Taking ashwagandha: dosage, extracts, timing and risks

How much ashwagandha has been studied for stress or sleep problems, and does the time of day you take it matter? Studies often used standardized extracts at 300 to 600 mg a day. How the results turn out depends on the extract, the complaints being studied and the people taking part. No general dosing recommendation follows from this. Long-term safety and the most favorable time to take it are also not yet sufficiently understood.

How much, in what form and at what time?

Studies on stress, sleep problems and hormonal changes have tested a range of products and dosing schedules. A common choice was 300 to 600 mg a day of a standardized root extract. Standardized here means the extract contains a fixed proportion of certain plant compounds. The amounts in the table describe how the products were used in studies; they are not a personal dosing recommendation.

Outcome studied	Extract	Daily dose	Timing	Study length
Stress and cortisol	KSM-66	300 to 600 mg (2022 meta-analysis)	In the morning, or split between morning and evening	8 weeks
Sleep quality	Root extract	600 mg, split into 300 mg twice a day (2019 randomized controlled trial)	Evening	10 weeks
Testosterone in men	KSM-66	600 mg	Once a day or split	8 weeks

The details of the sleep study contradict each other on timing: 300 mg twice a day cannot clearly be reconciled with taking it only in the evening. The exact schedule therefore remains unclear.

Form

KSM-66 and Sensoril, the two most frequently studied extracts, contain different amounts and mixtures of withanolides, which are biologically active plant compounds. The effects that have been studied also differ between the extracts. Ordinary ashwagandha powders and non-standardized capsules have a different composition, so study results cannot simply be transferred to them.

Dose

There is no reliable answer to the question of how much ashwagandha is too much. Safety studies in healthy adults tested 125 to 600 mg a day for up to 180 days. For higher amounts, solid long-term data in particular are lacking (2026 systematic review).

Most sleep studies used 600 mg a day (2021 meta-analysis). Higher doses have also been tested for safety, but they showed no additional benefit on stress-related outcomes. Other uses might call for other amounts. So far, no established dosing recommendation follows from this.

A common piece of advice is to start with a lower dose and adjust it depending on effect and tolerability. Even with this approach, it remains open which maximum dose would be safe in general. Individual risks need to be checked regardless.

Timing

Ashwagandha is taken in the morning, in the evening or split across both. People sometimes go by the daily curve of the stress hormone cortisol and by which complaints are most prominent. That does not establish a single best time.

Splitting it into 300 mg in the morning and 300 mg before bed is said to influence the cortisol curve in both the morning and the evening. Whether this split offers advantages over other timings is an open question.
Absorption with and without food is described as broadly comparable. Some users report that taking it with a meal reduces gastrointestinal discomfort.

Combinations

Ashwagandha is often combined with other so-called adaptogens such as rhodiola, also known as roseroot, or holy basil. The term adaptogens refers to plant substances credited with helping the body adapt to stress. There is no clinical evidence that these combinations work better than ashwagandha alone.

Taking it together with magnesium for sleep problems or stress is also common. The fact that a combination is widely used, however, does not show that it is free of interactions.

Combining it with sedating medications or other GABAergic substances should only be done under medical supervision. GABAergic means that a substance acts on the inhibitory signaling system of the messenger GABA. The calming, dampening effects can add up. With thyroid medication, close monitoring of thyroid function is important, because ashwagandha can raise thyroid hormone levels in some people.

What ashwagandha is and how standardized extracts differ

Ashwagandha has been used in Ayurvedic medicine for centuries. One of the parts used is the root of the plant Withania somnifera. Much of the bodily effect that has been studied is attributed to the withanolides it contains. Their concentration and composition vary considerably depending on extraction and processing. Different ashwagandha products can therefore act differently in the body.

