Short answer: ashwagandha has reasonable short-term trial evidence for reducing self-reported stress and anxiety, typically at 300–600 mg per day of a root extract standardised to withanolides. Long-term safety is not well established, there are reports of liver injury, and several groups should avoid it entirely.
Ashwagandha is the adaptogen with the most human data behind it, which makes it worth taking seriously in both directions — the evidence and the cautions.
Standardisation is the whole question
‘Ashwagandha’ on a label can mean very different things. Trials generally use root extracts standardised to a stated withanolide percentage. A raw powder, a leaf-inclusive extract and a standardised root extract are not interchangeable.
If a label says only ‘ashwagandha 500 mg’ with no part of plant and no standardisation, you cannot map it onto any trial. That is the most common problem with this ingredient on the shelf.
What the evidence supports
The strongest signal is for reductions in self-reported stress and anxiety over roughly eight weeks. Some trials also report improved sleep quality. Effects on testosterone, strength and cognition have been studied but the evidence is thinner and less consistent.
- Most trials are short — typically eight to twelve weeks.
- Outcomes are largely self-reported questionnaires rather than objective measures.
- Several trials are industry-funded, which does not invalidate them but does warrant caution.
The safety issues that get skipped
There are documented reports of liver injury associated with ashwagandha products. It is uncommon, but it is real, and it is rarely mentioned in marketing. Stop and seek medical advice for jaundice, dark urine, persistent nausea or abdominal pain.
Ashwagandha may also increase thyroid hormone levels, which matters for anyone with thyroid disease or on thyroid medication, and it may have immunostimulant effects relevant to autoimmune conditions.
Who should avoid it
- Anyone pregnant — traditional use includes abortifacient properties, and it is contraindicated.
- People with thyroid conditions or on thyroid medication, without clinician supervision.
- People with autoimmune conditions, or on immunosuppressants.
- Anyone with existing liver disease.
- Anyone scheduled for surgery, because of sedative effects.
Frequently asked questions
What does ‘standardised to withanolides’ mean?
It means the extract has been produced to contain a stated percentage of withanolides, the marker compounds. It lets you compare a product against the extracts used in trials.
How long before ashwagandha does anything?
Trials reporting benefit generally run eight weeks or more. It is not an acute effect you would notice on day one.
Is ashwagandha safe to take long term?
Long-term safety is not well established. Most trials are short, and given the liver-injury reports, indefinite use without medical oversight is not well supported.
Sources
- National Center for Complementary and Integrative Health — Ashwagandha: What You Need To Know (including liver safety).
- LiverTox, National Institute of Diabetes and Digestive and Kidney Diseases — clinical and research information on drug-induced liver injury.
Medical disclaimer. This article is general information, not medical advice, and cannot account for your history, medication or symptoms. Speak to a doctor or pharmacist before starting any supplement. Read our full disclaimer.