Ashwagandha (KSM-66 / root extract)
- Effective dose
- 250–600 mg
- Evidence
- 3/5· Moderate
Last updated June 1, 2026
What it is
Ashwagandha (Withania somnifera) is an adaptogenic herb used in Ayurvedic tradition, with standardized root extracts such as KSM-66 most studied. It appears to modulate the stress response, including lowering cortisol, which underlies its reputation as a stress and anxiety supplement.
Benefits
Randomized trials of standardized root extract show reductions in perceived stress, anxiety, and serum cortisol, with some evidence for better sleep. Effective doses are about 250-600 mg/day of standardized root extract, with the 600 mg/day dose used in several well-controlled stress studies over 8 weeks.
When to take it
Taken daily, often split or in the evening given its calming and sleep-supporting effects; most studied over 8-12 week periods.
Side effects
Generally well tolerated short-term; mild GI upset and drowsiness can occur. Rare reports of liver injury exist, it may affect thyroid hormones, and it is not advised in pregnancy or alongside certain medications without medical guidance.
Sources
Products containing Ashwagandha (KSM-66 / root extract)
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