Clinical research frequently studies two manufacturer-specific extracts:

KSM-66 is a full-spectrum extract made only from the root, standardized to at least 5% withanolides. A water-based extraction process is said to preserve the natural ratio of compounds found in the whole root.
Sensoril is made from roots and leaves and standardized to a higher withanolide concentration, typically 10%. The withanolide withaferin A is mentioned in particular.
KSM-66 has mainly been studied for stress reduction, endurance, testosterone in men and cognitive performance.
Sensoril comes up more often in connection with studies on metabolic markers and body composition.

The withanolide makeup may influence which biological signaling pathways an extract acts on. For the full-spectrum profile of KSM-66, broader effects on stress adaptation are being discussed. Sensoril’s higher withaferin A content is credited with stronger effects on inflammatory processes and metabolic signals. These ideas about possible mechanisms do not show that either extract is clinically superior.

For powders or capsules with no information on standardization and extraction method, it remains unclear how comparable they are to the products that were studied. The same results therefore cannot be assumed. Depending on growing conditions, harvest time and processing, withanolide content can range from less than 1% to over 10%.

What clinical studies show on stress, cortisol and sleep

For effects on stress and cortisol, there is more clinical evidence for ashwagandha than for many other herbal adaptogens. The results differ, however, depending on the population and the outcome measured. A 2019 randomized controlled trial with KSM-66 in adults with chronic stress reported statistically significant decreases in perceived stress and in morning cortisol levels compared with placebo. On average, cortisol fell by about 25% from baseline. That figure describes the change since the start of the study, not the difference from the placebo group. The effect was described as clearest in people whose cortisol was elevated at the outset and weaker in those with normal starting values.

For sleep, the results are more mixed. A 2020 study with ashwagandha root extract in adults with insomnia reported better sleep quality, faster sleep onset and longer total sleep time. The effect size was moderate, and not every participant benefited. One proposed explanation is a drop in nighttime cortisol and a change in how the HPA axis is regulated. This hormonal stress axis links the hypothalamus, the pituitary gland and the adrenal glands. Through it, ashwagandha might indirectly influence sleep architecture, meaning the sequence of sleep stages. Whether this mechanism explains the improvements that were observed has not been shown. A direct calming effect is not ruled out either.

For anxiety, too, there are signs of a benefit, but with limited generalizability. A meta-analysis of five randomized controlled trials found statistically significantly lower anxiety scores than with placebo. The studies were small, however, used different doses and often enrolled people whose anxiety fell below the threshold of a diagnosed anxiety disorder. One proposed explanation is an effect on NMDA receptors and on the GABA system, both of which are involved in signaling between nerve cells. Whether ashwagandha effectively treats anxiety disorders cannot be inferred from these mechanisms.

There are fewer data on cognitive performance. A few small studies with KSM-66, or with a combination of magnesium L-threonate and ashwagandha, reported improvements in memory and reaction time. Confirmation in larger, well-controlled studies is still pending. The changes may stem mainly from lower stress rather than from a direct boost to brain performance. To put the studies as a whole in context, it also matters that most were industry-funded, lasted only 8 to 12 weeks and enrolled relatively healthy adults.

How ashwagandha might influence the HPA axis and the cortisol rhythm

The hypothalamic-pituitary-adrenal axis, or HPA axis for short, controls a large part of the body’s stress response. Chronic stress can alter how it is regulated. Changes that have been described include elevated morning cortisol, a blunted additional rise in cortisol after waking and a disrupted daily rhythm. Researchers are investigating whether withanolides from ashwagandha can dampen excessive activation of this axis through several signaling pathways.

One possible target is the GABA-A receptors in the brain. Through them, withanolides might strengthen inhibitory signals and lower excitatory activity. Benzodiazepines also act on this receptor system, but they bind differently and act much more strongly. The weaker binding of ashwagandha compounds is not enough to rule out a risk of dependence.

Another possible target is the sensitivity of glucocorticoid receptors, which helps determine how cells respond to cortisol. With chronic activation of the HPA axis, these receptors can become less sensitive: cortisol levels are then high while cells respond more weakly to the hormone. Ashwagandha might help restore this sensitivity and so allow an appropriate stress response without excess cortisol production. This explanation of a possible mechanism has not been shown to hold as an effect in everyone who takes it.

