Ashwagandha: Benefits, Dosage, Side Effects & Safety

Short answer: Ashwagandha is an Ayurvedic herb that may modestly reduce stress and anxiety and slightly improve sleep, based on small trials lasting 6 to 12 weeks, usually with 250 to 600 mg a day of root extract. Evidence for strength, testosterone and other uses is weaker. It’s generally well tolerated short term, but rare cases of liver injury have been reported, and it isn’t suitable in pregnancy, with thyroid disease, or alongside sedatives. Use it for a few months at most and stop if you notice side effects.

Ashwagandha (Withania somnifera), sometimes called Indian ginseng or winter cherry, has been used in Ayurvedic medicine for centuries. Today it’s one of the most popular “adaptogen” supplements in the US, sold in capsules, gummies, powders and drinks for stress, sleep, energy and workouts. The research is more promising than for many herbs, but it’s still limited, and safety concerns have grown as use has increased. This guide covers what the evidence shows, how to take it and who should avoid it.

If stress is affecting your sleep, our comparisons of chamomile vs valerian and magnesium glycinate vs citrate may also help.

Ashwagandha at a glance

Plant part used: Mainly the root; some extracts include leaves
Best-studied uses: Stress, anxiety and sleep quality
Evidence: Limited to moderate; mostly small, short trials
Typical dose in trials: 250–600 mg a day of root extract
Time to work: Usually 4–8 weeks
Avoid if: Pregnant, breastfeeding, thyroid disease, liver disease, autoimmune disease, on sedatives

What is ashwagandha?

Ashwagandha is a small evergreen shrub in the nightshade family, native to India, the Middle East and parts of Africa. Its name comes from Sanskrit and refers to the root’s horse-like smell. In Ayurveda, it’s classed as a rasayana, a tonic used to promote vitality and resilience.

The root contains compounds called withanolides, which are thought to be responsible for most of its effects. Ashwagandha is often described as an adaptogen, meaning a herb that helps the body cope with stress. That’s a traditional concept rather than a medical one, but some trials have found that ashwagandha lowers cortisol, the main stress hormone.

What the research shows

Ashwagandha evidence by use
Use	Evidence	What trials found
Stress and anxiety	Moderate	Lower stress and anxiety scores and cortisol in several small trials
Sleep	Limited	Small improvement in sleep quality, mostly at 600 mg a day for 8 weeks or more
Strength and muscle	Limited	Some gains in strength and recovery with resistance training
Testosterone and fertility	Limited	Small increases in some men; quality of research is mixed
Memory and focus	Limited	Early, small studies only

Based on the NIH Office of Dietary Supplements ashwagandha fact sheet, NCCIH and the studies listed in the sources.

Key findings

Stress: according to the NIH Office of Dietary Supplements, most trials in adults with stress or anxiety found that ashwagandha reduced symptoms and cortisol more than placebo over 6 to 12 weeks. Most studies were small, and many were funded by supplement makers.
Sleep: a 2021 meta-analysis of 5 trials with about 400 people found a small but significant improvement in overall sleep, with larger effects in people with insomnia and at doses of 600 mg a day or more for at least 8 weeks (Cheah et al., 2021).
Exercise performance: a 2021 meta-analysis of 12 trials found that ashwagandha improved measures of strength, power and aerobic fitness more than placebo in healthy adults. The trials were small and mostly short, and several used the same branded extracts, so the authors called for larger, independent studies (Bonilla et al., 2021).
Long-term use: almost no studies have lasted longer than 3 months, so long-term safety and benefits are unknown.

A common pattern across ashwagandha research is that the people studied were generally healthy adults with mild to moderate stress, and results were measured with questionnaires over a few weeks. That means the benefits may be smaller in everyday use, especially with lower-dose products such as gummies. It also means the herb hasn’t been well tested in older adults, teenagers or people with chronic illnesses.

Ashwagandha isn’t a replacement for treatment if you have an anxiety disorder, depression or chronic insomnia. Talk to your doctor about proven options such as therapy and, where appropriate, medication.

