Ashwagandha: Extracts, Small Benefits, and Real Safety Limits

What is ashwagandha?

Ashwagandha comes from the root of Withania somnifera, a native plant in the Middle East and North Africa, other African regions, southern Europe, the Indian subcontinent, and Southeast Asia. It is used in Ayurveda.

People usually take it for stress or sleep. It is also sold for sexual health, sperm quality, testosterone and memory; the research differs substantially by outcome and preparation. The most studied and sold amounts are roughly 300–600 mg a day of the KSM-66 extract form.

KSM-66 is the most familiar root-only extract. Shoden is a different concentrated extract, and Sensoril is a root-plus-leaf extract.

How was ashwagandha used traditionally?

Ashwagandha root has been used in Ayurveda and Unani medicine for strength, restoration and reproductive health. The Indian Ministry of Ayush and CCRAS describe it as a rasayana, a category concerned with rejuvenation and maintaining health, and document aphrodisiac use alongside uses for musculoskeletal, neurological, skin and respiratory complaints. Their 2024 dossier^[1] also lists root-powder preparations in Ayurveda, Siddha and Unani pharmacopoeias. This is an institutional account of those traditions; the original ancient passages have not been independently checked here.

Today's capsules may contain root extract, leaf extract or both. The NIH Office of Dietary Supplements^[2] notes that root and leaf differ chemically. A concentrated named extract therefore needs its own evidence. Modern studies of stress, strength, sexual function or semen quality address parts of the older uses, while the broader promise of rejuvenation remains a separate question.

Why do people take ashwagandha?

An adult considering Ashwagandha for stress or sleep should know that the checked trials of specific extracts generally lasted 8 to 10 weeks; longer-term safety remains uncertain. Pregnancy, liver or thyroid disease, upcoming surgery, and interacting medicines can make self-experimentation with Ashwagandha problematic. Switching between KSM-66, Shoden, Sensoril, and powder is also problematic because the dosages are not interchangeable. Most people should not take ashwagandha as a default daily supplement. It has no recommended daily amount, and not taking it does not create a deficiency.

Keep in mind that ashwagandha may not work for everyone, or may work differently for different people. While some people find that it makes them feel calmer or less stressed, others report feeling more anxious.

When to ask a doctor before taking it

Ask your doctor before taking ashwagandha if you have liver disease, thyroid disease, an autoimmune condition, or hormone-sensitive prostate cancer, or if an operation is coming up. The National Center for Complementary and Integrative Health (NCCIH) also lists possible interactions with thyroid hormone, sedatives, anticonvulsants, immunosuppressants, and medicines for diabetes or blood pressure. Your doctor should set any schedule around those conditions or medicines.

New yellowing of the skin or eyes or marked itching is a reason to stop and seek prompt medical care. If you already have thyroid disease, contact the clinician managing it if you have new symptoms of racing heartbeat, shaking, unusual heat intolerance, or a marked change in your usual symptoms.

Ashwagandha forms at a glance

Skip an unnamed “clinically studied” product, a powder serving presented as equivalent to KSM-66, or a supplement with a label that doesn't identify the plant part, extract name, or full serving amount.

What to look for on the label

Which number on the label is the actual amount?

“Ashwagandha 600 mg” on the front could describe KSM-66, Shoden, Sensoril, or powder. Check the serving size first, then the ingredient name, plant part, extract name, milligrams per serving, and any stated withanolide percentage.

Withanolides are plant chemicals commonly used to describe an extract’s concentration. Equal percentages do not establish equal effects between extracts.

Misleading labels

Powder weight and extract weight

If you're considering buying a product that says 1,000 mg ashwagandha and the Supplement Facts line identifies plain powder, that number is the powder weight. It does not equal 1,000 mg of KSM-66 and does not carry a known KSM-66 withanolide amount.

Confusing servings and items per serving

A label with 180 capsules can provide 180 one-capsule servings, 90 two-capsule servings, or 60 three-capsule servings. Compare the milligrams in the full serving.

“Clinically studied” claims without a named extract

An unnamed 600 mg serving should not borrow the evidence for KSM-66 simply because the number looks familiar. KSM-66 is a named root extract; an unspecified powder or blend may have a different composition.

Common Myths about Ashwagandha

Does ashwagandha raise testosterone like a steroid?

No. A small eight-week trial in 50 untrained young men found a larger testosterone change when KSM-66 was added to resistance training than with training plus placebo. That result does not show that ashwagandha replaces testosterone treatment, and a second study did not find a testosterone difference from placebo.

