It is also not riskfree. Ashwagandha can cause digestive symptoms or drowsiness, has been linked to rare cases of liver injury, may affect thyroid function, and can interact with medicines. This guide explains what human research can and cannot tell us, how products differ, and what to consider before using one.
Key Takeaways
- Some ashwagandha preparations may modestly improve perceived stress and sleep, but studies are often small and use different extracts.
- Evidence for testosterone and sperm quality is limited; ashwagandha is not a proven testosterone treatment.
- Claims about major muscle growth, fat loss, or broad health benefits go beyond the available evidence.
- Short-term use has been studied more than long-term use. Rare liver injury and possible thyroid effects are important safety considerations.
- People who are pregnant or breastfeeding, have thyroid or autoimmune disorders, have liver disease, take interacting medicines, or are preparing for surgery should avoid self-prescribing it and discuss it with a clinician.
What Is Ashwagandha?
Withania somnifera is an evergreen shrub found in parts of India, Africa, and the Middle East. It has a long history of use in Ayurvedic medicine. The plant contains several compounds, including withanolides, but researchers have not established which compounds account for each potential effect in humans (NCCIH, 2023).
Root Powder, Root Extract, and Root-Plus-Leaf Products
Products may contain ground root, a concentrated root extract, leaf extract, or a combination of root and leaf. Extraction and manufacturing methods affect the final chemical profile. A milligram amount alone therefore does not tell you how comparable two products are.
Some supplements list a percentage of withanolides, compounds commonly used as quality markers. Standardization can improve consistency between batches, but it does not prove that a product is effective or safer than another formulation. Clinical findings apply most directly to the specific preparation studied, not automatically to every supplement sold under the same herb name (NCCIH, 2023).
How Might Ashwagandha Work?
Researchers are investigating whether ashwagandha influences the body's stress-response systems, including the hypothalamic-pituitary-adrenal (HPA) axis, and whether it affects processes involved in sleep and inflammation. Some proposed mechanisms come from laboratory or animal research. These findings can help generate hypotheses, but they do not establish that the same effects occur at meaningful levels in people.
Some human trials have reported lower cortisol levels alongside improvements in self-reported stress. Cortisol is a normal hormone with important roles in daily function; lowering it is not inherently beneficial for everyone. A biomarker change should not be treated as proof of a clinical benefit unless the study also demonstrates a meaningful improvement in health or functioning (Arumugam et al., 2024).
Ashwagandha Benefits: What Human Research Suggests
Research on ashwagandha is promising in a few areas, but the evidence base has important limitations. Studies frequently involve relatively small groups, short treatment periods, and different extracts and doses. Reviews can combine results, but they cannot remove weaknesses in the underlying trials (NCCIH, 2023).
Stress and Perceived Stress
Stress is one of the better-studied uses. A 2024 systematic review and meta-analysis included nine randomized controlled trials with 558 participants. It reported improvements in perceived stress scores and lower serum cortisol compared with placebo. The authors also noted that more information is needed about long-term safety (Arumugam et al., 2024).
These findings do not mean that ashwagandha reliably treats an anxiety disorder, depression, or burnout. Many trials measure self-reported symptoms over a limited period, and results may not generalize to people with diagnosed conditions. If stress is persistent or interfering with daily life, professional support and evidence-based care remain important.
Sleep Quality and Insomnia
A 2021 systematic review and meta-analysis pooled five randomized trials involving 400 adults. It found a small-to-moderate statistical improvement in sleep outcomes, with larger effects in some subgroups, including participants with insomnia and those taking the extract for at least eight weeks. The small number of trials and variation between them limit how confidently the result can be applied to every person or product (Cheah et al., 2021).
Ashwagandha should not be considered a proven treatment for sleep apnea, restless legs syndrome, or every cause of insomnia. Persistent sleep problems deserve assessment, especially when accompanied by loud snoring, gasping during sleep, severe daytime sleepiness, or a substantial change in mood.
Consistent sleep and wake times, a comfortable sleep environment, limiting late caffeine, and addressing stress are practical first steps. For chronic insomnia, ask a healthcare professional about cognitive behavioral therapy for insomnia (CBT-I), an evidence-based treatment.
Anxiety, Mood, and Fatigue
Some trials and reviews report reductions in anxiety-related scores, but findings are not definitive. The NCCIH notes that evidence for anxiety remains unclear, reflecting uncertainty about study quality, formulations, and the clinical importance of the results (NCCIH, 2023). Do not use ashwagandha as a substitute for prescribed treatment or professional mental health care.
Claims that it reliably improves energy, focus, or general well-being are less established. Fatigue can have many causes including insufficient sleep, anemia, medication effects, and medical conditions so persistent fatigue should not automatically be treated with a supplement.
Testosterone, Sperm Quality, and Fertility
Some studies suggest that taking ashwagandha for roughly two to four months may increase testosterone or improve selected semen measures in some men. However, the evidence is limited, and results should not be generalized to all men or interpreted as proof that the supplement treats infertility or low testosterone (NCCIH, 2023; Smith et al., 2021).
