Ashwagandha: Benefits, Uses and Side Effects

By Matthew Atkins · Oct 30, 2026

Ashwagandha

Ashwagandha (Withania somnifera) is a small evergreen shrub in the nightshade family, native to India, the Middle East, and North Africa, whose root and leaves contain withanolides—steroidal lactones that modulate stress-response pathways. Ashwagandha is one of several adaptogenic herbs, used traditionally in Ayurveda and clinically studied for reducing stress, anxiety, and cortisol.

What Is Ashwagandha?

Ashwagandha is the common name for Withania somnifera, a small evergreen shrub in the nightshade family (Solanaceae) that grows one to two meters tall, with dull green elliptic leaves, bell-shaped flowers, and bright red berries enclosed in a papery calyx. The name derives from Sanskrit for “smell of the horse,” referring both to the fresh root’s distinct odor and the traditional belief that it imparts strength and vigor. Native to the dry regions of India, the Middle East, and parts of North Africa, this drought-tolerant plant thrives in arid, sandy soils and has been cultivated for centuries in northwestern Indian states such as Rajasthan, Madhya Pradesh, and Gujarat. In Western herbalism, it is often called “Indian ginseng” for its adaptogenic tonic role, though it is not botanically related to true ginseng.

Withanolides

Withanolides are naturally occurring steroidal lactones built on an ergostane skeleton with a distinctive lactone ring, serving as the primary drivers of ashwagandha’s bioactivity. Researchers have identified dozens of distinct withanolides in the root and leaf tissues, with withaferin A and withanolide D among the most extensively studied.

Withanolide concentrations and profiles vary depending on the plant part used, age at harvest, growing conditions, and extraction method. Because these compounds carry the plant’s therapeutic signature, supplement manufacturers commonly standardize extracts to a defined withanolide percentage.

At the cellular level, withanolides modulate inflammatory signaling, influence stress-response mechanisms, bolster antioxidant defenses against oxidative stress, and interact with receptors and enzymes involved in immune regulation. Withaferin A in particular binds specific protein targets tied to the herb’s adaptogenic and restorative effects.

Root vs. Leaf Extracts

Traditional Ayurvedic preparations rely almost exclusively on the root. Root tissue contains a complex blend of withanolides, alkaloids, and sitoindosides, with the withanolide fraction typically ranging from 0.3 to 1 percent in quality extracts. This phytochemical profile develops slowly, reaching its richest concentration when roots are harvested after eighteen months to two years.

Leaves grow quickly and contain higher absolute levels of certain withanolides—particularly withaferin A, which can reach concentrations several times higher than in the root. Manufacturers often favor leaves because they are cheaper to harvest and yield high withanolide percentages on paper, but the chemical spectrum is narrower and skewed heavily toward withaferin A.

This chemistry shapes safety. Withaferin A has documented cytotoxic properties at higher doses, raising questions about the long-term tolerability of leaf-heavy extracts. Standardized root extracts, used at traditional doses of 300 to 600 milligrams daily, have a much longer record of human tolerability in clinical trials. When reading a label, check whether the product specifies “root extract,” “root and leaf,” or leaf-only material.

Ashwagandha in Ayurvedic Medicine

For a broader background on the tradition, see this beginner’s guide to Ayurveda, where ashwagandha has been used for thousands of years as a Rasayana*—a class of rejuvenative herbs believed to nourish the body’s deepest tissues and promote longevity and vitality. Classical texts such as the Charaka Samhita and Sushruta Samhita praise its ability to restore strength, improve stamina, and help the body withstand physical and mental stress.

Ayurvedic theory frames health as a balance among three bodily humors, or doshas: vata, pitta, and kapha. Ashwagandha is classified as a warming, grounding herb particularly valued for pacifying excess vata, which governs movement and the nervous system and is associated with nervousness, restlessness, anxiety, insomnia, and fatigue. It was also considered supportive for building ojas, a subtle essence linked to immunity, vigor, and resilience.