Do mild side effects in short trials prove it is safe for the liver?

No. Short trials mostly recorded mild events, but they were too small and short to measure a rare liver injury rate. NCCIH reports rare cases of liver injury linked to ashwagandha supplements.

Is ashwagandha a proven memory supplement?

NCCIH says there is not enough evidence to determine whether ashwagandha helps cognitive function.

Drawbacks and side effects

NCCIH describes use for up to about three months as possibly safe for many adults; longer use has unknown safety. Drowsiness may affect the time when you should take it, but it's an individual factor, and trials have not established a best time to take Ashwagandha. There's also no recommendation for taking it with food or around meals.

There is no established milligram ceiling that separates a safe amount of ashwagandha from too much.

Ashwagandha during pregnancy and breastfeeding

Women who are pregnant or breastfeeding should avoid ashwagandha. NCCIH advises against use in both situations, and Germany's Federal Institute for Risk Assessment also advises against ashwagandha supplements during pregnancy and lactation while noting historical use to induce abortion.

There is no randomized pregnancy study that establishes a safe extract, dose, or duration.

The science behind ashwagandha

Stress and cortisol

Cortisol is a hormone made by the adrenal glands that helps your body respond to stress.

In one 60-day study, 64 adults with chronic stress received either KSM-66 at 300 mg twice a day or a placebo; 61 finished. Stress scores fell 44.0% with KSM-66 and 5.5% with placebo, while cortisol fell 27.9% and 7.9%, respectively. The groups started with different average stress scores, which complicates the comparison. Ixoreal, the company that makes KSM-66, supplied the extract, and the study followed one site for only two months.

Sleep

A 2021 review covered five randomized trials involving about 400 distinct adults and reported an overall sleep improvement. Its combined calculation reused some participants' results across several sleep outcomes, however, without clearly accounting for that overlap, so the overall effect and its precision need rechecking. The review's separate sleep-quality and time-in-bed estimates included no clear difference. The extracts, amounts, and study durations also differed.

One ten-week KSM-66 study used a wrist movement monitor to measure how long people took to fall asleep. The average was about 29 minutes with the extract and about 34 minutes with placebo. That observed difference was modest; the study's participant counts also conflict across its report.

Anxiety

A review of 12 trials with 1,002 participants found a large average difference in anxiety scores, but results varied sharply and the reviewers rated their certainty as low. NCCIH still describes the anxiety evidence as unclear rather than treating that average as proof of an anxiety medicine.

Testosterone and training

In an eight-week training study, untrained young men took KSM-66 at 300 mg twice a day or a placebo while both groups lifted weights. The testosterone change was about 96 ng/dL with KSM-66 and 18 ng/dL with placebo, and bench-press strength rose by about 46 kg versus 26 kg. Leg-extension gains were about 14.5 kg versus 9.8 kg. These were gains during a shared training program, not results from taking the extract alone. Fifty men finished the trial, and Ixoreal supplied the extract.

In a separate 60-day Shoden study at 240 mg a day, testosterone rose over time in men but did not beat placebo. The newer male sexual-health trials discussed below also differ: the 2025 trial found a larger testosterone change with KSM-66, while the 2026 trial did not find a clear final-level difference for total or free testosterone and has conflicting baseline tables. These studies do not support a single “testosterone dose.”

Sperm quality and fertility

Small studies have reported improvements in some semen measurements, but the evidence does not establish that ashwagandha increases the chance of having a baby.

In a 2013 pilot trial^[4], 46 men with infertility and low sperm concentrations received KSM-66 root extract, 225 mg three times daily, or placebo for 90 days. Average sperm concentration rose from 9.59 to 25.61 million per milliliter with the extract and from 10.24 to 13.23 with placebo. Motility—the proportion of sperm moving—rose from 18.62% to 29.19% versus 18.60% to 20.27%. The paper's often-quoted 167% increase compares the extract group with its own starting value. Its table's significance tests also concern changes from baseline. This small exploratory trial measured semen and hormones rather than pregnancies or live births.

An earlier root-powder study^[5] followed 60 infertile men whose sperm concentrations were in the normal range: smokers, men under psychological stress and men with unexplained infertility. They took 5 g daily with milk for three months. Semen measurements and hormone levels improved, and the authors reported pregnancies in partners. However, the comparison group consisted of fertile men, not randomly assigned untreated infertile men; the report also gives inconsistent pregnancy totals. It cannot tell us how many pregnancies the powder caused.

