Ashwagandha
Summary
Ashwagandha is an Ayurvedic herb sold as root or root-and-leaf extracts. Meta-analyses of mostly small, short trials report lower perceived stress (grade B) and better sleep (grade B), with low certainty and large differences between extracts. It appears well tolerated for about 3 months; rare liver injury and thyroid effects are reported.
Key facts
- Root extracts (e.g., KSM-66), root-and-leaf extracts (e.g., Shoden, Sensoril) and whole root powder; withanolide content differs by extract[1]
- Perceived stress ↑ improved (B); sleep ↑ improved, small effect (B); anxiety scores ↑ (C); strength with training ↑ (C)[2][4][3][6]
- 120–1,250 mg/day of extract; one trial used 6 g/day root powder[1]
- 6 to about 13 weeks; long-term safety unknown[1]
- None (botanical)[1]
- Thyroid hormone, antidiabetes, blood pressure, immunosuppressant and sedative medicines[1]
- 3 meta-analyses and 3 randomized trials, plus 1 meta-analysis and 3 trials cited as supporting evidence[2][3][4][5][6][7][8][9][12]
- 6 graded human outcomes on this page
- October 9, 2026
How it works
ProposedWithanolides (steroidal lactones) are thought to drive many effects, though non-withanolide compounds may contribute (proposed, mostly from preclinical work). Lower morning cortisol in trials suggests an effect on the stress-hormone (HPA) axis (proposed).[1][5]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Stress | Grade B | Improved | Meta-analysis · n = 1,002 · 2022 | 3 rows |
| Sleep | Grade B | Improved | Meta-analysis · n = 400 · 2021 | 1 row |
| Performance | Grade C | Improved | RCT · n = 57 · 2015 | 1 row |
| Energy | Grade C | No effect | Crossover RCT · n = 57 · 2019 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Perceived stress | Improved | Grade B | Meta-analysis · n = 1,002 · 2022 12 RCTs, adults aged 25–48 Form: ashwagandha extracts (various) · Dose: Varied; dose-response analysis favored 300–600 mg/day for stress · Duration: Varied across trials Stress (SMD -1.75) and anxiety (SMD -1.55) fell versus placebo. Heterogeneity was very high (I² 83–94%) and certainty of evidence was low. | 36017529 (opens PubMed)Source [2] |
| Overall sleep | Improved | Grade B | Meta-analysis · n = 400 · 2021 5 RCTs in adults, healthy or with insomnia Form: ashwagandha extract (root, or root-and-leaf in one trial) · Dose: Varied; larger effect at ≥600 mg/day · Duration: Varied; larger effect at ≥8 weeks Small but significant improvement in overall sleep (SMD -0.59), larger in people with insomnia. Mental alertness on rising and anxiety also improved; quality of life did not. No serious side effects reported. | 34559859 (opens PubMed)Source [4] |
| Anxiety scores (HAM-A) | Improved | Grade C | Meta-analysis · n = 254 · 2024 5 RCTs in people with anxiety and/or insomnia Form: Withania somnifera extracts · Dose: Varied across trials · Duration: Varied across trials Hamilton Anxiety scores fell by 5.96 points versus placebo; sleep onset, total sleep time, sleep quality and efficiency also improved. Heterogeneity was extreme (I² 98%). | 39083548 (opens PubMed)Source [3] |
| Morning cortisol | Improved | Grade C | RCT · n = 60 · 2019 Healthy adults with self-reported high stress Form: root-and-leaf extract (Shoden) · Dose: 240 mg/day · Duration: 60 days Greater reductions in morning cortisol and DHEA-S than placebo; Hamilton Anxiety score fell significantly, DASS-21 near-significantly. No adverse events. | 31517876 (opens PubMed)Source [5] |
| Muscle strength and size with resistance training | Improved | Grade C | RCT · n = 57 · 2015 Young men (18–50) new to resistance training Form: root extract · Dose: 300 mg twice daily (600 mg/day) · Duration: 8 weeks Greater gains than placebo in bench press (46.0 vs 26.4 kg) and leg extension (14.5 vs 9.8 kg), arm and chest size, and a larger drop in body fat percentage. | 26609282 (opens PubMed)Source [6] |
