Ashwagandha

Also called Withania somnifera, Indian ginseng.

Dr Chad OkayFounder, Suna Health

3 min read. Updated .

Ashwagandha is a herb traditionally used in Ayurvedic medicine, marketed in the West as an adaptogen for stress, sleep and anxiety. Small trials of standardised extracts over 8 to 12 weeks show modest reductions in cortisol and self-reported stress. It interacts with thyroid medication, is not advised in pregnancy, breastfeeding or active autoimmune disease, and carries published case reports of liver injury. Regulators are actively reviewing its safety: the UK Food Standards Agency has an open review, and Denmark has banned it in supplements.

What the evidence shows

  • Reduces self-reported stress and anxiety in 8 to 12 week trials (modest pooled effect versus placebo; the trials are small and mostly short).
  • Lowers morning cortisol in stressed populations (roughly 25 to 30% in small placebo-controlled trials; Chandrasekhar 2012 measured 27.9%).
  • Improves sleep onset and quality in some studies.
  • May modestly improve testosterone and strength in men in trials with active resistance training.
  • Most evidence is from KSM-66 or Sensoril extract formulations, not raw root powder.

What the trials used

  • Most trials used 250 to 600 mg a day of a standardised extract, usually in the evening, for 8 to 12 weeks. That is a description of the studies, not a dose to copy: the UK has no established safe level for ashwagandha in supplements, and the Food Standards Agency's review is ongoing.
  • If you are considering it, talk to a pharmacist first, especially if you take any regular medication. If nothing has changed after about 8 weeks, the trials give no reason to continue.
  • Most of the evidence comes from two branded standardised extracts rather than raw root powder, so results with other products may differ.

Where regulators stand

  • Denmark banned ashwagandha in food and supplements in 2023, citing possible effects on thyroid and sex hormones, pregnancy and the liver. Industry and some academics dispute the assessment.
  • The UK Food Standards Agency ran a call for evidence in 2024 and its independent toxicity committee is reviewing the safety data. No UK safe level has been set.
  • An EU working group prioritised ashwagandha for formal safety assessment in 2024.
  • None of this proves harm at typical supplement amounts, but it is why the caution around this herb is higher than its shelf position suggests.

Who should not take it

  • Pregnancy and breastfeeding (insufficient safety data, and Denmark's assessment raised concern about use in pregnancy).
  • Active autoimmune disease (NCCIH advises against use in autoimmune disorders).
  • Hyperthyroidism or on levothyroxine for hypothyroidism (can shift thyroid hormones).
  • Existing liver disease, heavy alcohol use, or medicines that stress the liver (published case reports of liver injury, catalogued in LiverTox).
  • Scheduled surgery within 2 weeks (mildly sedating).
  • Sensitivity to nightshade family plants (rare cross-reaction).

Reported side effects

  • Mild stomach upset (most common, usually settles in a week).
  • Drowsiness during the day.
  • Rare: liver injury (case reports catalogued in LiverTox). Stop immediately and see a doctor urgently if you develop jaundice, dark urine or pain under the right ribs.
  • Vivid dreams reported anecdotally by some users.

Common questions

Will ashwagandha help my anxiety as much as therapy or medication?
No. Effect size is modest. Useful as part of a broader stress-management approach (sleep, exercise, therapy). Severe anxiety needs more direct treatment.
Is it safe long-term?
8 to 12 weeks of continuous use is well-studied. Some people cycle on for 8 weeks, off for 2. Multi-year continuous use has less evidence; periodic breaks are sensible.
Does it actually lower cortisol?
Modestly, in chronically stressed populations. Roughly 25 to 30% reduction in morning cortisol in small placebo-controlled trials (Chandrasekhar 2012: 27.9%). The clinical relevance of this is debated.
Why does my ashwagandha bottle warn about liver issues?
Case reports of ashwagandha-associated liver injury have appeared since around 2017 (catalogued in NIH's LiverTox database, with growing case-series since). Most resolve on stopping. The risk is small but real. If you develop jaundice, dark urine or right-upper abdominal pain, stop and see a doctor.

Sources

Written by Dr Chad Okay. Contributor: Dr Parisah Hussain, MBChB, BSc (Hons), DRCOG, MRCGP. Last updated 10 September 2026. From Digests.

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