Ashwagandha: Why you need to take?

The short answer

You do not need ashwagandha — nobody is deficient in it, and it is not a vitamin. But there is a reasonable case for trying it if stress is wearing you down and has started to affect your sleep. Of all the herbs sold for stress, it has the most placebo-controlled trials behind it, and they point the same way: at 300 to 600 mg of root extract a day, people report feeling less stressed after about eight weeks, their cortisol falls, and they sleep a little better.

That is the case for it. The case for caution is just as real: the trials are small, short and mostly funded by extract makers; it has been linked to rare liver injury; it can change thyroid hormone levels; and Denmark has taken it off the shelves. Used well, it is a short, deliberate experiment — not something to take forever.

What is ashwagandha?

Ashwagandha (Withania somnifera) is a small shrub in the nightshade family whose root has been used in Ayurvedic medicine for thousands of years. Its Sanskrit name means roughly “smell of the horse”, after the root’s odour and the strength it was said to give. You will also see it called Indian ginseng or winter cherry.

It is sold as an adaptogen — a plant said to help the body cope with stress. That is a traditional and marketing term rather than a medical one, but it explains why ashwagandha turns up in everything from sleep gummies to “cortisol” blends and testosterone boosters. The compounds thought to do the work are called withanolides.

Why people take it: the evidence, claim by claim

We grade each claim separately, because a herb can have decent evidence for one thing and none for another. Here is how ashwagandha stands.

1. For stress and anxiety — the main reason

A 2022 meta-analysis pooled 12 randomised trials and 1,002 adults and found ashwagandha lowered stress and anxiety scores more than placebo, with 300 to 600 mg a day doing best for stress. In one of the best-known trials, 64 chronically stressed adults took 300 mg of root extract twice a day for 60 days: their stress scores fell by 44 per cent, and their cortisol by 27.9 per cent against 7.9 per cent on placebo.

Encouraging — but the review’s own authors rated the certainty of the evidence as low. Most trials ran for eight weeks, were small, and were paid for by the company whose extract was being tested. It is not a treatment for an anxiety disorder, and if anxiety is stopping you living normally, that is a conversation for your GP.

2. For sleep

A 2021 review of five trials and 400 people found a small but real improvement in sleep. It was bigger in people with insomnia, at doses of 600 mg a day or more, and after at least eight weeks. People also felt more alert on waking. It will not knock you out like a sleeping pill — the effect is gentler than that, and it takes weeks.

3. For training, testosterone and memory

These are the claims that sell supplements to men and students, and they rest on thinner ground. A 2021 analysis found gains in strength and fitness in people who were training, but the strength result came from just five small trials. An eight-week trial in 43 men aged 40 to 70 found testosterone rose 14.7 per cent more than on placebo — yet the men did not feel more energetic. A few small trials report better memory scores. All are worth watching; none is established.

4. For weight loss — no

Ashwagandha often appears in “cortisol belly” products on the idea that less stress means less stress eating. There is no good evidence that it causes meaningful weight loss.

Is ashwagandha for you?

How to take it properly

The dose

Almost every trial used 250 to 600 mg a day of a standardised root extract, either once a day or split into two doses. For stress, 300 to 600 mg did best; for sleep, the benefit was clearer at 600 mg. Many people take it in the evening because it can make you drowsy, but no trial has shown that timing matters.

Choose the right form

This matters more than the brand. A label that just says “ashwagandha 500 mg” may be plain root powder, which is far weaker than the extracts that were actually tested. Look for a named extract or a withanolide percentage on the panel.