Traditionally prepared as powders mixed with warm milk or ghee, decoctions, or medicated pastes—often in compound formulas—it was prescribed to convalescents, the elderly, and those recovering from exhaustion, as well as to support reproductive health.

Ashwagandha Benefits

Over the past two decades, randomized controlled trials and systematic reviews have evaluated whether ashwagandha’s traditional uses hold up under clinical scrutiny, including a widely cited 2019 systematic review that found moderate evidence for reducing stress and anxiety. Across this literature, important methodological caveats apply: most trials are short in duration, enroll small sample sizes, use varying proprietary formulations, and test doses ranging from roughly 250 to 600 milligrams per day. While clinical evidence supports several applications, larger, longer, and better-standardized trials remain necessary to confirm these findings.

Stress, Anxiety and Cortisol

Chronic stress activates the hypothalamic-pituitary-adrenal (HPA) axis, elevating serum cortisol levels in ways that disrupt mood, sleep, and immune function. Ashwagandha acts as an adaptogen, helping the body maintain homeostasis by modulating HPA axis activity and attenuating the stress response.

In randomized controlled trials, adults experiencing chronic stress who took standardized root extract (including a widely cited 60-day trial) showed significant reductions in perceived stress scores, anxiety symptoms, and serum cortisol compared to placebo. By blunting prolonged cortisol exposure, the herb may ease stress-related fatigue, irritability, and difficulty concentrating.

Sleep

Clinical trials using both subjective questionnaires and objective actigraphy measurements report that standardized ashwagandha root extract improves overall sleep quality, feelings of refreshment upon waking, and sleep efficiency compared with placebo. Rather than acting as a direct sedative, the herb appears to help the nervous system settle into a more restorative pattern by lowering physiological arousal and bedtime anxiety.

Studies also document reductions in sleep onset latency—the time it takes to fall asleep after going to bed—and fewer nighttime awakenings among participants with insomnia or stress-related sleep complaints. Benefits typically build over several weeks of consistent use.

Muscle Strength and Exercise Recovery

Several randomized controlled trials lasting eight to twelve weeks suggest ashwagandha supports both resistance and endurance training at doses of 300 to 600 milligrams daily. In one eight-week study of resistance-training men, those taking ashwagandha achieved significantly greater gains in bench press and leg extension strength, alongside larger increases in arm and chest muscle circumference, compared with placebo. A separate trial reported improvements in VO2 max, the standard measure of aerobic capacity and cardiovascular efficiency.

For exercise recovery, studies have found lower post-exercise levels of creatine kinase—an enzyme that leaks from damaged muscle fibers—along with reduced muscle soreness and faster return to normal function. Researchers link this to lower cortisol levels, since elevated stress hormones can impede tissue repair and blunt training adaptations.

Testosterone and Male Fertility

In a randomized, placebo-controlled trial of healthy but stressed men, eight weeks of standardized ashwagandha root extract produced meaningful increases in serum testosterone alongside reductions in cortisol. Researchers propose that calming the HPA axis reduces the suppressive effect chronic stress exerts on testosterone production, though the precise mechanism remains under investigation.

In trials involving men with low sperm count or unexplained infertility, several weeks of supplementation improved sperm concentration, total sperm count, forward motility, semen volume, and sperm morphology relative to controls. Preliminary research also suggests reductions in seminal oxidative stress and shifts in luteinizing hormone and follicle-stimulating hormone. Men considering ashwagandha for fertility should consult a healthcare provider, as sample sizes in these trials have been modest.

Energy and Fatigue

Unlike caffeine or other nervous system stimulants, ashwagandha does not raise heart rate or blood pressure, nor does it cause jitteriness, dependency, or withdrawal. Instead, it addresses fatigue tied to chronic stress and HPA axis overload by preventing the cortisol spikes and crashes that drain daily stamina.

At the cellular level, research suggests it may improve mitochondrial efficiency and reduce oxidative stress, supporting steady energy production and calm alertness during prolonged physical or mental exertion.

Focus and Memory

Trials in healthy adults have reported improvements in attention, concentration, working memory, information processing speed, and executive function—higher-order prefrontal cortex skills such as planning, decision-making, task switching, and impulse control—along with faster reaction times after several weeks of supplementation.