| Fatigue and vigor in older men | No effect | Grade C | Crossover RCT · n = 57 · 2019 Overweight men aged 40–70 with mild fatigue Form: root-and-leaf extract (Shoden, 21 mg withanolide glycosides/day) · Dose: 21 mg withanolide glycosides/day · Duration: 8 weeks per arm (16-week crossover) Fatigue, vigor and sexual well-being improved over time in both conditions with no significant difference from placebo. DHEA-S rose 18% and testosterone 14.7% more than with placebo. | 30854916 (opens PubMed)Source [7] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Root extract (e.g., KSM-66) | 5%[1] | No head-to-head human data comparing extracts in our sources.[1] | Mild stomach upset, loose stools, nausea and drowsiness are the common side effects reported across trials.[1] | Stress, anxiety, sleep (including insomnia), strength with resistance training |
| Root-and-leaf extract (Shoden) | 35%[1][7] | No head-to-head human data comparing extracts in our sources.[1] | No treatment-related adverse events in the 6-week sleep trial; no adverse events in the 60-day stress trial.[8][5] | Sleep quality, stress and cortisol, fatigue and hormones in older men |
| Root-and-leaf extract (Sensoril) | Varies[1] | No head-to-head human data in our sources.[1] | Included in the stress/anxiety trials summarized by ODS; no extract-specific tolerance data in our sources.[1] | Stress and anxiety (2 of 7 trials in the 2021 review cited by ODS used Sensoril or Shoden) |
| Whole root powder / granules | Varies[1] | No comparison data in our sources.[1] | No form-specific data in our sources.[1] | Stress and anxiety (one trial) |
Compound weight → elemental active
500 mg root extract (e.g., ksm-66) ≈ 25 mg elemental active
Studied doses
Doses studied in human trials ranged from 120 to 1,250 mg/day of standardized extract, for 6 to about 13 weeks. One trial gave 12 g/day of root granules, equivalent to 6 g of root powder. Extracts differ in plant part and withanolide content, so amounts are not interchangeable.[1][8]
Intake reference: No RDA, AI or UL exists for ashwagandha. ODS notes it is hard to define amounts because trials used different extracts and doses.[1] NIH ODS fact sheet (updated May 2, 2025).
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Thyroid hormone medicinesNIH fact sheetODS: ashwagandha might interact with thyroid hormone medicines; trials and case reports describe changes in TSH, T3 and T4, including three cases of thyrotoxicosis.[1]
- Antidiabetes medicinesNIH fact sheetListed by ODS as a possible interaction.[1]
- Blood pressure medicines (antihypertensives)NIH fact sheetListed by ODS as a possible interaction.[1]
- ImmunosuppressantsNIH fact sheetListed by ODS as a possible interaction.[1]
- SedativesNIH fact sheetListed by ODS as a possible interaction; drowsiness is a common side effect of ashwagandha.[1]
Who should be careful
- Pregnancy and breastfeeding
- Some experts advise against use in pregnancy. France's food-safety agency (ANSES, 2024) recommends against use while pregnant or breastfeeding, and Denmark banned ashwagandha in 2023; the American Herbal Pharmacopoeia disputes the evidence for harm in pregnancy.[1]
- Liver
- Rare liver injury has been reported, typically cholestatic with jaundice and itching 2–12 weeks after starting; in a 5-case series, liver tests normalized within 1–5 months after stopping. Some reported cases involved pre-existing liver disease, so people with liver conditions should talk to their clinician first.[10][1]
- Thyroid conditions
- An 8-week trial at 600 mg/day changed TSH, T3 and T4 compared with placebo, and thyrotoxicosis has been reported. Anyone with a thyroid condition or on thyroid medicine should speak with their clinician first.[11][1]
- Hormone-sensitive prostate cancer
- Ashwagandha may raise testosterone, and experts cited by ODS say it might not be safe for men with hormone-sensitive prostate cancer.[1][7]
- Long-term use
- Tolerated in trials of up to about 3 months; safety over many months or years is unknown.[1]
- Endocrine disorders
- ANSES recommends against use by people with endocrine disorders.[1]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
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Articles about Ashwagandha
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
What is the difference between KSM-66, Sensoril and Shoden?
