Supplement analysis backed by scientific evidence · PT · ES · DE · FR

← All supplements
Moderate evidenceStress & mood

Ashwagandha

An adaptogenic herb from Ayurvedic medicine. Studies point to reduced stress, anxiety, and cortisol, but the trials are still small.

View on iHerb Ships to 180+ countries · welcome discount for new customers

What the science says

  • Reduced stress and anxiety Moderate evidence

    Randomized controlled trials showed significant reductions in perceived stress scores and serum cortisol with root extract (e.g. 300 mg twice daily of KSM-66 extract). The studies are positive but small and often industry-funded.

  • Improved strength and performance Limited evidence

    A few small studies suggest gains in strength and VO2max, but the evidence is still insufficient for a firm recommendation.

Dosage & safety

Studied dose300–600 mg/day of standardized root extract (with withanolides), usually split into two doses.
SafetyWell tolerated in short-term use (up to ~3 months in studies). Rare reports of liver toxicity. Avoid during pregnancy and in thyroid disease without medical supervision.

How to take it

TimingSplit morning and evening, or take the whole dose in the evening if it makes you drowsy.
With food?With food — nausea and stomach upset on an empty stomach are the usual reason people abandon it.
Worth knowingInsist on a stated withanolide percentage; 'root extract' with no standardisation tells you nothing about what is in the capsule.

Interactions

With medications

  • levothyroxine and other thyroid hormone

    Ashwagandha can raise thyroid hormone levels; case reports describe thyrotoxicosis, and it can push someone on replacement into overtreatment. avoid in thyroid disease or on thyroid medication without endocrinology input

  • benzodiazepines, z-drugs and other sedatives

    Additive central nervous system depression. do not combine without medical advice

  • immunosuppressants (ciclosporin, tacrolimus, azathioprine)

    Ashwagandha has immunostimulant activity that may oppose the drug's purpose. avoid unless your transplant or rheumatology team approves

  • antidiabetic and blood pressure medication

    Modest additive lowering of glucose and blood pressure. monitor when starting, and watch for lightheadedness or hypoglycaemia

With other supplements

  • melatonin, valerian and other sedating supplements

    Additive drowsiness. start one at a time rather than in a stack

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does ashwagandha work for stress and anxiety?

The evidence for ashwagandha is moderate: randomized trials show significant drops in perceived stress and serum cortisol with root extract, such as 300 mg twice daily of KSM-66. The studies are positive but small and often industry-funded.

How much ashwagandha per day?

Take 300–600 mg/day of a standardized ashwagandha root extract, usually split into two doses and with food to avoid stomach upset. Choose an ashwagandha product that states its withanolide percentage.

Is ashwagandha safe with thyroid medication?

Not without specialist input. Ashwagandha can raise thyroid hormone levels, and case reports describe thyrotoxicosis, so avoid ashwagandha in thyroid disease or on levothyroxine without endocrinology advice.

Is ashwagandha safe to take every day?

Ashwagandha has been well tolerated in studies lasting up to about 3 months, but there are rare reports of liver toxicity. Avoid ashwagandha during pregnancy.

Scientific references

Where to buy

Swanson Vitamins, Full Spectrum® Ashwagandha, 450 mg, 100 Vegan Capsules

View on iHerb

Ships to 180+ countries · welcome discount for new customers

Referral link — this site may earn a commission on purchases.

Related in Stress & mood