Ashwagandha: Evidence, Benefits, Dosage and Safety

Ashwagandha: What Human Research Really Shows About Benefits, Dosage and Safety

Ashwagandha (Withania somnifera) has moved from traditional Ayurvedic medicine into mainstream supplement use. Today, people take or consider taking it for stress, sleep, anxiety, energy, exercise performance, testosterone and other health goals.

The difficult part is not finding claims about Ashwagandha. There are thousands of them.

The difficult part is deciding which claims are supported by human research, which are still uncertain, and whether a study of one Ashwagandha extract can reasonably be applied to the product on a store shelf.

Current evidence suggests that some Ashwagandha preparations may help with stress and insomnia. Research on anxiety has produced promising findings but remains uncertain, while evidence for many other popular uses is insufficient. Safety also deserves careful attention because short-term studies do not establish long-term safety, and rare cases of clinically apparent liver injury have been reported.

The most useful way to approach Ashwagandha is therefore not as a universal wellness herb, but as a botanical supplement with specific evidence, important uncertainties and real safety considerations.

What Is Ashwagandha?

Ashwagandha is an evergreen shrub whose scientific name is Withania somnifera. It has a long history of use in Ayurvedic medicine.

Traditional Ayurvedic use and modern clinical research answer different questions.

Ayurvedic descriptions may discuss concepts such as nourishment, strength, vitality and Rasayana use. Modern clinical research instead asks whether a particular preparation changes a measurable outcome in human participants.

Those two perspectives can be discussed respectfully without treating traditional use as proof of modern clinical effectiveness.

Ashwagandha supplements may contain:

• Root

• Leaf

• Root-and-leaf preparations

• Powder

• Concentrated extracts

• Standardized extracts

• Combinations with other ingredients

This difference is important because “Ashwagandha” is not necessarily one chemically or clinically identical product. NCCIH notes that studies have used a variety of preparations, and many clinical trials have been relatively small.

Why One Ashwagandha Study Cannot Automatically Represent Every Product

Suppose a clinical trial finds that a particular standardized root extract improved a stress score after eight weeks.

That tells us something about that preparation, dose, study population and treatment period.

It does not automatically tell us that:

• raw root powder will have the same effect,

• a leaf extract will have the same effect,

• a lower concentration will work similarly,

• a different standardized extract will produce the same result,

• a multi-herb product will behave the same way, or

• taking more will produce a greater benefit.

This is one of the most important points missing from many supplement discussions.

The name of the plant identifies the botanical ingredient, but it does not completely describe the preparation being tested.

What Does Human Research Actually Suggest?

The evidence is not equally strong across all proposed uses.

NCCIH currently states that some Ashwagandha preparations may be useful for stress and insomnia, while evidence for anxiety remains unclear. It also says there is limited evidence that use over approximately two to four months may increase testosterone and sperm quality, while evidence is insufficient for conditions including athletic performance, cognitive function, diabetes, menopause and female infertility.

A 2024 systematic review and meta-analysis included nine randomized controlled trials involving 558 participants and reported improvements in perceived stress, an anxiety measure and cortisol compared with placebo. However, the authors also highlighted the need for more information about longer-term safety.

A newer 2026 systematic review included 22 studies and reported promising findings for stress, anxiety and depression. Importantly, the authors also identified heterogeneity between studies and said better-quality research is needed before the findings can be translated into firm clinical recommendations.

So the most responsible interpretation is:

There is meaningful human research suggesting that some Ashwagandha preparations may help certain stress- and sleep-related outcomes, but the evidence does not establish Ashwagandha as a universal treatment for psychological or physical health conditions.

Stress: One of the More Relevant Areas of Research

Stress is one of the better-studied reasons people use Ashwagandha.

Clinical trials have examined outcomes including perceived stress and cortisol. Several studies have reported improvements compared with placebo, and systematic reviews have generally found a signal suggesting possible benefit.

But there is an important distinction between a statistically measurable improvement in a study and a guaranteed meaningful improvement for an individual.

Studies differ in:

• Type of extract

• Amount used

• Duration

• Participant characteristics

• Stress measurement tools

• Study quality

Therefore, it is reasonable to say that Ashwagandha may help some adults with perceived stress, but it is not reasonable to promise that it will reduce stress for everyone.

It should also not replace approaches that address the causes and circumstances of chronic stress.