They are branded extracts made differently. KSM-66 is a root extract (the sleep trial version had more than 5% withanolides); Shoden and Sensoril use root and leaf. Shoden delivered 21 mg withanolide glycosides in 60 mg. Trials of one extract do not automatically apply to another.[1]
Does ashwagandha help with stress?
Trials suggest it may lower perceived stress. A 2022 meta-analysis of 12 trials (n=1,002) found lower stress and anxiety scores than placebo, but certainty was low and results varied widely between trials, most of which were small and run in India.[2]
Does ashwagandha improve sleep?
Modestly. A 2021 meta-analysis of 5 trials (n=400) found a small improvement in overall sleep, larger in people with insomnia, at 600 mg/day or more, and after at least 8 weeks.[4]
Is ashwagandha safe for the liver?
Most people in trials tolerated it for up to 3 months, but rare cases of liver injury have been published. In a 5-case series, jaundice and itching appeared 2–12 weeks after starting and resolved within 1–5 months after stopping. Seek care for yellowing skin, dark urine or itching.[10][1]
Does ashwagandha raise testosterone?
Some small trials report increases: 14.7% more than placebo in older overweight men (n=57) and a larger rise in young men during resistance training. Another trial found no significant difference from placebo. Clinical relevance is unclear.[7][6][5]
Why did Denmark ban ashwagandha?
A 2020 Danish risk assessment raised concerns about possible effects on pregnancy and on thyroid and sex hormones, and Denmark banned it in 2023. The American Herbal Pharmacopoeia has said there is no evidence ashwagandha root causes abortions.[1]
Sources
- [1]Ashwagandha: Is it helpful for stress, anxiety, or sleep? Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025. fact-sheet
- [2]Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials.. Phytother Res, 2022. meta-analysis
- [3]Safety and efficacy of Withania somnifera for anxiety and insomnia: Systematic review and meta-analysis.. Hum Psychopharmacol, 2024. meta-analysis
- [4]Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis.. PLoS One, 2021. meta-analysis
- [5]An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study.. Medicine (Baltimore), 2019. RCT
- [6]Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial.. J Int Soc Sports Nutr, 2015. RCT
- [7]A Randomized, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha ( Withania somnifera) in Aging, Overweight Males.. Am J Mens Health, 2019. crossover-RCT
- [8]A randomized, double blind, placebo controlled study to evaluate the effects of ashwagandha (Withania somnifera) extract on sleep quality in healthy adults.. Sleep Med, 2020. RCT
- [9]Clinical evaluation of the pharmacological impact of ashwagandha root extract on sleep in healthy volunteers and insomnia patients: A double-blind, randomized, parallel-group, placebo-controlled study.. J Ethnopharmacol, 2021. RCT
- [10]Ashwagandha-induced liver injury: A case series from Iceland and the US Drug-Induced Liver Injury Network.. Liver Int, 2020. review
- [11]Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial.. J Altern Complement Med, 2018. RCT
- [12]Effects of ashwagandha (Withania somnifera) on mental health in adults: A systematic review and dose-response meta-analysis of randomized controlled trials.. Complement Ther Med, 2026. meta-analysis
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.
- Added cost-per-studied-dose method, labeled analysis derived from cited rows.