A 2025 trial^[6] tested KSM-66, 300 mg twice daily for eight weeks, in 100 otherwise healthy men seeking help for sexual dissatisfaction; 93 completed the study. Its results table found larger improvements in semen volume, total sperm per ejaculation and the proportion with normal shape. Sperm concentration and motility did not clearly improve more than placebo, despite the abstract's positive claim about concentration. Participants had to use contraception, so this was not a test of conception. Ixoreal supplied the extract, and Clinsearch provided writing and editorial support.

A separate 2026 trial^[7] in 76 men with sexual concerns reported better semen measurements with the same daily amount of KSM-66 over eight weeks. It also required contraception. Conflicting baseline and final values in its tables, along with inconsistent participant counts for some laboratory tests, leave the precise effects uncertain. These reports add evidence worth investigating, but they do not yet provide a dependable fertility treatment. The older root-powder reports also come from related research groups and cannot simply be added up as independent confirmations.

Sexual desire and erectile function

The results depend on what was measured. A 60-day trial of root powder^[8] enrolled 95 men with erectile dysfunction attributed to psychological factors; 86 completed it. At 6 g daily, the powder did not beat placebo on the International Index of Erectile Function, a questionnaire about sexual functioning.

In the 2025 KSM-66 trial above, sexual-desire scores improved more than placebo, but the total erectile-function questionnaire score, its erection domain and the number of satisfying sexual activities did not show a clear advantage. The 2026 trial reported improvements in desire and sexual-function scores, although its reporting inconsistencies still need clarification. Both trials were short and used selected men with sexual concerns. Desire, erection quality and fertility are different reasons to seek treatment, and the findings do not support one interchangeable “sexual health” promise.

Liver and thyroid safety

NCCIH reports rare cases of liver injury linked to ashwagandha supplements. Short trials cannot establish how often that happens or identify a universally safe extract.

In another eight-week study, 50 adults with subclinical hypothyroidism—an elevated thyroid-stimulating hormone (TSH) level with normal thyroxine (T4)—were assigned 600 mg a day of KSM-66 root extract or placebo; 46 finished. In the analysis that included all 50, TSH, which signals the thyroid to make hormones, fell compared with placebo, while the thyroid hormones T3 and T4 rose. The result does not establish a thyroid treatment, but it shows this extract can affect thyroid function.

What remains uncertain?

The studies leave open how often liver injury occurs, whether independent research would reproduce the KSM-66 stress results, and how the named extracts compare directly with each other.

What you may have heard on podcasts

Huberman said on 9 January 2023 that ashwagandha can be a potent cortisol reducer and may raise testosterone indirectly. He also advised against taking high doses for more than two weeks at a time, but he did not name a milligram amount.

Peter Attia said on Huberman Lab on 29 July 2024 that he uses ashwagandha with magnesium L-threonate for sleep. He also did not give an ashwagandha amount.

Neither podcast statement settles which extract or amount to choose.

Lab tests to consider when taking ashwagandha

No lab test can tell you that you are low in ashwagandha or prove that a supplement capsule is working. Thyroid and liver tests may help assess new symptoms or an existing thyroid or liver concern, when your clinician has a specific reason to order them.

Preparing for a test if you take supplements

For thyroid or liver testing, report ashwagandha use and ask the clinician whether to continue it pending the draw. There is no established ashwagandha washout period for these tests. Follow the lab’s preparation instructions, including any fasting required for liver tests^[9]. If symptoms suggest an adverse reaction, stop the supplement and seek assessment rather than waiting for a washout.

Do not wait for a self-ordered panel if yellowing of the skin or eyes or severe itching appears. Stop taking the supplement and seek prompt medical care. If you already receive thyroid treatment, your doctor can decide whether testing before and after use would be interpretable.

The bottom line

Ashwagandha has some evidence that supports modest improvements in stress and sleep, while semen and sexual-function studies have produced mixed findings. A dependable fertility or testosterone benefit remains unsettled, and results do not transfer automatically between extracts. The findings concern particular preparations and purposes.

KSM-66 is a root-only extract; Sensoril contains root and leaf; plain root powder has a different concentration. Their milligrams do not give you an interchangeable amount. Rare liver injury, thyroid concerns and limited longer-term safety information mean it is not an automatic addition for everyone.

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