Sleep: Promising, But Not a Universal Insomnia Treatment

Sleep is another area where evidence is reasonably encouraging.

NCCIH states that some Ashwagandha preparations may be useful for insomnia.

However, poor sleep is not one single condition.

Difficulty sleeping may be associated with:

• Irregular sleep schedules

• Stress or anxiety

• Chronic pain

• Medication effects

• Caffeine or alcohol use

• Depression

• Sleep apnea

• Other medical conditions

If someone has persistent insomnia, loud snoring with breathing pauses, severe daytime sleepiness or another concerning pattern, taking a supplement without investigating the underlying problem may delay appropriate care.

Ashwagandha research therefore should not be interpreted as evidence that every type of insomnia is caused by stress or will respond to the herb.

Anxiety: Why “Promising” Does Not Mean “Proven Treatment”

Anxiety is frequently used in Ashwagandha marketing, but the evidence requires careful wording.

The 2024 meta-analysis found improvements in anxiety-related measurements, while NCCIH currently describes the evidence on anxiety as unclear.

A further 2026 systematic review reported promising findings across stress, anxiety and depression outcomes but emphasized study heterogeneity and the need for higher-quality research.

This means the evidence is worth studying, but it should not be converted into a claim that Ashwagandha treats an anxiety disorder.

Persistent anxiety, panic attacks, depression, severe distress or symptoms that interfere with daily functioning deserve appropriate professional assessment.

What About Cortisol?

Cortisol is often used in Ashwagandha marketing because some trials have reported reductions in cortisol.

But “lower cortisol” should not automatically be translated into “better health.”

Cortisol is a normal hormone involved in metabolism, immune regulation and the body's response to stress. Its levels naturally vary with factors such as time of day, illness, sleep and physical stress.

Therefore, a reduction in cortisol in a clinical trial is a research outcome, not proof that someone needs to lower their cortisol.

This is an important example of why biological mechanisms should not be confused with health outcomes.

Testosterone and Male Fertility: Interesting but Limited Evidence

Some research has investigated Ashwagandha in men, including testosterone levels and sperm-related measures.

NCCIH describes the evidence as limited and notes that studies lasting approximately two to four months have suggested possible increases in testosterone and sperm quality.

That is different from proving that Ashwagandha treats male infertility.

Male infertility can involve:

• Sperm production problems

• Hormonal disorders

• Varicocele

• Genetic factors

• Medication effects

• Infections

• Lifestyle factors

• Other reproductive conditions

A supplement should not delay evaluation when fertility is a concern.

Similarly, a change in a laboratory measurement such as testosterone does not automatically mean that a person will experience a meaningful improvement in symptoms, fertility or sexual health.

Exercise, Memory, Diabetes and Menopause

Ashwagandha is also marketed for exercise performance, muscle growth, cognition, blood sugar control and menopause.

These claims should not be given the same weight as the better-studied stress and sleep questions.

NCCIH currently states that there is insufficient evidence to determine whether Ashwagandha is helpful for athletic performance, cognitive function, diabetes, menopause or female infertility.

“Insufficient evidence” does not mean that an effect has been disproved.

It means the available research is not strong or consistent enough to make a reliable clinical conclusion.

That distinction is important because supplement marketing often turns an interesting preliminary finding into a confident health promise.

Is There a Universal Ashwagandha Dose?

There is no single dose that can safely be treated as the universal Ashwagandha dose for every person and every product.

Clinical studies use particular preparations, concentrations, dosing schedules and treatment periods.

For example, a 2026 randomized safety study evaluated a particular Ashwagandha root extract at 600 mg per day for eight weeks in 1,002 adults with reported stress and anxiety. The study found no serious adverse events and no significant differences in several laboratory safety measures between the extract and placebo groups.

That result should not be interpreted as:

“600 mg is the correct dose for everyone.”

It was a study of a specific extract under specific research conditions.

A product label should therefore be considered in context rather than converted into a generic internet dosing rule.

Check the Product Before Comparing Doses

Look for:

• Plant part used

• Amount of extract

• Serving size

• Standardization information, if provided

• Other active ingredients

• Manufacturer information

• Quality-testing information where available

A few grams of ordinary root powder cannot automatically be considered equivalent to a few hundred milligrams of a concentrated extract.

How Long Should Someone Take It?

There is also no universally established duration for all Ashwagandha products and all health goals.

Many trials last several weeks or a few months. That does not establish that continuous use for many months or years is safe.

