Ashwagandha benefits, side effects and dosage: what the evidence shows

Ashwagandha is a shrub root from Ayurveda, India's traditional medicine, and it has more human trial data than most herbs sold for stress. The best of it points one way: in adults who felt stressed, about 8 weeks of a root extract lowered stress scores and morning cortisol, the main stress hormone, more than a placebo did, and it nudged sleep in the right direction ³⁶⁷. The same trials show why it deserves more caution than a calming tea. Ashwagandha moves real hormones, including thyroid hormone and, in men, testosterone, and it is a recognized if rare cause of liver injury ⁹¹³². Whether it is worth it depends far more on your thyroid, your liver, your medicines and whether you might be pregnant than on which brand you pick.

What is ashwagandha?

Ashwagandha is the root of Withania somnifera, the most used medicine in Ayurveda ², and supplements use root, leaf or a mix of the two ¹; what it is and what it does in your body has its own page. This guide covers what it is good for and how strong the evidence is, how much studies use, when to take it and which form, and its side effects, interactions and blood tests.

The root holds more than 100 chemical constituents, including alkaloids, saponins and a family of steroid-like compounds called withanolides ². Withanolides are the compounds most suspected of doing the work, and of causing the side effects, which is why labels quote a withanolide percentage. That number is a standardization marker: it tells you how concentrated an extract is, so two products with the same milligrams can differ several-fold in what they deliver.

Ashwagandha is often called an adaptogen, a term for herbs said to help the body cope with stress. The more concrete idea, from Lopresti and colleagues' 2019 trial, is that it damps the HPA axis (the hypothalamus-pituitary-adrenal chain that releases cortisol under stress): in that trial morning cortisol and DHEA-S, an adrenal hormone, fell more on ashwagandha than on placebo ⁵. In the best-known stress trial, serum cortisol fell 27.9% over 60 days on ashwagandha against 7.9% on placebo ³.

On labels you will see branded extracts such as Shoden, used in two of Lopresti's trials ⁵¹³, plus generic root powder and root extract. LiverTox notes that capsules typically hold 150 to 600 mg of root extract, taken one to three times a day, so the total amount people swallow varies widely ².

What ashwagandha is good for: the evidence, graded

Each use below carries a grade. Strong means several good randomized trials or a meta-analysis agree; Moderate means several randomized trials, mostly positive but small or short; Limited means few or small trials, or mixed results; Early means lab, animal or a single pilot study; Not supported means good trials found no benefit. Our guide to how to read supplement evidence explains why a grade matters more than a headline. NCCIH's own summary is a useful anchor:

Research shows that some ashwagandha preparations may be effective for insomnia and stress. However, evidence is unclear about its effects on anxiety.National Center for Complementary and Integrative Health, Ashwagandha fact sheet, March 2023

What are the benefits of ashwagandha for stress?

Stress is where ashwagandha has its clearest record. In Chandrasekhar's 2012 trial, 64 adults with chronic stress took 300 mg of a concentrated root extract twice a day or a placebo for 60 days; scores on the Perceived Stress Scale (a 10-question stress questionnaire) fell 44.0% on ashwagandha against 5.5% on placebo ³. In Salve's 2019 trial of 60 stressed adults, both 250 mg and 600 mg a day lowered stress scores and serum cortisol over 8 weeks, with the larger amount doing more ⁴. Lopresti's 2019 trial used a different extract at 240 mg a day for 60 days and found a smaller effect: anxiety ratings improved, but the main depression-anxiety-stress questionnaire missed significance ⁵.

A 2022 meta-analysis pooled 12 trials with 1,002 people and found ashwagandha lowered stress and anxiety scores more than placebo, with the stress benefit clustered at 300 to 600 mg a day. The authors still rated the certainty of the evidence as low, because the trials were small, mostly run in India, often industry-funded, and their results varied a lot ⁶. That is why the grade is Moderate, not Strong.

Does ashwagandha help you sleep?

Modestly. Cheah's 2021 meta-analysis of 5 randomized trials and 400 adults found a small but significant improvement in overall sleep, plus better mental alertness on waking and lower anxiety, with no effect on quality of life ⁷. The benefit was larger in people diagnosed with insomnia, in trials that used 600 mg a day or more, and in trials of 8 weeks or longer. In Langade's 8-week trial, ashwagandha shortened the time to fall asleep and improved sleep efficiency (the share of time in bed spent asleep), more so in the insomnia group than in healthy sleepers ⁸.

Ashwagandha is not a treatment for insomnia, which a clinician diagnoses and treats. If you want to see whether your sleep schedule is the problem, our sleep calculator works out bedtimes around sleep cycles.

Benefits of ashwagandha for men: testosterone, strength and fertility

In Wankhede's 2015 trial, 57 young men new to weight training took 300 mg of root extract twice a day or a placebo for 8 weeks while lifting. Bench-press strength rose 46.0 kg on ashwagandha against 26.4 kg on placebo, and testosterone rose 96.2 ng/dL against 18.0 ng/dL ¹². In Lopresti's crossover trial of overweight men aged 40 to 70 with mild fatigue, salivary testosterone rose 14.7% and DHEA-S 18% more than on placebo over 8 weeks, but fatigue, vigor and sexual well-being did not differ ¹³. NCCIH sums it up as limited evidence that 2 to 4 months may raise testosterone and sperm quality ¹.

