Ashwagandha (Withania somnifera) is a shrub used in Ayurvedic medicine for thousands of years. In the West it’s sold as an “adaptogen” — a substance said to help the body cope with stress.
What the research shows
Stress and anxiety. A number of small randomized trials, mostly lasting 6–12 weeks, have found that ashwagandha root extract reduced self-reported stress and anxiety and, in some, lowered cortisol levels compared with placebo. The studies are generally small, short and often funded by manufacturers, so the evidence is considered promising but not definitive.
Sleep. Several trials report modest improvements in sleep quality and time to fall asleep. Again, the studies are small.
Other claims — for strength, testosterone, fertility and thyroid function — have very limited evidence.
Doses used in studies
Trials have typically used standardized root extracts in the range of 250–600mg per day. Products vary widely, so look for a standardized extract with the dose clearly stated.
Safety
Ashwagandha seems well tolerated in short-term studies, with mild side effects such as stomach upset and drowsiness. But there are important cautions:
- Liver injury. There are case reports of liver damage linked to ashwagandha supplements. It’s considered rare, but stop and see a doctor if you develop dark urine, yellowing skin or eyes, or abdominal pain.
- Thyroid. Ashwagandha may raise thyroid hormone levels. People with thyroid conditions or on thyroid medication should check with a clinician.
- Pregnancy. It should be avoided during pregnancy.
- Interactions. It may interact with sedatives, immunosuppressants and medications for diabetes, blood pressure and thyroid.
Long-term safety beyond a few months isn’t well studied. Some countries have restricted or reviewed ashwagandha products because of safety concerns.
The bottom line
Ashwagandha may help some people with stress and sleep, but the evidence is limited and it isn’t risk-free. Choose a third-party tested product, use it for a defined trial period, and check with a clinician — especially if you have a thyroid or liver condition or take medication.