NCCIH currently says short-term use, up to about three months, may be safe for some people but that there is not enough information to draw conclusions about long-term safety.

This is one reason “take it indefinitely because it is natural” is not a medically responsible approach.

Ashwagandha Safety: What Matters Before Starting

Ashwagandha can cause side effects. NCCIH lists possible drowsiness, stomach upset, diarrhea and vomiting.

More importantly, rare cases of clinically apparent liver injury have been reported.

LiverTox describes cases in which liver injury typically appeared within approximately two to twelve weeks after starting Ashwagandha, often involving jaundice and itching. Severe outcomes have also been reported, particularly among people with pre-existing liver disease.

This does not mean liver injury is common.

It means that a rare but potentially serious adverse effect deserves attention because people may otherwise assume that a traditional herb cannot harm the liver.

Warning Signs That Need Medical Attention

If someone taking Ashwagandha develops symptoms such as:

• Yellow skin or yellowing of the whites of the eyes

• Dark urine

• Significant itching

• Persistent nausea or vomiting

• Unusual or severe fatigue

• Significant abdominal discomfort

they should stop treating the symptoms as an ordinary supplement reaction and seek medical evaluation.

Suspected supplement-related liver injury should not be managed by simply switching brands or restarting the same product.

Who Should Avoid Ashwagandha or Get Professional Advice?

NCCIH advises avoiding Ashwagandha during pregnancy and not using it while breastfeeding. It also does not recommend it for people with autoimmune or thyroid disorders or for people preparing for surgery.

Extra caution is appropriate for people who:

• Have liver disease

• Have advanced chronic liver disease or cirrhosis

• Have a thyroid disorder

• Have an autoimmune condition

• Have hormone-sensitive prostate cancer

• Are pregnant or breastfeeding

• Are preparing for surgery

• Take several prescription medicines

• Have unexplained symptoms that they are trying to self-treat

People with medical conditions should not assume that a supplement can be evaluated independently of their existing treatment.

Possible Medication Interactions

NCCIH identifies possible interactions with several categories of medicines, including:

• Diabetes medicines

• Blood-pressure medicines

• Sedatives

• Anti-seizure medicines

• Immunosuppressants

• Thyroid hormone medicines

This does not mean that every person taking one of these medicines will experience an interaction.

It means the combination deserves review before use.

If you take prescription medication regularly, a pharmacist or doctor can check the specific product and medication combination rather than relying on a general internet list.

Why Product Quality Matters

Clinical research is performed on defined preparations. Commercial supplements may differ in their ingredients and manufacturing.

Potential differences include:

• Root versus leaf

• Extraction method

• Concentration

• Withanolide content

• Additional herbs

• Excipients and other ingredients

• Manufacturing quality

This matters for both effectiveness and safety.

LiverTox also notes an important complication with herbal products: commercial preparations may contain multiple ingredients, and in some cases contamination or mislabeling can make it difficult to determine exactly what caused an adverse event.

A sensible approach is to choose products with transparent ingredient labeling and avoid products that make an extraordinary number of disease-treatment claims.

Traditional Ayurvedic Use Versus Modern Evidence

Ashwagandha has a long history within Ayurveda, where it has traditionally been associated with concepts of nourishment, strength and rejuvenation.

Those traditional concepts are important for understanding the herb's historical use.

Modern clinical research asks different questions.

For example:

Traditional use: Ashwagandha has been used traditionally as a strengthening or rejuvenating herb.

Possible biological mechanisms: Laboratory research has identified biologically active compounds such as withanolides.

Human evidence: Clinical trials have tested particular preparations for outcomes such as stress, sleep and other measures.

Clinical conclusion: A laboratory mechanism or traditional use does not prove that a supplement treats a particular disease.

This distinction allows traditional knowledge to be acknowledged without presenting it as equivalent to clinical evidence.

A Practical Way to Decide Whether Ashwagandha Is Appropriate

Before starting an Ashwagandha supplement, ask five questions.

1. What am I actually trying to improve?

“General health” is too broad to evaluate.

A specific goal such as occasional stress or sleep difficulty is easier to assess than a goal such as “balance hormones” or “detox the body.”

2. Could the symptom have another cause?

Persistent fatigue, insomnia, anxiety, changes in weight or reproductive problems can have many causes.

If an underlying medical condition is possible, investigation may be more useful than self-treatment.