These are small, short trials. Low testosterone is diagnosed by a clinician from repeat morning blood tests and symptoms; see our low testosterone guide and the total testosterone marker page. Ashwagandha is never a swap for prescribed testosterone or fertility treatment, and because it may raise testosterone, NCCIH says men with hormone-sensitive prostate cancer should avoid it ¹.

Benefits of ashwagandha for women

Most stress and sleep trials enrolled both women and men, so the stress and sleep grades above apply to women too; in Chandrasekhar's trial, 23 of the 64 participants were women ³. In Lopresti's 240 mg trial, testosterone rose over time in men but not in women ⁵. For menopause symptoms and female fertility, NCCIH says there is not enough evidence to tell ¹. The issues that matter most for women are safety ones: NCCIH says to avoid ashwagandha in pregnancy and not to use it while breastfeeding, and thyroid conditions, which are common in women, are a reason to ask first ¹.

Ashwagandha and the thyroid

This is the effect that most often surprises people. In Sharma's 2018 pilot trial, 50 adults with subclinical hypothyroidism (a raised TSH of 4.5 to 10 with normal thyroid hormone) took 600 mg of root extract a day or a placebo. Over 8 weeks TSH fell and the thyroid hormones T3 and T4 rose significantly on ashwagandha ⁹. Ashwagandha is not a treatment for an underactive thyroid, which is diagnosed and treated by a clinician, and the same push can overshoot.

Case reports describe exactly that. A previously healthy 32-year-old woman developed thyrotoxicosis (an excess of thyroid hormone, with palpitations, shakiness and weight loss) after raising her ashwagandha dose, and it resolved once she stopped ¹⁰. A 73-year-old woman who had taken it for two years for an underactive thyroid arrived with a fast abnormal heart rhythm and a suppressed TSH, again resolving after stopping ¹¹. If you take levothyroxine, adding ashwagandha could add to your thyroid hormone, which is why NCCIH lists thyroid hormone medicines among its interactions ¹. Our hypothyroidism and hyperthyroidism guides cover what those diagnoses mean, and how to read your thyroid panel explains TSH, free T4 and free T3.

How much ashwagandha do studies use?

The table lists what trials gave, as a record of the research, not a dose for you. Extracts are not interchangeable: they differ in solvent, plant part and withanolide content, so a milligram figure only means something next to the product it came from.

There is no official upper limit for ashwagandha: no US agency has set one, and Denmark's 2020 risk assessment concluded it could not identify a safe lower intake at all ¹⁵. Liver injury has been reported across a wide range of amounts, from 154 mg taken on alternate days to 2,100 mg a day, which means no dose has been shown to be free of that risk ².

How LifeFrom's capsule compares: one capsule holds 380 mg of organic ashwagandha root powder plus 95 mg of root extract standardized to 1.5% withanolides, which works out to about 1.4 mg of withanolides from the extract. That is well below the 240 to 600 mg of concentrated extract used in the stress trials and far below the 21 mg of withanolide glycosides in Lopresti's men's trial, and the root powder is about a tenth of the 3 to 5 g traditional amount ⁵¹³¹⁵. The trial results are best read as an upper bound on what this amount might do.

When and how to take ashwagandha

How long does ashwagandha take to work? It is not felt in an hour the way caffeine is. Stress scores separated from placebo by 4 to 8 weeks in Salve's trial and by day 60 in Chandrasekhar's, and the sleep benefit was larger in trials lasting 8 weeks or more ³⁴⁷. NCCIH describes it as possibly safe for up to about 3 months, with too little information to judge longer use ¹. Cycling, meaning planned weeks on and off, is popular advice online but has not been tested in trials.

Time of day matters less than consistency. Because drowsiness is one of its reported side effects, some people prefer the evening ¹³. Taking it with food is the label's instruction and the simplest way to reduce stomach upset, which LiverTox attributes to direct irritation of the gut at larger doses ². On half-life, we found no reliable human study measuring how long ashwagandha's compounds stay in the blood, so any figure you see quoted online is a guess.

Forms: root extract or root powder

What are the side effects of ashwagandha?

In the trials, side effects were usually mild and about as common as on placebo; in Chandrasekhar's 60-day trial there were 6 mild events on ashwagandha and 5 on placebo ³. Outside trials, a short list of rarer problems needs prompt attention.

Is ashwagandha bad for your liver?

For most people it seems not to be, but it can be, and the cases are well documented. LiverTox rates ashwagandha “B”, a likely cause of clinically apparent liver injury, meaning injury that causes symptoms or jaundice and not only a blip in liver enzymes ². In clinical trials no liver enzyme rises were reported; the cases come from real-world use. They typically appeared 2 to 12 weeks after starting, with a cholestatic pattern (bile flow backing up), jaundice and itching, and most resolved within 1 to 4 months of stopping. The first case was reported in 2017 and the count has grown since ².

