Ashwagandha root: benefits and rare side effects reviewed
What it found
In people, ashwagandha root improved sleep, stress, anxiety, muscle strength, testosterone and immune markers in many trials, and side effects were rare.
A few case reports described liver injury, mostly with unclear products or other herbs.
What they found
Studies in people
Stress, anxiety and sleep
In several placebo-controlled trials in people, ashwagandha root extract reduced stress, anxiety and insomnia, and lowered cortisol. Improvements were seen after 8 to 12 weeks.
Muscle strength and oxygen
In athletes and healthy adults, ashwagandha improved muscle strength, recovery and maximal oxygen uptake. A meta-analysis concluded it was better than placebo for physical performance.
Testosterone and fertility
In men, ashwagandha increased testosterone levels modestly, by up to 15%, and improved sperm count and motility in some studies. Levels stayed within the normal range.
Thyroid function
In people with mild hypothyroidism, ashwagandha normalized thyroid hormones. In people with normal thyroid function, up to 2000 mg daily for 3 months did not push thyroid hormones outside the normal range.
Liver injury reports
A small number of case reports described liver injury, with symptoms like jaundice and elevated liver enzymes, after taking ashwagandha. Most cases resolved after stopping, but one person needed a liver transplant.
Animal and lab studies
Liver protection in animals
In animal studies, ashwagandha protected the liver from damage caused by paracetamol, gentamicin and other substances, and improved antioxidant levels. No liver toxicity was seen in animals given high doses.
What the authors conclude
“In general, it should be noted that side effects with ashwagandha are rare. Indeed, the levels reported so far in clinical trials are comparable to what would be seen with a placebo.”
Also in their conclusions
- They conclude that ashwagandha root powder or extracts can improve the immune system, sex hormones, oxygen uptake, muscle strength, stress, anxiety, sleep and cognitive function.
- They state that side effects are rare and comparable to placebo in clinical trials, but a few cases of liver injury have been reported.
- They advise that more long-term studies are needed to clarify safety and efficacy.
How it was done
The authors wanted to evaluate the scientific evidence on ashwagandha's benefits and side effects, and to highlight gaps for new research. They note that millions take it daily, yet few side effects have been reported.
They reviewed scientific studies on ashwagandha from 1994 onward, including lab tests, animal studies and human clinical trials. The review covered many health areas, such as stress, sleep, muscle strength, hormones and liver safety.
What it can’t tell you
- Most clinical studies lasted only 1 to 3 months, so the effects of taking ashwagandha for years are not known.
- The case reports of liver injury often involved unclear products, other herbs or medicines, so a clear cause and effect cannot be established.
- Animal and lab results may not reflect what happens in people.
Who paid
- Conflicts
- The author declares no conflicts of interest.
- Authors work at
- University of Copenhagen, Denmark
The paper
- Title
- The Clinical Implications of Ashwagandha ( Withania somnifera L.) with a Special Reference to Side Effects-A Review
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Winther K (2026). The Clinical Implications of Ashwagandha ( Withania somnifera L.) with a Special Reference to Side Effects-A Review. Nutrients. doi:10.3390/nu18050871Free full textPubMed 41830041DOI
Summary written 29 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error