 weeks after starting ashwagandha. None developed liver failure and liver tests normalized within months in most, but the injuries were significant. Cases are rare, product contents weren’t always verified, and some involved combination products. Stop and see a doctor immediately if you develop yellow skin or eyes, dark urine, itching or abdominal pain.
Thyroid
Ashwagandha may change thyroid hormone levels. Small studies have shown increases in T4 and T3, and there are case reports of thyrotoxicosis (an overactive thyroid state) that resolved after stopping. If you have a thyroid condition or take thyroid medication, don’t use it without your doctor’s input.
Interactions and who should avoid it
- Possible interactions with thyroid medication, diabetes medication, blood pressure medication, sedatives and immunosuppressants.
- Not recommended during pregnancy or breastfeeding. Australia requires a pregnancy warning on some ashwagandha products.
- May not be safe for men with hormone-sensitive prostate cancer, because of possible effects on testosterone.
- People with liver disease or autoimmune conditions should talk to their doctor first.
Regulatory restrictions
Regulators have become more cautious. Denmark commissioned a risk assessment published in 2020 that concluded there wasn’t enough evidence to set a safe intake level, and it banned ashwagandha in food supplements in 2023. France’s food safety agency (ANSES) has advised against use in pregnant and breastfeeding women and people with certain conditions. The Netherlands advised against use in 2024, Sweden and Finland have investigated, and the UK Food Standards Agency launched a call for evidence in 2024. In India, the Ministry of Ayush has issued advisories against using the leaves, which have been challenged in court. Rules depend on where you live, and they are changing.
Safety note: Don’t take ashwagandha if you are pregnant, breastfeeding or have hormone-sensitive prostate cancer. Talk to your doctor first if you have a thyroid, liver or autoimmune condition, or take thyroid, diabetes, blood pressure, sedative or immune-suppressing medication. Stop and get medical help if you notice yellowing of the skin or eyes, dark urine, itching or abdominal pain. Supplements are not regulated like medicines, so product contents can vary.
Should you try it?
If you’re a healthy man with no relevant conditions or medications, your doctor agrees, and you’ve already fixed sleep, alcohol, training and diet, a short trial at a researched dose is a reasonable experiment. Judge it honestly after 8 weeks, and don’t take it indefinitely.
If you’re stressed, sleeping badly and tired all the time, start with the fundamentals. Our guide to feeling always tired after 35 covers the common causes worth ruling out first.
FAQ
Does ashwagandha increase testosterone?
A few small trials report modest increases, mostly in healthy men. The quality and number of studies is limited. It is not a treatment for low testosterone. See a doctor for proper testing.
How long does ashwagandha take to work?
Most trials ran 6 to 12 weeks. Sleep benefits appeared more clearly after about 8 weeks. If you notice nothing after two months, it’s probably not doing much for you.
Is ashwagandha safe to take long term?
No one knows. Most studies lasted three months or less. Rare liver injury and thyroid effects have been reported, which is why some countries restrict it.
Can I take ashwagandha with creatine or protein?
There is no known interaction with creatine or protein powder. The main concerns are with medications (thyroid, diabetes, blood pressure, sedatives, immunosuppressants). Check with your doctor or pharmacist.
Is ashwagandha legal?
It depends on where you live. Denmark banned it in food supplements in 2023, and other countries have issued warnings or are reviewing it. Check your local rules.
Free tool: fix the basics first: find your bedtime and caffeine cut-off with the sleep calculator.
Sources
- NIH Office of Dietary Supplements: Ashwagandha fact sheet for health professionals
- NIH Office of Dietary Supplements: Ashwagandha fact sheet for consumers
- NutraIngredients: Report on Chandrasekhar et al. (2012), Indian Journal of Psychological Medicine
- Wankhede et al. (2015): Withania somnifera supplementation on muscle strength and recovery, JISSN
- Bonilla et al. (2021): Effects of ashwagandha on physical performance, systematic review and Bayesian meta-analysis
- Lopresti et al. (2019): Ashwagandha in aging, overweight males, American Journal of Men’s Health
- Smith et al. (2021): Examining the effects of herbs on testosterone concentrations in men, Advances in Nutrition
- Björnsson et al. (2020): Ashwagandha-induced liver injury, case series from Iceland and the US DILIN
- NutraIngredients (2026): Timeline of regulatory action on ashwagandha
This article is for general education and is not medical advice. Check with your doctor before starting a new training or nutrition plan, especially if you have a health condition.