3. Does the evidence apply to my situation?

Consider whether the research involved:

• A similar age group

• A similar health status

• The same type of preparation

• A comparable dose

• A comparable duration

4. Do I have a reason to avoid it?

Pregnancy, breastfeeding, thyroid or autoimmune disease, liver disease, upcoming surgery and certain medicines are important considerations.

5. Do I understand when to stop?

Anyone using a supplement should know what adverse effects require medical attention.

For Ashwagandha, new jaundice, dark urine, marked itching or significant unexplained illness should not be ignored because rare liver injury has been reported.

When Ashwagandha Is Not the Right First Step

A supplement may be the wrong starting point when the symptom itself needs investigation.

Medical evaluation is more appropriate for situations such as:

• Persistent or severe anxiety

• Depression or suicidal thoughts

• Long-lasting or unexplained insomnia

• Unexplained severe fatigue

• Unexplained major weight changes

• Symptoms suggesting thyroid disease

• Signs of liver disease

• Persistent digestive symptoms

• Fertility problems requiring evaluation

The purpose of this distinction is not to discourage all supplement use.

It is to prevent a supplement from becoming a substitute for identifying an underlying problem.

What the Evidence Can Reasonably Support

Based on current evidence:

Stress: Some Ashwagandha preparations may improve perceived stress in some adults.

Sleep: Some preparations may improve certain sleep outcomes, particularly in people experiencing sleep difficulties.

Anxiety: Research is promising but evidence remains uncertain enough that Ashwagandha should not be presented as an established treatment for anxiety disorders.

Testosterone and sperm quality: Limited evidence suggests possible effects in particular male populations, but this does not establish treatment for infertility.

Athletic performance and cognition: Evidence remains insufficient for firm conclusions.

Diabetes, menopause and female infertility: Current evidence is insufficient to recommend Ashwagandha as treatment.

Long-term safety: Not established.

Liver safety: Rare clinically apparent liver injury has been documented.

These distinctions are more useful than simply labeling Ashwagandha as either “effective” or “ineffective.”

Key Takeaways

• Ashwagandha (Withania somnifera) has a long history in Ayurvedic medicine, but traditional use is not the same as clinical proof.

• Current human evidence is most relevant to stress and some sleep outcomes.

• Evidence concerning anxiety is promising in some studies but remains uncertain.

• Limited research has examined testosterone and sperm quality in particular male populations.

• Evidence is currently insufficient for many other popular claims, including cognition, athletic performance, diabetes, menopause and female infertility.

• A study dose for one extract should not automatically be treated as the correct dose for every Ashwagandha product.

• Short-term research does not establish long-term safety.

• Rare cases of clinically apparent liver injury have been reported.

• Pregnancy and breastfeeding are situations in which Ashwagandha should be avoided.

• People with thyroid or autoimmune disorders, liver disease, upcoming surgery or relevant medication use should obtain professional advice before taking it.

• The most responsible question is not “Does Ashwagandha have benefits?” but “Does the evidence for this particular preparation and purpose apply to me, and is using it appropriate given my health and medicines?”

Medical Disclaimer

This article is provided for general educational purposes and is not a substitute for individualized medical advice, diagnosis or treatment. Ashwagandha is a biologically active herbal supplement and may cause side effects or interact with medicines and medical conditions. Do not use this information to delay medical evaluation or replace treatment prescribed by a qualified healthcare professional. Seek professional advice before using Ashwagandha if you are pregnant or breastfeeding, have liver, thyroid or autoimmune disease, are preparing for surgery, have hormone-sensitive prostate cancer, or take prescription medicines.

Related Articles: 

Ashwagandha is one of the better-known plants traditionally used in Ayurveda. To explore other botanicals used in traditional Ayurvedic practice, see our guide to Ayurvedic medicinal herbs.

Stress and persistent overthinking can also interfere with sleep. For practical information about this connection, see our guide to insomnia related to overthinking.

Ashwagandha should not be considered a substitute for addressing everyday sources of stress. For a broader look at lifestyle factors associated with stress, see our article on stress, unhealthy lifestyle and busy living.

External Resources: 

For an evidence-based review of what clinical studies have found about ashwagandha for stress, anxiety and sleep, see the NIH Office of Dietary Supplements Ashwagandha fact sheet.

For detailed information about the potential benefits, side effects, medication interactions and precautions associated with ashwagandha, see the NCCIH Ashwagandha information page.