In laboratory and animal studies, root compounds have helped defend brain cells against oxidative stress and inflammation while supporting the health of dendrites and synaptic connections. Whether these neuroprotective findings translate to age-related cognitive resilience in humans requires further clinical study.

Mood

Small, short-term clinical trials have noted improvements on standardized mood questionnaires and reductions in depressive symptoms among participants taking ashwagandha over several weeks. Beyond lowering cortisol, compounds in the herb appear to interact with central neurotransmitter pathways, particularly GABA—the brain’s primary inhibitory neurotransmitter, which acts as a brake on excessive nervous activity—and serotonin, which regulates emotional stability and well-being.

Ashwagandha is not a replacement for established depression or anxiety treatments, and anyone experiencing persistent low mood should consult a healthcare provider.

Other Claimed Benefits (Limited Evidence)

Several other proposed benefits rest mainly on laboratory, animal, or small preliminary human studies:

• Blood sugar regulation: Preclinical experiments and small human trials suggest ashwagandha may influence glucose metabolism, insulin sensitivity, and fasting blood glucose, but human results have been inconsistent and too limited to establish reliable glycemic control.
• Immune modulation: Laboratory and animal models show withanolides can influence cytokine production and immune cell proliferation, though clinical relevance in humans remains unclear.
• Anticancer properties: While cell culture and animal studies have explored whether ashwagandha constituents inhibit tumor growth, no human clinical trials establish any anticancer benefit, and it must not be used to treat cancer.

Ashwagandha for Women

By moderating HPA axis activity and cortisol, ashwagandha may help buffer the delicate interplay of estrogen and progesterone against chronic stress, supporting menstrual regularity and stress-related reproductive health.

This endocrine support is particularly relevant during perimenopause, when fluctuating estrogen and progesterone levels trigger mood swings, sleep disturbances, fatigue, and irritability. Studies suggest ashwagandha may ease these transitional symptoms while supporting sexual desire (libido), which is often blunted by exhaustion, high cortisol, and shifting reproductive hormones.

How to Take Ashwagandha

Choosing an ashwagandha supplement involves selecting a delivery format and extract type that fit your routine and taste preferences. Pairing your dose with an existing daily habit—such as morning coffee or evening tea—or using a pill organizer helps maintain consistency.

Capsules, Powders, Gummies and Liquids

• Capsules and tablets: Provide a precise, standardized dose, protect compounds from oxidation, and mask the herb’s bitter taste. They are portable and convenient, though more expensive per gram than bulk powder.
• Powders: Made from ground root or concentrated extract, powders are the most economical option and preserve the full spectrum of root constituents. They have a distinctly earthy, bitter flavor and gritty texture, and their fat-soluble compounds absorb best when mixed with fats like milk or ghee.
• Gummies: Palatable and easy to take for those who dislike swallowing pills, but they often contain added sugar and lower extract concentrations, and manufacturing heat may degrade some active compounds.
• Liquids and tinctures: Alcohol- or glycerin-based dropper extracts absorb quickly through the mucous membranes and allow flexible dosing by the drop, though they cost more per dose and require careful storage.

KSM-66 vs. Sensoril and Other Branded Extracts

Branded extracts offer consistent standardization compared to generic products, which often fail to disclose plant parts or withanolide percentages:

• KSM-66: A root-only extract standardized to about 5 percent withanolides, produced using a green-chemistry process without alcohol or harsh solvents. It keeps alkaloid content consistent and closely mirrors the root preparations used in most clinical trials.
• Sensoril: Combines both root and leaf material and is standardized to a higher concentration—typically around 10 percent withanolides—allowing for smaller serving sizes and capsules, though with a different phytochemical profile than root-only extracts.