Researchers are also looking at the ratio of cortisol to DHEA-S. DHEA-S is an androgen made mostly in the adrenal glands. That places it among the male sex hormones, but it is present in people of all sexes. DHEA-S counteracts some of cortisol’s tissue-breakdown effects. Studies report that ashwagandha can lower the cortisol-to-DHEA-S ratio. A lower ratio is associated with better stress coping and recovery (2019 randomized controlled trial).

Cortisol follows a daily rhythm. It typically peaks within 30 minutes of waking and then falls over the course of the day to its nighttime low. Chronic stress can flatten this curve, and high levels in the evening can go along with sleep problems. Possible effects of ashwagandha that have been described include softening excessive morning peaks in stressed people and a stronger natural drop in the evening. This does not yet tell us which time of day would suit a particular person.

Who might be most likely to benefit, and when caution is needed

The effects described are reported most clearly in people with elevated baseline cortisol, chronic stress, or anxiety below the threshold of a diagnosed anxiety disorder. With normal cortisol levels and without marked stress, the benefit is likely to be smaller. The assumption behind this is that ashwagandha mainly acts on disturbed stress regulation and does little to improve regulation that already works well. It does not follow, however, that it merely makes up for a deficit or has no pharmacological effect.

In men with low testosterone, moderate improvements are conceivable, particularly when stress contributes to the low levels. This cannot be applied to primary hypogonadism, in which the testes produce too little sex hormone. For a 2019 study in overweight men, cited in connection with KSM-66, a 15% rise in testosterone is described. It occurred alongside weight loss and improved body composition, so how much of it was due to the extract alone is hard to judge. Women with polycystic ovary syndrome (PCOS) or elevated androgen levels should be cautious: a rise in testosterone and DHEA-S could make symptoms worse.

Older adults might benefit from effects on muscle strength and recovery. At the same time, possible interactions with medications matter, especially drugs that affect thyroid function, blood pressure or blood sugar. Ashwagandha can lower blood sugar and blood pressure, which may mean a doctor needs to adjust diabetes or blood pressure medication.

Particular restrictions apply to certain groups:

People who are pregnant or breastfeeding should avoid ashwagandha. Adequate safety data are lacking, and some animal studies describe possible effects on fetal development (2025 systematic review).
Caution is needed with autoimmune thyroid disease, especially Hashimoto’s thyroiditis. Ashwagandha can increase thyroid hormone production. Whether it could also intensify autoimmune activity is under discussion.
People with Graves’ disease or an overactive thyroid should not take ashwagandha.
With longer use, liver function tests are advisable. Case reports describe elevated liver enzymes and liver damage in connection with ashwagandha.
With medications broken down by the enzyme CYP3A4, drug levels could change. Medical supervision is therefore required.

Cycling, tolerance and the question of breaks

Clinical studies have not settled whether regular breaks from taking it make sense. Most studies last 8 to 12 weeks. They do not capture what happens with longer continuous use. The idea of breaks rests on the concern that the body gets used to the influence on the HPA axis and the effect wears off. This assumption is plausible but unproven.

Some practitioners recommend 2 weeks on followed by 1 week off, or 3 months on followed by 1 month off. Breaks are meant to give the HPA axis time to readjust and to keep the targeted receptors from becoming less sensitive or fewer in number. Direct evidence for this kind of tolerance with continuous use is lacking. Conversely, some users report a lasting benefit over six months or more without breaks. Such reports can establish neither long-term efficacy nor safety.

If the perceived effect fades after several months, a break of two to four weeks is suggested to gauge whether there is still a benefit. A return of the effect after the break would be consistent with tolerance but would not prove it. If the effect does not come back, possible explanations include placebo effects or a change in stress levels in the meantime.