Two case series show the range. Björnsson and colleagues described 5 cases from Iceland and the US, aged 21 to 62, all of whom recovered within 1 to 5 months ². Philips and colleagues reported 8 people in India with liver injury from single-ingredient ashwagandha products that tested free of contaminants; 5 already had chronic liver disease, and 3 of those developed acute-on-chronic liver failure and died ¹⁴. LiverTox's conclusion is that ashwagandha should be avoided in people with cirrhosis or advanced chronic liver disease, and that anyone who has had a reaction should not take the same product again ². Our guide to liver enzymes explains how ALT, AST and bilirubin are read.

Why some countries restrict ashwagandha

Denmark's food authority, the Danish Veterinary and Food Administration, banned ashwagandha in food supplements after a 2020 risk assessment by the Technical University of Denmark found it could not set a safe intake level. The authority's public advice reads: “Do not eat Ashwagandha or supplements containing Ashwagandha because its root has negative effects on sex hormones and reproduction for both men and women” ¹⁵. In March 2024 the Netherlands' National Institute for Public Health and the Environment (RIVM) advised consumers against using ashwagandha preparations, citing reports from doctors of harm to the liver and to thyroid hormone and cortisol levels, plus its traditional use to induce abortion ¹⁶.

The decisions are contested. Patwardhan and colleagues, Ayurveda researchers writing in 2024, argued that the Danish report was not peer reviewed, leaned on leaf, stem and animal studies, and misread the source behind its abortion claim ¹⁵. In the US, ashwagandha is sold as a dietary supplement, which the FDA does not approve for safety or effectiveness before sale ¹. Both sides agree on the narrower point that matters here: there are real, if rare, liver and thyroid reports, and pregnancy is the one setting where nobody recommends it.

Who should avoid ashwagandha or ask first?

• Pregnancy: NCCIH says to avoid it, RIVM advises against it, and it has a traditional reputation for inducing abortion; there is no reassuring safety data ¹¹⁶.
• Breastfeeding: NCCIH says it should not be used ¹.
• Children: no safety studies in children; trials enrolled adults only.
• Thyroid disorders, under- or overactive: NCCIH does not recommend it, because it can raise thyroid hormone ¹⁹.
• Autoimmune conditions such as rheumatoid arthritis, lupus, multiple sclerosis or Hashimoto's thyroiditis: NCCIH does not recommend it ¹.
• Liver disease, especially cirrhosis: LiverTox says to avoid it; fatal cases have occurred in people with existing liver disease ²¹⁴.
• Hormone-sensitive prostate cancer: NCCIH says to avoid it, because it may raise testosterone ¹.
• Surgery: NCCIH says it is not recommended for people about to have surgery; tell your surgical team and anesthetist about it, and ask when to stop ¹.

Ashwagandha interactions

NCCIH lists six groups of medicines that ashwagandha might interact with ¹. Most of these are additive effects, so spacing the doses hours apart does not solve them. Never stop or change a prescribed medicine to make room for a supplement.

Supplements to pair or keep apart

Blood tests worth knowing about

No blood test measures ashwagandha itself, but several markers can move on it, and a few are the safety checks a clinician would think of. Ask your clinician whether any of these make sense for you, especially before and a couple of months after starting if you have a thyroid or liver condition.

A low TSH, a high free T4, or raised liver enzymes are results to take to your clinician, not to manage with supplement changes on your own. If you are holding a thyroid result, our TSH page explains what the numbers mean.

Conditions and goals it comes up around

People often look at ashwagandha because of a lab result or diagnosis. Hypothyroidism and hyperthyroidism are diagnosed and treated by a clinician; ashwagandha can push thyroid hormone up, which matters for both, and it is not a treatment for either. Low testosterone needs a proper workup, and our free testosterone calculator shows how total testosterone and SHBG combine. With fatty liver disease or any chronic liver condition, the LiverTox advice to avoid ashwagandha in advanced liver disease is the part to raise with your clinician ². A very high or very low cortisol result belongs with a clinician too; our Cushing's syndrome guide explains why. Ashwagandha is never a swap for a prescribed medicine.

Ashwagandha in the LifeFrom pouch

One capsule holds less concentrated extract than the stress and sleep trials used: 95 mg of extract plus 380 mg of root powder, against 240 to 600 mg of extract a day in those trials. Everything in a pouch is taken at the same time; in the Stress and Mood packs that puts ashwagandha with theanine and magnesium, and in the Mood pack also with rhodiola, combinations with no known interaction that have not been tested together in trials.

To see the full product list and how the packs are built, see the shop and its packs.

This guide is general education, not medical advice, and it cannot account for your health history. Supplements, ashwagandha included, are not approved by the FDA for safety or effectiveness. The clinician who knows your history, your thyroid and liver results and your medicines is the right person to decide whether ashwagandha fits; see our medical disclaimer.

Free in LifeFromAdd the lab results you already have, and LifeFrom reads each marker next to the others it moves with, in plain language, with the sources it used. Free, on the web or in the app.

Start on the web Download the app