Dosage and how to take it

Typical dose: 250 to 600 mg a day of a standardized root extract, often split into two doses. Raw root powder is weaker, and traditional doses are 3 to 6 grams a day.
Timing: take it with food to reduce stomach upset. Some people take it in the evening because it can make them drowsy.
How long: effects usually take 4 to 8 weeks. Because long-term safety isn’t known, many experts suggest limiting use to about 3 months and then taking a break.
Start low: begin at the lower end of the range and see how you feel.

Tip: keep a simple diary of your stress levels and sleep for a couple of weeks before and during use. It’s the easiest way to tell if a supplement is really helping or if you’d be better off saving your money.

Forms and extracts

Ashwagandha products vary widely, which partly explains mixed results. Common forms include:

Root extracts: standardized to a set percentage of withanolides, often 2.5 to 5 percent. Most clinical trials used branded root or root-and-leaf extracts, and results from one extract may not apply to another.
Root powder: the dried, ground root, traditionally mixed into warm milk. It’s cheaper but less concentrated.
Gummies and drinks: convenient, but often low-dose, with added sugar and unclear standardization.
Leaf products: some research suggests leaves contain different compounds; there’s less evidence for them, and some regulators have raised concerns about leaf extracts.

Side effects

In short-term studies, ashwagandha is usually well tolerated. The most common side effects are mild:

Upset stomach, nausea or diarrhea
Drowsiness or sluggishness
Headache

Stop taking it if side effects bother you or don’t go away.

Safety warnings and interactions

Who should be careful

Liver injury: rare but serious cases of liver injury have been reported in people taking ashwagandha, usually within 2 to 12 weeks of starting. Stop immediately and see a doctor if you develop yellow skin or eyes, dark urine, itching, unusual tiredness or stomach pain. Avoid it if you have liver disease.
Pregnancy and breastfeeding: avoid it. High doses may increase the risk of miscarriage, and safety in breastfeeding isn’t known. Denmark banned ashwagandha supplements in 2023, citing concerns including effects on pregnancy and hormones.
Thyroid conditions: ashwagandha may raise thyroid hormone levels. Avoid it if you have an overactive thyroid, and talk to your doctor if you take thyroid medicine.
Autoimmune diseases: it may stimulate the immune system, which could worsen conditions such as rheumatoid arthritis, lupus or multiple sclerosis.
Sedatives and alcohol: it may add to the effects of benzodiazepines, sleeping pills and alcohol.
Diabetes and blood pressure medicines: ashwagandha may lower blood sugar and blood pressure, so effects could add up.
Immunosuppressants: it may reduce the effect of drugs that suppress the immune system.
Hormone-sensitive prostate cancer: because it may raise testosterone, avoid it unless your doctor approves.
Surgery: stop at least 2 weeks before a planned operation.

How to choose a product

Choose a root extract with the dose and withanolide percentage clearly listed.
Prefer extracts that have been tested in trials, and match the trial dose.
Look for third-party testing, such as USP or NSF seals, which check for contaminants including heavy metals, a known issue with some Ayurvedic products.
Avoid proprietary blends that combine ashwagandha with many other herbs in undisclosed amounts.
Be wary of big claims: products promising to “balance hormones”, “melt belly fat” or “boost testosterone” go well beyond the evidence.

See our guide to reading a supplement label for more on testing seals and proprietary blends, and our herbal teas for sleep for gentler options.

Ashwagandha FAQ

How long does it take for ashwagandha to work?

Most trials measured effects after 4 to 8 weeks of daily use. Some people notice calmer moods sooner, but give it at least a month before deciding.

Should I take ashwagandha in the morning or at night?

Either works. Taking it in the evening may suit you if it makes you drowsy, and taking it with food helps prevent an upset stomach.

Can I take ashwagandha every day?

Most studies used daily doses for up to 3 months. Long-term safety isn’t known, so it’s sensible to take breaks and stop if you notice any side effects.

Does ashwagandha increase testosterone?

A few small studies in men found modest increases, but the research is limited. It’s not a substitute for medical treatment of low testosterone.

Can women take ashwagandha?

Yes, but not during pregnancy or breastfeeding. Women with thyroid or autoimmune conditions should talk to their doctor first.

Ashwagandha: Benefits, Dosage, Side Effects and Safety