Ashwagandha: What the Research Shows, How Much Is Used, and Who Should Avoid It

KEY TAKEAWAYS

•     Ashwagandha is a shrub used in Ayurveda for centuries, now one of the best selling supplements worldwide

•     The best evidence is for reducing stress and improving sleep, from multiple small, short trials

•     Most trials use 250 to 600 mg of root extract daily for 8 to 12 weeks

•     Rare cases of liver injury have been reported, and at least one European country has moved to restrict it

•     Avoid it in pregnancy, with thyroid or autoimmune conditions, liver disease, and before surgery

•     Tell your doctor you take it, since it can interact with thyroid, sedative, diabetes and blood pressure medicines

Few herbs have travelled from Indian kitchens and Ayurvedic texts to supplement shelves around the world as quickly as ashwagandha. In many Indian homes it has long been mixed into warm milk at bedtime. Today it is sold in capsules, gummies and drinks, often with bold promises attached. The research tells a more measured story.

Ashwagandha, known botanically as Withania somnifera and sometimes called Indian ginseng or winter cherry, is a small shrub whose root has been used in Ayurvedic medicine for more than 3,000 years. In Sanskrit, ashwagandha roughly translates as smell of the horse, a reference both to the root's odour and to the traditional belief that it gives the strength of a horse.

Today it is one of the most popular supplements in the world, usually marketed as an adaptogen, a substance claimed to help the body cope with stress. Some of the research is genuinely interesting. Some of the marketing is well ahead of it. This guide separates the two, and covers dosage, side effects, safety concerns and who should avoid it.

Ashwagandha in Ayurveda

In Ayurveda, ashwagandha is classed as a rasayana, a rejuvenating herb traditionally used to support strength, vitality, sleep and recovery from illness. It has been prescribed for fatigue, nervous exhaustion, poor sleep and general weakness, often for older adults and people recovering from long illness.

Traditional preparations differ from modern capsules. Common forms include churna, a powdered root often taken with warm milk and ghee, and fermented liquid preparations. Modern supplements are usually concentrated, standardised root extracts taken as capsules, which is also the form most clinical trials have used. Traditional use tells us how the herb has been used for centuries. It does not by itself establish safety or effectiveness at modern extract doses.

What an adaptogen is

Adaptogen is a term used for herbs said to help the body resist physical and mental stress and return to balance. It is not a recognised pharmacological category in mainstream medicine, and the word is used loosely in marketing. What matters more is what trials have actually measured, which for ashwagandha is mainly stress, anxiety, sleep, and a handful of physical outcomes.

What is in ashwagandha

The root contains compounds called withanolides, which are thought to be responsible for most of its effects, along with alkaloids and other constituents. Supplements are often standardised to a percentage of withanolides, which gives some consistency between batches. Leaf extracts have a different chemical profile, and most research has used root extract.

What the evidence shows

Claimed benefit	Strength of evidence	Summary
Stress and anxiety	Moderate	Several randomised trials show reduced self reported stress and cortisol versus placebo
Sleep	Moderate	Trials show improved sleep quality and sleep onset, particularly in people with insomnia
Muscle strength and exercise	Limited	Small trials with positive results, inconsistent overall
Testosterone and male fertility	Limited	Promising small studies, far from established
Cognitive function	Preliminary	Early studies only
Blood sugar	Limited	Modest effects in small studies
Thyroid	Evidence of an effect	Can raise thyroid hormone levels, which is a risk for many people

Stress and anxiety

This is the strongest area. Multiple randomised controlled trials have found reductions in self reported stress and anxiety and in cortisol levels compared with placebo, typically over eight weeks. The trials are mostly small, short, and often funded by supplement manufacturers, which limits confidence. The direction of results is consistent, however, which is more than can be said for many supplements.

Sleep

Several trials report improvements in sleep quality, time taken to fall asleep and total sleep time, especially in people with insomnia. The botanical name somnifera means sleep inducing, reflecting its traditional use. Effects appear modest and build over weeks rather than working like a sleeping tablet.

Physical performance and testosterone

Some small trials in men found improvements in muscle strength, recovery and testosterone levels with ashwagandha alongside resistance training. Others found smaller effects. This area is promising but not established, and it is heavily marketed relative to the evidence.

Dosage used in research

Trials typically use 250 mg to 600 mg per day of a standardised root extract, sometimes split into two doses, taken for 8 to 12 weeks. Higher doses are not proven to work better, and most studies have not continued beyond three months, so long term safety is not well established.

Traditional Ayurvedic preparations often use powdered whole root, commonly mixed with warm milk, at different amounts. Powder and extract are not interchangeable, since extracts are more concentrated. Do not convert doses yourself. Follow the product label and your doctor's advice.

What to expect over time

Ashwagandha is not a fast acting remedy. Unlike caffeine or L-theanine, most trials measure effects after several weeks of daily use.