A testosterone result is affected by factors such as time of day, illness, sleep, medicines, and the testing method. Anyone with symptoms that could indicate low testosterone should seek an appropriate medical evaluation rather than trying to diagnose or treat the issue with a supplement. Fertility concerns also warrant clinical assessment; changes in a semen measure do not necessarily mean a higher chance of pregnancy.
Evidence for reproductive or hormonal benefits in women is insufficient to make broad claims. Ashwagandha should not be marketed as a general hormone-balancing treatment.
Strength, Muscle Growth, Recovery, and Fat Loss
A randomized trial published in 2015 studied 57 young men who were new to resistance training. Participants received a specific ashwagandha root extract or placebo during an eight-week training program. The study reported greater improvements in some strength and muscle-size measures in the supplement group, but it was a small trial and does not establish that all ashwagandha products improve performance (Wankhede et al., 2015).
The overall evidence is not strong enough to treat ashwagandha as a reliable muscle-building or sports-performance supplement. It has not been established as a direct fat burner, and claims of substantial body recomposition are not supported. Progressive resistance training, adequate dietary protein and energy intake, and sufficient sleep remain the foundations of muscle gain and recovery.
How Strong Is the Evidence?
| Claim | What the Evidence Suggests | Main Limitation |
|---|---|---|
| Perceived stress | Promising signal in some trials and reviews | Small studies, different preparations, uncertain long-term effects |
| Sleep | Possible modest improvement | Few trials and variable methods |
| Anxiety disorders | Not established as a treatment | Evidence remains unclear |
| Testosterone and sperm quality | Limited evidence of benefit in some men | Not proof of infertility treatment or universal hormone effects |
| Strength and muscle size | Some positive findings in small trials | Not enough evidence to guarantee performance benefits |
| Fat loss or broad disease treatment | Insufficient evidence | Marketing often exceeds clinical data |
This table summarizes the general state of the evidence rather than ranking every available extract. NCCIH notes that evidence is insufficient for several other promoted uses, including athletic performance and many medical conditions (NCCIH, 2023).
Ashwagandha Dosage: What Studies Do and Do Not Tell Us
There is no single universally established dose for ashwagandha. Trials use different preparations, concentrations, and schedules, so milligrams of one extract may not be equivalent to the same amount of another product. The 2021 sleep review found more noticeable effects in a subgroup taking at least 600 mg per day for at least eight weeks, but that subgroup finding is not a universal dosing recommendation (Cheah et al., 2021).
Do not copy a dose from a study without checking whether the extract, plant part, and concentration match the product being considered. Higher doses are not automatically more effective and may increase the chance of adverse effects. Follow the product label only after a clinician or pharmacist has reviewed whether it is appropriate for you, particularly if you take medication or have a health condition.
What to Look for on a Label
- Plant part: Check whether the product uses root, leaf, or a combination.
- Extract details: Look for the extract amount and any stated standardization. A withanolide percentage is a marker, not proof of clinical effectiveness.
- Transparent serving information: Avoid products that obscure the amount in a proprietary blend.
- Independent quality testing: Where available, look for credible third-party verification of identity and quality. Testing may reduce some quality concerns but cannot establish that the supplement will work or eliminate all risks.
- Realistic marketing: Be skeptical of promises to cure anxiety, normalize hormones, melt fat, or build muscle rapidly.
In the United States, dietary supplements are not approved by the FDA for effectiveness before they are marketed. Manufacturers are responsible for meeting applicable requirements, and regulators can act when safety or compliance concerns arise (NCCIH, 2023).
Ashwagandha Side Effects and Safety Risks
Common Side Effects
Reported side effects include stomach upset, nausea, diarrhea, vomiting, and drowsiness. Stop taking the product and seek advice if symptoms are significant or persistent. Short-term use has been studied more than long-term use; safety beyond about three months is not well established (NCCIH, 2023).
Liver Injury
Rare cases of clinically apparent liver injury have been associated with ashwagandha supplements. LiverTox, a resource from the National Institute of Diabetes and Digestive and Kidney Diseases, describes reported cases and advises avoiding ashwagandha in people with cirrhosis or advanced chronic liver disease (NIDDK, 2024).
Stop taking ashwagandha and seek urgent medical assessment if you develop yellowing of the skin or eyes, dark urine, unusually pale stools, severe or persistent abdominal pain, or unexplained intense itching. Do not restart it after suspected supplement-related liver injury unless a qualified clinician specifically advises you.
Thyroid and Autoimmune Conditions
Ashwagandha may affect thyroid function and is not recommended by NCCIH for people with thyroid disorders. It may also be unsuitable for people with autoimmune conditions because of possible effects on immune function. People with these conditions should not experiment with it without specialist advice (NCCIH, 2023).
