Ashwagandha
botanical · also known as Withania somnifera, Indian ginseng, winter cherry, KSM-66, Sensoril
This is general information, not medical advice. Supplements can interact with medicines and health conditions. Always check with your doctor or pharmacist before starting or changing supplements.
What it is
Ashwagandha (Withania somnifera) is a shrub used for centuries in Ayurvedic medicine, whose root is traditionally used as an adaptogen, a substance believed to help the body handle physical and psychological stress. Modern supplements are typically standardised root extracts (commonly branded as KSM-66 or Sensoril) that concentrate withanolides, the plant's most-studied active compounds. Most human clinical research has concentrated over the last 10-15 years on stress and cortisol reduction, sleep, and exercise recovery, and this is now backed by several small-to-moderate randomised trials and a handful of meta-analyses, though individual trials generally remain small and short (weeks to a few months). Ashwagandha is usually well tolerated, but case reports have linked it to liver injury and to thyroid hormone changes in some users, and its safety in pregnancy has not been established.
Evidence-based benefits
- Grade A· Strong evidence[1]
Ashwagandha root extract supplementation reduces serum cortisol and perceived stress/anxiety scores compared with placebo across multiple randomised trials, with effects most consistent after 8 or more weeks of daily use.
A 2024 systematic review and meta-analysis of 9 randomised controlled trials (558 participants) found ashwagandha supplementation (125-600 mg/day for 30-90 days) significantly reduced Perceived Stress Scale scores (mean difference -4.72), Hamilton Anxiety Scale scores (mean difference -2.19), and serum cortisol (mean difference -2.58) compared with placebo. Effects were most consistent in trials lasting 8 or more weeks; four of the included studies reported mild-to-moderate adverse events.
- Grade B· Limited evidence[1]
Ashwagandha root extract improves anxiety and several sleep-quality measures compared with placebo, based on a small pool of randomised trials, with clearer effects in people who already have insomnia or anxiety.
A 2024 systematic review and meta-analysis pooling 5 randomised controlled trials (254 participants) found ashwagandha significantly reduced Hamilton Anxiety Scale scores (mean difference -5.96) and improved sleep onset latency, total sleep time, Pittsburgh Sleep Quality Index score, and sleep efficiency versus placebo, though no significant effect was found for wake-after-sleep-onset or time in bed. The authors noted high statistical heterogeneity across the pooled trials and called for larger studies to confirm the findings.
- Grade B· Limited evidence[1]
In young men undergoing resistance training, ashwagandha root extract (600 mg/day) increased gains in muscle strength, muscle size, and testosterone, and reduced body fat, compared with placebo, in a single randomised trial that has not been widely independently replicated.
An 8-week randomised, double-blind, placebo-controlled trial in 57 young men (18-50 years) undergoing resistance training found ashwagandha root extract (300 mg twice daily) produced significantly greater increases than placebo in bench-press one-rep max (+46.1 kg vs +26.4 kg, p=0.001), leg-extension one-rep max (+14.5 kg vs +9.8 kg, p=0.04), arm and chest muscle size (p=0.01 and p<0.001), serum testosterone (+96.2 ng/dL vs +18.0 ng/dL, p=0.004), and a greater reduction in body fat percentage (-3.5% vs -1.5%, p=0.03). This is a single trial from one research group; independent replication with different populations and formulations is limited.
Risks & contraindications
- Grade C· Preliminary evidence[1]
Rare case reports describe cholestatic or mixed-pattern liver injury associated with ashwagandha use, typically presenting with jaundice within weeks to a few months of starting the supplement and resolving after discontinuation.
A 2023 case report described a patient who developed jaundice 2 weeks after starting an ashwagandha herbal extract, with associated weight loss and diarrhoea; liver enzymes and bilirubin were elevated on admission, and all liver tests normalised within about 5 months of stopping ashwagandha (liver parameters had largely improved by 2 months post-discharge, with full normalisation by 5 months), without any specific treatment. This is one of several published cholestatic/mixed liver-injury case reports attributed to ashwagandha describing a similar pattern, though causality in any single case report can be confounded by other supplements or medications the patient was also taking.