A break can also be a prompt to check whether taking it still makes sense. Ashwagandha is not a permanent solution for chronic stress; its causes still matter. If stress levels have not changed after three months, factors such as lack of sleep, poor nutrition or unresolved psychological strain may be playing a role. The lack of an effect alone, however, cannot diagnose the cause.

Side effects, interactions and warning signs

In most clinical studies, ashwagandha was well tolerated. The following side effects have nonetheless been described:

The most commonly reported are gastrointestinal complaints such as nausea, diarrhea and upset stomach, particularly at higher doses or when taken on an empty stomach.
Drowsiness can occur at any time of day in sensitive people and can be disruptive during the day. Whether it is more common with morning or evening use is not clearly stated.
Changes in thyroid function can be more serious. Ashwagandha can raise levels of the thyroid hormones T3 and T4. In subclinical hypothyroidism this is being studied as a possible benefit, but no general treatment recommendation follows from it. With normal or already elevated thyroid function, a further increase can be a problem.
Elevated liver enzymes have been reported in a small number of cases. In some of the people affected, clinically apparent liver injury developed.

If you take thyroid medication at the same time, TSH as well as free T3 and free T4 should be checked regularly, since the dose may need adjusting. TSH is the control hormone that prompts the thyroid to produce its hormones. Free T3 and T4 are the portions of the hormones not bound to transport proteins. People with an overactive thyroid or Graves’ disease should not take ashwagandha.

With longer use, liver function also deserves attention, particularly at more than 600 mg a day or when other supplements or medications that strain the liver are taken at the same time. Whether the 2025 study reference cited for this supports these specific risks remains unclear because its bibliographic entry is incomplete.

Because of its mild immune-stimulating effects, ashwagandha could interact with immunosuppressants, the medications that suppress the immune system. Anyone taking them for an autoimmune disease or after a transplant should discuss its use with a doctor beforehand. Ashwagandha can also intensify the effects of sedatives, benzodiazepines and other substances that depress the central nervous system.

Measuring cortisol to judge a possible effect

Changes in symptoms and changes in the body do not always line up. Perceived stress and HPA axis function, for example, can move in different directions. For a single cortisol measurement, the morning within 30 minutes of waking is often chosen. A saliva test with four time points, on waking, at midday, in the evening and before bed, can map the daily curve.

DHEA-S can add information. A high cortisol-to-DHEA-S ratio is associated with chronic stress. In clinical studies, a decrease in this ratio was described with ashwagandha (2019 study). Neither a single value nor the ratio, however, diagnoses chronic stress or proves that the supplement is beneficial.

Other tests mentioned are TSH, free T3 and free T4 before starting and after 3 months, as well as hs-CRP. hs-CRP is a high-sensitivity inflammation marker that can point to low-grade inflammatory processes. Comparing values before starting and after 3 months can document changes. On its own, though, the comparison shows neither with certainty whether ashwagandha caused them nor which dose would be appropriate. Which tests make sense in an individual case depends on the clinical context.

Frequently asked questions

How do the ashwagandha extracts KSM-66 and Sensoril differ?

KSM-66 is a full-spectrum extract made only from the root. It is produced with a water-based process and standardized to at least 5% withanolides. It has mainly been studied for stress, testosterone in men and cognitive performance, often at 300 to 600 mg a day.

Sensoril is made from roots and leaves, standardized to 10% withanolides and described as having a higher concentration of withaferin A. It comes up more often in connection with studies on metabolic markers and body composition. Because their composition differs, the extracts are not simply interchangeable. The fact that they act on different signaling pathways does not, by itself, show that they have different clinical benefits.

Should ashwagandha for stress be taken in the morning or the evening?

No single best time has been established. People go by their cortisol curve and their main complaints. Based on the proposed mechanisms, taking it in the morning seems plausible when high cortisol after waking, morning anxiety or daytime stress are the main issue. Taking it in the evening is considered when it is hard to wind down, when nighttime cortisol is elevated or when sleep is poor.