Timeframe	What trials and users commonly report
First week	Often no noticeable change. Some people notice mild drowsiness or stomach upset
Weeks two to four	Some people report calmer mood and easier sleep
Weeks six to eight	The point at which most trials report measurable changes in stress and sleep
Beyond twelve weeks	Long term safety is not well established. Reassess with your doctor

Ashwagandha compared with other options for stress

Option	Speed of effect	Evidence for stress	Key caution
Ashwagandha	Weeks	Moderate	Rare liver injury, thyroid effects, avoid in pregnancy
L-theanine	30 to 60 minutes	Moderate for acute stress	Few side effects
Magnesium	Variable	Mainly if deficient	Digestive upset at high doses
Regular exercise	Days to weeks	Strong	Few risks for most people
Mindfulness practice	Weeks	Good	Uncommon distress with intensive practice
Talking therapy	Weeks to months	Strong for anxiety disorders	Access and cost

Supplements work best as one small part of a broader approach. Sleep, exercise, social connection and professional support where needed have much stronger evidence behind them than any herb.

The liver safety concern

There have been reports of liver injury associated with ashwagandha supplements, documented in medical literature and in drug induced liver injury databases. Cases are rare relative to how widely the supplement is used, and most improved after stopping, but some were serious. Regulators in several countries have reviewed the evidence, and Denmark moved to restrict ashwagandha following a national risk assessment.

Stop taking ashwagandha and contact a doctor promptly if you develop any of the following.

•     Yellowing of the skin or the whites of the eyes

•     Dark urine or pale stools

•     Unusual tiredness or weakness

•     Nausea, vomiting or loss of appetite

•     Pain in the upper right abdomen

•     Persistent itching

Common side effects

•     Stomach upset, nausea or diarrhoea, especially at higher doses or on an empty stomach

•     Drowsiness, which is why many people take it in the evening

•     Headache

•     Changes in thyroid hormone levels

Who should not take ashwagandha

Avoid ashwagandha, or speak to a doctor before using it, in any of these situations.

Situation	Reason
Pregnancy	Traditionally associated with pregnancy loss. Avoid
Breastfeeding	Insufficient safety data
Thyroid conditions or thyroid medication	It can raise thyroid hormone levels
Autoimmune conditions, such as lupus or rheumatoid arthritis	It may stimulate immune activity
Liver disease	Liver injury has been reported
Upcoming surgery	Possible interaction with anaesthesia and sedatives. Stop at least two weeks before
Hormone sensitive prostate cancer	It may raise testosterone
Children	Not well studied

Medicine interactions

Ashwagandha may interact with:

•     Sedatives and sleep medicines, increasing drowsiness

•     Thyroid medication, affecting hormone levels

•     Diabetes medicines, since it may lower blood sugar

•     Blood pressure medicines, since it may lower blood pressure

•     Immunosuppressants, since it may increase immune activity

Tell your doctor and pharmacist that you take ashwagandha. Supplements are frequently left off medication lists, and that is where interactions get missed.

Choosing a product sensibly

1.   Choose root extract, which is what most research used

2.   Look for standardisation to a stated withanolide percentage

3.   Check for third party testing for purity and contaminants, since heavy metal contamination has been found in some herbal products

4.   Start at the lower end of the studied range

5.   Take it with food to reduce stomach upset

6.   Use it as a time limited trial of 8 to 12 weeks, then reassess with your doctor

7.   Be wary of products making disease claims. No supplement should claim to cure anxiety, insomnia or any disease

Myths versus facts

Myth	Fact
Natural means safe	Rare cases of liver injury have been reported, and it interacts with several medicines
It works from the first dose	Most trials measure effects after several weeks
It boosts testosterone for everyone	Evidence is limited to small studies, mainly in men
More is better	Higher doses are not proven to work better and may increase side effects
Anyone can take it	It is not suitable in pregnancy, with thyroid or autoimmune conditions, or before surgery

Frequently asked questions

How long does ashwagandha take to work? Trials usually measure effects after four to twelve weeks. It is not an immediate remedy.

Should I take it in the morning or at night? Night suits many people because of drowsiness. Some split the dose. Either can work.

Can I take ashwagandha every day? Studies have used daily doses for up to about three months. Long term safety beyond that is not well established.

Is ashwagandha addictive? No dependence has been described.

Can women take ashwagandha? Yes, outside pregnancy and breastfeeding, and subject to the same precautions as anyone else.

Is ashwagandha powder with milk safe? It is a traditional preparation. The same precautions apply, and powder strength varies more than standardised extracts.

Does ashwagandha increase weight? There is no good evidence that it causes weight gain. Some small studies suggest it may reduce stress related eating.

DISCLAIMER

This article is for general information only and is not a substitute for professional medical advice, diagnosis or treatment. Please consult a qualified healthcare professional before making decisions about your health. Supplements can interact with medicines and are not suitable for everyone. This page may contain affiliate links.