- Grade C· Preliminary evidence[1]
Case reports describe ashwagandha use triggering biochemical or symptomatic thyrotoxicosis (suppressed TSH, hyperthyroid-type symptoms), particularly in people with pre-existing thyroid disease, with symptoms resolving after stopping the supplement.
A 2022 case report described a 73-year-old woman with underlying primary hypothyroidism (Hashimoto's thyroiditis) who had self- administered ashwagandha root extract for two years in place of levothyroxine, and who presented with palpitations, tremor, tachycardia, and a markedly suppressed TSH (<0.01 mcIU/mL) consistent with thyrotoxicosis. Her supraventricular tachycardia and symptoms resolved within two weeks of stopping ashwagandha, after which her thyroid function reverted toward her prior hypothyroid baseline. This and similar published cases suggest ashwagandha can meaningfully raise thyroid hormone activity in susceptible individuals, which is relevant for anyone taking thyroid medication or with known thyroid disease.
- Grade D· Traditional/anecdotal[1]
The safety of ashwagandha in pregnancy has not been established; traditional/ethnobotanical reports of abortifacient or teratogenic effects are inconsistent and contested, but authoritative reference sources still recommend avoiding ashwagandha during pregnancy pending adequate human safety data.
A 2026 systematic and ethnobotanical review found that historical claims of ashwagandha's abortifacient/teratogenic potential rest on inconsistently sourced ethnobotanical reports affected by citation distortion and a lack of primary-source validation, and that animal reproductive-toxicology studies have not shown significant reproductive toxicity at human-relevant doses. The same review notes, however, that robust human pregnancy-safety data are still lacking, and mainstream reference sources (e.g., the NIH Office of Dietary Supplements) state there is not enough reliable evidence to consider ashwagandha safe during pregnancy. Given this uncertainty on both sides, avoidance during pregnancy remains the precautionary standard rather than a confirmed- harm finding.
Dosage & how to take it
- Standardised root extract: 300–600 mg/day, any time of day, with or without food. Trials showing stress, sleep, or strength benefits have generally used 300-600 mg/day of standardised root extract, either once daily or split into two doses (morning and evening, or twice daily with meals); trials focused on sleep have sometimes dosed in the evening. Most trials have run 6-12 weeks; there is no established hard safety limit on continuous use, but human trial data covering longer continuous use are limited, and case reports of liver and thyroid effects (see risk claims above) argue for periodic reassessment rather than indefinite, unmonitored use, especially for anyone with liver or thyroid disease.
Interactions
Ashwagandha is thought to affect serotonin signalling, and a published case report described a woman on long-term escitalopram (an SSRI) who developed serotonin syndrome, a potentially serious reaction with symptoms like muscle jerking, fever, and a fast heart rate, after taking a high dose of ashwagandha (a 600 mg capsule plus ashwagandha tea) shortly before she was hospitalised. This is a single case report rather than a controlled study, so it doesn't establish how often this happens or at what dose, but it's enough to warrant caution: if you take an SSRI like sertraline, talk to your prescriber before adding ashwagandha, watch for symptoms like agitation, sweating, tremor, or a racing heart if you do combine them, and stop and seek care if they appear.
Ashwagandha has been linked, in published case reports, to raising thyroid hormone activity, and in rare cases has even caused thyrotoxicosis (biochemical or symptomatic overactive thyroid) on its own. Combining it with a thyroid hormone medication like levothyroxine could theoretically push thyroid hormone levels higher than intended, on top of your prescribed dose. One case report described a woman with hypothyroidism who self-substituted ashwagandha for her levothyroxine for two years and developed thyrotoxicosis with a rapid heart rhythm, which resolved after stopping the ashwagandha; that case involved ashwagandha replacing medication rather than being added to it, so it's not direct proof of an additive effect when taken alongside levothyroxine as prescribed, but it shows ashwagandha alone can meaningfully move thyroid hormone levels. If you take thyroid medication, tell your prescriber before starting ashwagandha and ask about periodic thyroid function checks.
Our medication coverage is not exhaustive. Absence of a warning here is not evidence of safety. Always confirm with your pharmacist.
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