Traditional Ashwagandha Milk (Moon Milk)

In Ayurveda, simmering ashwagandha in milk with healthy fats and spices is a classic evening ritual taken about an hour before bed:

1. Whisk 1/2 to 1 teaspoon of ashwagandha root powder into a small amount of warm water to form a smooth paste that prevents clumping.
2. Warm 1 cup of whole milk (or almond or oat milk) in a saucepan over low to medium heat.
3. Stir in the ashwagandha paste, a pinch of ground cinnamon, a small piece of crushed cardamom, a few strands of saffron, and a tiny pinch of black pepper (traditionally used to aid bioavailability).
4. Add 1 teaspoon of ghee or coconut oil to help absorb fat-soluble constituents, and simmer gently for 5 to 10 minutes.
5. Remove from heat, strain if desired, let cool slightly, and stir in 1 teaspoon of honey or jaggery before sipping slowly.

Ashwagandha Dosage

Clinical studies typically use between 300 mg and 1,000 mg of standardized root extract daily, depending on the target outcome:

• Stress and mood support: 300 mg to 600 mg per day.
• Sleep quality: Around 600 mg per day.
• Physical performance, stamina, and recovery: 500 mg to 1,000 mg per day, often split into two doses.

Because extract strengths vary, check the label for both the withanolide percentage and equivalent raw root weight, and start at the lower end of the dose range to assess tolerance.

Best Time of Day to Take It

You can take ashwagandha in the morning, in the evening, or split between both. A morning dose with breakfast suits those seeking daytime stress resilience, while an evening dose with dinner or before bed complements a wind-down routine and avoids any daytime drowsiness. If taking it on an empty stomach causes mild digestive discomfort, always pair your dose with a meal. Ultimately, daily consistency matters more than the specific hour.

How Long Does Ashwagandha Take to Work?

Ashwagandha works on a two-speed timeline. Some users notice a subtle sense of calm or reduced tension within the first few hours to a few days of taking a standardized extract.

However, deeper adaptogenic benefits—such as measurable drops in cortisol, improved stress resilience, and steadier sleep—build gradually. In clinical trials, significant changes typically emerge between four and twelve weeks of daily use. Commit to at least eight weeks while tracking energy, mood, and sleep before judging its effectiveness.

Should You Cycle Ashwagandha?

Many herbalists and long-term users practice cycling—taking scheduled breaks from the herb—to prevent tolerance, allow physiological systems to recalibrate toward homeostasis, and evaluate how they feel without it. Common cycling schedules include:

• Five days on, two days off each week.
• Several weeks on, followed by one week off.
• Two to three months of daily use, followed by a two- to four-week break.

Side Effects and Safety

In clinical trials lasting eight to twelve weeks, ashwagandha is generally well tolerated by healthy adults at standard doses, with low dropout rates. Long-term human safety data beyond three months remain limited, however, and rare but serious adverse events—along with specific risks for vulnerable groups—warrant attention.

Common Side Effects

Mild, transient side effects most often involve the digestive tract during the first few weeks of use, including nausea, stomach cramping, bloating, heaviness, and loose stools or mild diarrhea. Taking the supplement with food or lowering the dose usually resolves these complaints.

Some users also experience headaches, dizziness, or daytime drowsiness and mental fog. Because ashwagandha can be sedating, note how it affects you before driving or operating machinery, and avoid combining it with alcohol.

Liver Safety

Post-marketing surveillance and published case reports have documented rare instances of drug-induced liver injury in otherwise healthy people taking ashwagandha for a few weeks to several months. Affected individuals developed sharp elevations in serum transaminases—alanine aminotransferase (ALT) and aspartate aminotransferase (AST), sometimes exceeding ten times the upper limit of normal—alongside symptoms such as unusual fatigue, persistent nausea, abdominal discomfort, jaundice (yellowing of the skin or eyes), dark urine, and pruritus (itching).

Most cases resolved within weeks to months after stopping the supplement. Proposed causes include idiosyncratic reactions, genetic variations in hepatic metabolism, or product contamination and adulteration. Anyone with pre-existing liver conditions (such as chronic hepatitis, cirrhosis, or fatty liver disease) should avoid ashwagandha or undergo baseline and periodic liver enzyme monitoring under medical supervision. If symptoms of liver distress appear, stop use immediately and seek medical evaluation.

