Ashwagandha, measured against the trials
Ashwagandha (Withania somnifera) is the most-studied adaptogen in the supplement aisle. This guide covers what randomised trials actually measured, the doses they used, how extracts differ, when to take it, and who should not.
Studied for perceived-stress and cortisol measures.
Trials report improved sleep-onset and quality scores.
Withanolide content is what makes a dose comparable.
What ashwagandha is
Ashwagandha is a root used in Ayurvedic practice, now sold mostly as a standardised root extract. Withanolides are the marker compounds, and a credible label states both the extract ratio and the withanolide percentage. Branded extracts such as KSM-66 and Sensoril are simply well-characterised versions with their own trial data and different withanolide profiles.
Root-only extracts are the norm in the clinical literature; leaf material has a different profile and is not interchangeable.
What the trials measured
Randomised, placebo-controlled trials have repeatedly measured perceived-stress scales and salivary or serum cortisol over 8 to 12 weeks, generally finding improvements against placebo. Smaller studies look at sleep quality, exercise performance and testosterone in men, with more variable results.
These are quality-of-life measures in generally healthy adults. Ashwagandha is not a treatment for anxiety disorders, depression or insomnia, and it does not replace care for those conditions.
Dosage and best time to take it
Most trials use 300 to 600 mg of standardised root extract per day, taken once or twice with food. Whole-root powder doses are far higher because they are unconcentrated — which is why comparing milligrams across formats is meaningless without the extract ratio.
For stress through the day, morning with breakfast suits most people. For sleep, evening. Both are reasonable; pick one and hold it for at least four weeks.
Who should avoid it
Skip ashwagandha if you are pregnant or breastfeeding. Speak to a clinician first if you have thyroid disease, an autoimmune condition, or take sedatives, thyroid medication or immunosuppressants. Rare reports of liver injury exist, so stop and seek advice if you notice unusual fatigue, dark urine or yellowing skin.
As with any adaptogen, more is not better. Stay at the label serving.
Common questions
- What does ashwagandha do?
- Ashwagandha is an adaptogenic root extract studied mainly for stress and sleep. Randomised trials in healthy adults report improvements in perceived-stress scores and cortisol measures over 8 to 12 weeks, with smaller studies looking at sleep quality and exercise performance.
- How much ashwagandha should I take daily?
- Clinical trials most often use 300 to 600 mg of standardised root extract per day, taken once or twice with food. Follow the label serving of the specific extract you own, since concentrations differ.
- Is it better to take ashwagandha in the morning or at night?
- Both work. Morning with food suits people using it for daytime stress; evening suits people focused on sleep. Consistency over four or more weeks matters more than the hour.
- How long does ashwagandha take to work?
- Most trials measure change at 8 to 12 weeks, and many people report noticing something within two to four weeks of daily use. It is cumulative, not immediate.
- Who should not take ashwagandha?
- Avoid it if you are pregnant or breastfeeding. Check with a clinician first if you have thyroid or autoimmune disease, or take sedatives, thyroid medication or immunosuppressants.
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