Medicine Interactions
Ashwagandha may interact with medicines for diabetes or high blood pressure, thyroid hormone medicines, sedatives, anticonvulsants, and immunosuppressants. It may also be inappropriate for people with hormone-sensitive prostate cancer. Ask a pharmacist or clinician to review all prescription medicines, over-the-counter products, and supplements before use (NCCIH, 2023).
Pregnancy, Breastfeeding, Surgery, and Liver Disease
Ashwagandha should be avoided during pregnancy and should not be used while breastfeeding. NCCIH also advises against use before surgery. People with liver disease—particularly cirrhosis or advanced chronic liver disease should avoid it because of the potential for liver injury (NCCIH, 2023; NIDDK, 2024).
When to Get Medical Advice
Discuss ashwagandha with a healthcare professional before use if you take medication, have a chronic condition, are considering it for a diagnosed mental health or hormonal problem, or are planning surgery. Seek medical care rather than self-treating persistent anxiety, sleep problems, unexplained fatigue, fertility concerns, or symptoms that may indicate a thyroid or liver problem.
Frequently Asked Questions
Does Ashwagandha Work?
Some preparations may modestly improve perceived stress and sleep, but results vary and evidence is limited for many other claims. Product formulation and study quality matter (NCCIH, 2023; Cheah et al., 2021).
How Long Does Ashwagandha Take to Work?
Studies typically assess outcomes after several weeks rather than after a single dose. There is no guaranteed timeline, and the results of a particular trial may not apply to another formulation. Do not increase the dose to try to speed up results.
Does Ashwagandha Increase Testosterone?
Limited evidence suggests it may increase testosterone in some men over a period of months, but it is not a proven treatment for low testosterone and is not expected to affect everyone the same way (NCCIH, 2023; Smith et al., 2021).
Can Ashwagandha Help Build Muscle or Burn Fat?
A small resistance-training trial reported improvements in selected strength and muscle-size measures, but the evidence is not sufficient to promise meaningful muscle growth. Ashwagandha has not been established as a fat-loss supplement (Wankhede et al., 2015; NCCIH, 2023).
Can Ashwagandha Cause Liver Damage?
Rare cases of liver injury have been reported. Stop taking it and seek medical assessment if you develop jaundice, dark urine, or other concerning symptoms. People with advanced liver disease should avoid it (NIDDK, 2024).
Is Ashwagandha Safe to Take Every Day?
Daily use has been studied in short-term trials, but long-term safety is uncertain. It may cause side effects and interact with medicines, so daily use is not appropriate for everyone (NCCIH, 2023).
Conclusion
Ashwagandha is a traditional herb with early clinical evidence suggesting possible benefits for perceived stress and sleep. Findings related to testosterone, fertility, and strength are more limited, while claims about fat loss and broad medical benefits remain unproven. Differences between extracts make it difficult to apply one study's results to every product.
Safety deserves equal attention to potential benefits. Ashwagandha can cause digestive symptoms and drowsiness, has been linked to rare liver injury, may affect thyroid function, and can interact with medicines. If you are considering it, review your health history and medications with a qualified clinician rather than relying on marketing claims.
References
- National Center for Complementary and Integrative Health (NCCIH). (2023). Ashwagandha. National Institutes of Health. https://www.nccih.nih.gov/health/ashwagandha. Used for evidence summaries, product variability, and safety guidance.
- Cheah, K. L., Norhayati, M. N., Yaacob, L. H., & Abdul Rahman, R. (2021). Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS ONE, 16(9), e0257843. https://doi.org/10.1371/journal.pone.0257843. PubMed record and abstract reviewed; the article is available through the linked open-access record.
- Arumugam, V., Vijayakumar, V., Balakrishnan, A., Bhandari, R. B., Boopalan, D., Ponnurangam, R., Thirupathy, V. S., & Kuppusamy, M. (2024). Effects of Ashwagandha (Withania somnifera) on stress and anxiety: A systematic review and meta-analysis. Explore, 20(6), 103062. https://doi.org/10.1016/j.explore.2024.103062. PubMed abstract and bibliographic record reviewed.
- Smith, S. J., Lopresti, A. L., Teo, S. Y. M., et al. (2021). Examining the effects of herbs on testosterone concentrations in men: A systematic review. Advances in Nutrition, 12(3), 744–765. https://pubmed.ncbi.nlm.nih.gov/33150931/. PubMed abstract and bibliographic record reviewed.
- Wankhede, S., Langade, D., Joshi, K., Sinha, S. R., & Bhattacharyya, S. (2015). Examining the effect of Withania somnifera supplementation on muscle strength and recovery: A randomized controlled trial. Journal of the International Society of Sports Nutrition, 12, 43. https://doi.org/10.1186/s12970-015-0104-9. Publisher page and PubMed record reviewed; full text could not be reliably opened during this review.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (2024). Ashwagandha. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. https://www.ncbi.nlm.nih.gov/books/NBK548536/. Official NCBI bibliographic summary reviewed for liver-injury reports and clinical cautions.