Thyroid Effects

Ashwagandha can stimulate the thyroid gland to synthesize more hormone, raising circulating levels of T3 and T4. Small studies in people with subclinical hypothyroidism have observed rises in thyroid hormone concentrations alongside improvements in energy, mood, and cold intolerance.

Conversely, in people with hyperthyroidism or Graves’ disease, further hormone stimulation can aggravate the condition and intensify heart palpitations, anxiety, restlessness, heat intolerance, and unintentional weight loss. Anyone with a thyroid disorder should consult a physician before use so hormone levels can be monitored.

Autoimmune Conditions

Because laboratory and animal studies suggest ashwagandha can stimulate natural killer cell function and antibody production, it carries theoretical risks for people with autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, Hashimoto’s thyroiditis, and multiple sclerosis. Activating an already misdirected immune system could trigger symptom flare-ups or worsen disease activity, so patients should consult their specialist before taking it.

Drug Interactions

Ashwagandha can interact with several classes of prescription medications:

• Sedatives and CNS depressants: Can compound drowsiness and slow reaction times when combined with benzodiazepines, prescription sleep aids, anticonvulsants, or certain antidepressants.
• Thyroid medications: Combining ashwagandha with levothyroxine or other thyroid replacements can push hormone levels too high.
• Immunosuppressants: Immune-stimulating effects may counteract drugs used for autoimmune conditions or after organ transplants, such as corticosteroids, methotrexate, biologics, tacrolimus, or cyclosporine.
• Antihypertensives (blood pressure drugs): Ashwagandha may lower blood pressure on its own; pairing it with blood pressure medications can cause readings to drop too low, leading to dizziness or faintness.
• Diabetes medications: Because the herb may lower blood glucose, combining it with glucose-lowering drugs increases the risk of hypoglycemia.

Always consult your prescribing doctor or pharmacist before combining ashwagandha with prescription drugs.

Pregnancy and Breastfeeding

Traditional Ayurvedic texts classify ashwagandha as having abortifacient potential capable of stimulating uterine contractions, and modern clinical guidance advises against its use at any stage of pregnancy.

Because no human studies establish whether withanolides pass into breast milk or how they might affect a nursing infant, breastfeeding women should also avoid the herb. Check multi-ingredient stress and sleep supplement labels carefully, as ashwagandha is frequently included in proprietary blends.

Why Some Countries Restrict Ashwagandha

Regulatory agencies in several countries have restricted or scrutinized ashwagandha. Denmark banned the sale of ashwagandha products after food safety officials concluded that available research could not establish a safe daily upper intake level, citing concerns over endocrine and reproductive effects as well as poorly documented leaf extracts. Other European Union member states have issued similar warnings or withdrawn certain products, applying strict food-safety evidentiary standards rather than relying on traditional use.

Who Should Avoid Ashwagandha

In addition to those listed in the sections above, several specific groups should avoid ashwagandha or use it only under direct medical supervision:

• Pregnant and breastfeeding women.
• People with hyperthyroidism, liver disease, or autoimmune conditions.
• Individuals taking sedatives, thyroid hormones, immunosuppressants, antihypertensives, or diabetes medications.
• People with nightshade sensitivities: As a member of the Solanaceae family, ashwagandha may trigger reactions in those intolerant to nightshades.
• People with hormonally sensitive cancers: Due to its endocrine and testosterone-modulating activity, those with hormonally sensitive prostate or breast cancers should avoid it.
• Surgical patients: Stop taking ashwagandha at least two weeks before scheduled surgery, as it may potentiate anesthesia and affect blood sugar and blood pressure during the procedure.

How to Buy Quality Ashwagandha

Because dietary supplements are not regulated like pharmaceuticals, use the following criteria to evaluate product quality:

• Third-party testing: Look for independent verification seals or certificates of analysis (COAs) from organizations like USP, NSF, or ConsumerLab confirming that the contents match the label.
• Heavy metal screening: Ashwagandha roots can absorb lead, arsenic, mercury, and cadmium from soil. Reputable brands test every batch for heavy metals and disclose the country of origin and cultivation practices.
• Clear standardization and plant part disclosure: Choose supplements that specify root-only (or clearly labeled root-and-leaf) extracts standardized to a stated withanolide percentage (commonly 2.5 to 5 percent for root extracts) rather than unstandardized powders or undisclosed leaf blends.