Form on the label	What it is	What to know
KSM-66	Root-only extract, about 5% withanolides	Used in many of the stress, sleep and strength trials; typical dose 300 mg once or twice a day
Sensoril	Root and leaf extract, at least 10% withanolides	Studied at lower doses, 125–500 mg a day
Shoden	Root and leaf extract, about 35% withanolide glycosides	Used in the testosterone trial at 600 mg a day
Root powder	Dried, ground root, not concentrated	Traditional use runs to several grams a day; milligram doses of powder were not what the trials tested
Gummies and blends	Ashwagandha mixed with other ingredients	Often a hidden amount in a proprietary blend, plus sugar, melatonin or caffeine

Not sure which product to buy? We compared six US labels on extract, dose and cost a day in which ashwagandha brand is best to buy.

Run it as an eight-week experiment

What to expect along the way is covered week by week in what happens if you take ashwagandha daily.

1. 1
   Before you start

   Pick a named root extract (such as KSM-66) at 300–600 mg a day. Check it is not already in another product you take.

2. 2
   Weeks 1–2

   Watch for loose stools, nausea or daytime drowsiness. Taking it in the evening, with food, helps some people.

3. 3
   Weeks 3–6

   Any effect on stress or sleep builds slowly. Note how you sleep and feel, so you are not guessing later.

4. 4
   Week 8

   Decide. The trials measured their results here. No change by now? It is unlikely to come — stop.

5. 5
   By month 3

   Take a break. Safety data run to about three months, so do not let it become open-ended.

6. Stop at once and see a doctor if you notice yellow skin or eyes, dark urine, pale stools, itching or pain under your right ribs — possible signs of liver injury.

The risks you should know about

Most people in trials had no problems beyond mild stomach upset, loose stools or drowsiness. But a few risks are worth taking seriously, because they are not printed on the tub.

• Liver injury. The NIH’s LiverTox database rates ashwagandha a probable cause of liver injury. It is rare, typically appears 2 to 12 weeks after starting, and usually clears within months of stopping — but severe cases have occurred, mostly in people with existing liver disease.
• Thyroid. It can raise thyroid hormone levels. Avoid it with an overactive thyroid, and check with your doctor if you take thyroid medicine.
• Pregnancy and breastfeeding. Do not take it. It has traditionally been linked to miscarriage and there are no safety data.
• Medicines. It may add to the effect of sedatives and sleeping tablets, lower blood sugar and blood pressure, and stimulate the immune system. Ask a pharmacist if you take any regular medicine.
• Surgery. Stop two weeks before an operation.

Why Denmark banned it — and where the UK stands

In 2023, Denmark banned ashwagandha from food supplements after its national food institute concluded that a safe level of intake could not be established, citing possible effects on hormones and reproduction. Researchers and the industry have criticised the assessment behind the ban. In the UK, the Food Standards Agency has asked the Committee on Toxicity to review its safety; the committee has noted possible effects on the thyroid, blood sugar and reproduction as well as the liver case reports, and no safe level has yet been set. In the US it is sold as a dietary supplement, which means nobody checks it for safety or effectiveness before it goes on sale.

None of this means a short course is dangerous for a healthy adult. It does mean ashwagandha is not the harmless “natural” herb the packaging suggests, and that taking it for years is a step into the unknown.

What to try before — or alongside — ashwagandha

A supplement works best on top of the basics, not instead of them. The things with the strongest evidence for stress and sleep cost nothing: a regular sleep and wake time, less caffeine after midday, daylight and exercise, and talking therapies such as CBT, which the NHS offers free through its talking therapies service. If you want something gentler to try first, L-theanine has a cleaner safety record, though its evidence is narrower.

The bottom line

If stress is getting to you and you are a healthy adult on no regular medicines, ashwagandha is one of the few herbs with a reasonable body of trials behind it. Choose a named root extract, take 300 to 600 mg a day, give it eight weeks, and stop if nothing changes — or at three months regardless. If you are pregnant, have liver or thyroid problems, or take regular medicines, it is not for you without a doctor’s say-so. And if stress or poor sleep has gone on for months, the most useful next step is your GP, not a supplement.

For the full evidence grades, dose ranges and every reference, see our ashwagandha ingredient page.