What Is Ashwagandha? Benefits, Dose and Safety Explained
The short answer
Ashwagandha is the root of a small shrub, Withania somnifera, used for thousands of years in Ayurveda. Today it is mostly taken for stress and sleep, and small human studies suggest it may modestly lower stress, improve sleep and reduce cortisol over 6 to 12 weeks. It appears safe for most healthy adults in the short term, but it is not for pregnancy, thyroid or autoimmune conditions, and rare liver problems have been reported.
Ashwagandha has gone from a little-known Ayurvedic herb to one of the most searched supplements in the world. With that popularity has come a lot of overblown claims. This guide explains what ashwagandha actually is, what the research does and doesn't show, how people take it, and who should avoid it, so you can decide for yourself.
What is ashwagandha?
Ashwagandha (Withania somnifera) is an evergreen shrub that grows in India, parts of Africa and the Middle East. It is also called Indian ginseng or winter cherry, although it is not related to true ginseng. Most supplements use the root, sometimes with the leaves, ground into a powder or made into a concentrated extract (NIH Office of Dietary Supplements).
The name comes from Sanskrit and is usually translated as "smell of the horse", a nod to the root's strong, earthy smell and to the traditional belief that it gives the strength of a horse. In Ayurveda it is classed as a rasayana, a group of tonics taken daily to support overall vitality, and it has been used this way for thousands of years (NCCIH).
What does ashwagandha do?
Ashwagandha is usually described as an "adaptogen", a plant thought to help the body cope with stress. Its main active compounds are called withanolides, and supplements are often sold by how much of these they contain. Researchers believe ashwagandha may act on the body's stress-response system, which would explain why lower cortisol, the main stress hormone, shows up in several studies. The exact way it works is still not fully understood.
What the research shows
Ashwagandha has more human research than many herbal supplements, but most trials are small, short and use different extracts. Here is an honest summary:
| Area | What studies found | How strong |
|---|---|---|
| Stress and anxiety | A 2021 review of 7 trials (491 adults, 6 to 8 weeks) found lower stress, anxiety and cortisol than placebo, with larger effects at 500 to 600 mg a day (NIH ODS) | Moderate: several small trials, mostly in India |
| Sleep | A 2021 analysis of 5 trials (372 adults, 6 to 12 weeks) found a small improvement, strongest at 600 mg a day, after 8 weeks and in people with insomnia (NIH ODS) | Small but consistent |
| Testosterone in men | In 43 overweight men aged 40 to 70, testosterone rose 14.7% more than placebo over 8 weeks (American Journal of Men's Health) | Limited: few small trials |
| Strength with training | In 57 young men doing resistance training, 600 mg a day for 8 weeks gave greater strength and muscle gains than placebo (study summary) | Limited: one main trial |
| Memory, diabetes, menopause, fertility in women | Not enough evidence to say (NCCIH) | Unproven |
Two things are worth keeping in mind. First, many of these trials were funded by the companies that make the extract being tested. Second, results from one branded extract don't automatically apply to every ashwagandha product on the shelf.
How people take ashwagandha
Most studies used 250 to 600 mg a day of a root extract, usually standardised to around 5% withanolides, taken once or twice a day for 6 to 12 weeks. Powdered whole root is used in larger amounts, often mixed into warm milk, which is the traditional way.
A few practical points:
- Take it with food if it upsets your stomach.
- Morning or evening both work. Because it may make some people drowsy, many people take it in the evening.
- Give it time. Most studies measured effects after 6 to 8 weeks, not days.
- Take breaks. Its safety has only been studied for up to about three months at a time, so long, unbroken use is not well understood.
You will often see branded extracts such as KSM-66 (root only), Sensoril and Shoden (root and leaf). They are made differently and tested at different doses, so follow the amount on the label of the product you choose.
Side effects and who should avoid it
For most healthy adults, ashwagandha seems well tolerated for up to about three months. The most common side effects are mild: stomach upset, loose stools, nausea and drowsiness (NCCIH). There are also rare reports of liver injury, so stop taking it and see a doctor if you notice yellowing skin or eyes, dark urine or unusual tiredness.
Avoid ashwagandha, or speak to your doctor first, if you:
- are pregnant or breastfeeding
- have a thyroid condition or take thyroid tablets, as it may change thyroid hormone levels
- have an autoimmune condition or take immunosuppressants
- have hormone-sensitive prostate cancer, as it may raise testosterone
- take sedatives, sleeping tablets, anti-seizure treatment, or tablets for diabetes or blood pressure
- have surgery coming up
Regulators in some countries have gone further. Denmark banned ashwagandha in 2023, and France's food safety agency advised against it for pregnant and breastfeeding women and people with hormone disorders in 2024 (NIH ODS). Check the rules where you live.
How to choose a good ashwagandha
Look for a product that says which part of the plant it uses (root is the most studied), how much withanolide it contains, and the amount per daily serving. Prefer brands that publish independent lab tests for heavy metals and contaminants, since herbal products can carry them. Be wary of any brand promising dramatic results, because the research simply doesn't support that.
Ashwagandha and Shilajit: two Ayurvedic daily tonics
If you are interested in ashwagandha, you will probably come across Shilajit too, and many people take the two side by side. Both come from the same Ayurvedic tradition, and both have long been taken as daily rasayana tonics. But they are very different things.
Ashwagandha is a plant root, and its research centres on stress and sleep. Shilajit is a mineral-rich resin that forms over centuries in high mountain rock, rich in fulvic acid and trace minerals. Its human research is smaller and centres on different areas, including testosterone in middle-aged men, holding muscle strength during tiring exercise, and bone density in women after menopause. One is not a substitute for the other. We compare them side by side in Shilajit vs Ashwagandha, and our honest guide Does Shilajit Work? sets out what Shilajit's research does and doesn't show.
No studies have tested the two together. If you take medication for blood sugar, blood pressure or your thyroid, check with your doctor before combining them, since both may affect these.
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Frequently asked questions
What is ashwagandha good for?
The best evidence is for modestly lowering stress and improving sleep over 6 to 12 weeks. Smaller studies also suggest benefits for testosterone and strength training in men. Many other claimed benefits have not been shown in good human studies.
How long does ashwagandha take to work?
Most studies measured effects after 6 to 8 weeks of daily use, and sleep benefits were strongest after 8 weeks or more.
Is ashwagandha safe to take every day?
For most healthy adults it appears safe for up to about three months. Longer-term safety has not been studied well, and it is not suitable in pregnancy, breastfeeding, thyroid or autoimmune conditions.
Can I take ashwagandha and Shilajit together?
Many people do, but no studies have tested the combination. If you take medication for blood sugar, blood pressure or your thyroid, check with your doctor first.
This article is for general information only and is not a substitute for advice from your doctor. Statements about ashwagandha and Shilajit have not been evaluated by the FDA, and these products are not intended to diagnose, treat, cure or prevent any disease.
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Ready to try it? See our 30g Himalayan Shilajit resin or Shilajit drops, both lab tested batch by batch.