Ashwagandha FAQ

Is ashwagandha habit-forming? No. Ashwagandha does not act on brain reward pathways, does not cause physical dependence, and can be discontinued without withdrawal symptoms.

Can ashwagandha cause emotional blunting? While not widely documented in clinical trials, some sensitive users report feeling emotionally flat or unmotivated after taking ashwagandha, possibly due to lowered cortisol or shifts in neurotransmitter signaling. Lowering the dose or cycling off the herb typically resolves this effect.

Does ashwagandha help with weight loss? Ashwagandha is not a direct weight-loss supplement, and readers exploring metabolic support may want to review shilajit benefits and uses separately. It may indirectly support weight management in chronically stressed individuals by curbing stress-related eating and improving sleep, though clinical findings on body fat and metabolic markers remain mixed.

What can you stack with ashwagandha? Common supplement pairings include rhodiola or holy basil (tulsi) for daytime stress resilience, and magnesium for evening relaxation. When combining supplements, introduce one at a time at a low dose to monitor how your body responds.

Frequently Asked Questions

How much ashwagandha should I take per day?

Clinical studies typically use between 300 mg and 1,000 mg of standardized root extract daily, depending on the target outcome. For stress and mood support, the article lists 300 mg to 600 mg per day; for sleep quality, around 600 mg per day; and for physical performance, stamina, and recovery, 500 mg to 1,000 mg per day, often split into two doses. It also advises starting at the lower end of the dose range to assess tolerance.

Does ashwagandha help with sleep?

Clinical trials report that standardized ashwagandha root extract improves overall sleep quality, feelings of refreshment upon waking, and sleep efficiency compared with placebo. Studies also document reductions in sleep onset latency and fewer nighttime awakenings, with benefits typically building over several weeks of consistent use.

What is the difference between ashwagandha root and leaf extract?

Traditional Ayurvedic preparations rely almost exclusively on the root, and standardized root extracts used at traditional doses of 300 to 600 mg daily have a much longer record of human tolerability in clinical trials. Leaves contain higher absolute levels of certain withanolides—particularly withaferin A—but the chemical spectrum is narrower and skewed heavily toward withaferin A. The article notes that withaferin A has documented cytotoxic properties at higher doses, raising questions about the long-term tolerability of leaf-heavy extracts.

Is ashwagandha safe if you have thyroid problems?

Ashwagandha can stimulate the thyroid gland to synthesize more hormone, raising circulating T3 and T4. In people with hyperthyroidism or Graves’ disease, this can aggravate the condition and intensify heart palpitations, anxiety, restlessness, heat intolerance, and unintentional weight loss. Anyone with a thyroid disorder should consult a physician before use so hormone levels can be monitored.

Can you take ashwagandha while pregnant or breastfeeding?

The article advises against ashwagandha use at any stage of pregnancy because traditional Ayurvedic texts classify it as having abortifacient potential capable of stimulating uterine contractions. Breastfeeding women should also avoid the herb because no human studies establish whether withanolides pass into breast milk or how they might affect a nursing infant.

How long does ashwagandha take to work?

Ashwagandha works on a two-speed timeline: some users notice a subtle sense of calm or reduced tension within the first few hours to a few days. Deeper adaptogenic benefits build gradually, with significant changes typically emerging between four and twelve weeks of daily use in clinical trials. The article recommends committing to at least eight weeks while tracking energy, mood, and sleep before judging effectiveness.

Matthew Atkins

Matthew studied biology and has worked in conservation. He's been interested in medicinal herbs for many years. More about HerbsList

This page is for general information only and isn't medical advice. Talk with a doctor or pharmacist before taking any herb or supplement. Full disclaimer