Splitting it into 300 mg in the morning and 300 mg before bed is said to influence the cortisol curve at both times of day. This matches a dosing schedule often described in stress-reduction studies. Its frequent use does not show that it beats other timings.

Is long-term daily use without breaks safe?

The safety of long-term continuous use has not been adequately studied. Most clinical trials last only 8 to 12 weeks. Case reports with longer-term use describe elevated liver enzymes and a reversible suppression of adrenal function, meaning an impairment that resolved again.

A common suggestion is to take a 1-month break after 3 months of use. There is no clinical evidence that such a break in some sense resets the HPA axis. It does, however, offer a chance to judge whether the benefit continues. With longer use, checks of thyroid and liver function are advisable.

What are the most common side effects, and how can they be kept down?

The most commonly described are nausea, diarrhea and upset stomach, particularly at higher doses or when taken on an empty stomach. Taking it with a meal can reduce these complaints. Drowsiness is also possible, including with evening use. More serious are changes in thyroid function, which can go unnoticed without testing.

A cautious approach that has been suggested is to start with a lower dose, for example 300 mg, and adjust it depending on effect and tolerability. Even this amount is not suitable for everyone and is not a risk-free starting dose.

How can you tell whether ashwagandha is working?

Changes in symptoms are an important but incomplete yardstick. Measuring morning cortisol and DHEA-S before starting and after 8 to 12 weeks can provide objective values for comparison. Falling cortisol and a change in the cortisol-to-DHEA-S ratio can document bodily changes that fit the effects under discussion. On their own, they prove neither a health benefit nor that ashwagandha caused the changes.

If subjective stress improves while cortisol stays the same, possible explanations include placebo effects or lifestyle changes. Here too, the cause remains unclear. Wearables that track sleep quality and heart rate variability can add further clues. Heart rate variability refers to the variation in timing between heartbeats. Such data do not replace a clinical assessment.

Can ashwagandha be combined with other supplements or medications?

Ashwagandha is taken together with magnesium and other common supplements, among others. That does not mean every combination is safe across the board.

Ashwagandha should not be combined with benzodiazepines, barbiturates, alcohol or other GABAergic substances without medical supervision, because the dampening effects can add up. With thyroid medication, TSH as well as free T3 and T4 need close monitoring: ashwagandha can increase thyroid hormone production and so change how much medication is needed. With immunosuppressants and drugs broken down by CYP3A4, use should also be discussed with a doctor beforehand.

Does the form, powder or extract, matter for how well it works?

The composition helps determine whether study results can be applied to a product. Powders or capsules without defined standardization can have withanolide concentrations from less than 1% to over 10%. That makes the amount actually taken in, and the effect to expect, hard to predict.

Clinical studies mostly use standardized extracts such as KSM-66 or Sensoril rather than unprocessed powders. KSM-66 contains only root extract, while Sensoril also includes leaf material. Information on the specific extract and its withanolide content helps judge whether a product is comparable to one that has been studied. A matching standardization does not, however, guarantee that the study result will repeat itself in an individual person. With non-standardized products, a consistent effect is especially hard to gauge.

Which biomarkers matter before and after starting?

Possible measurements mentioned are morning serum cortisol and DHEA-S, to put HPA axis and adrenal function in context. TSH as well as free T3 and T4 serve to pick up possible changes in thyroid hormones. hs-CRP is a marker of inflammatory processes in the body, which ashwagandha might influence. All values have to be interpreted in the relevant clinical context. On their own, they reliably show neither how much functional reserve the adrenal glands have nor what individual benefit taking it brings.

Repeat measurements of cortisol and DHEA-S after 8 to 12 weeks show whether their ratio has changed. This ratio is discussed as a complementary and possibly more sensitive indicator of stress regulation than cortisol alone. A change, however, does not confirm that the body’s biological stress responses as a whole have normalized. With longer-term use of higher doses, checks of the liver enzymes ALT and AST are also recommended.

References

The first entry deals with omega-3 fatty acids and provides no direct evidence on ashwagandha. In Mallinson et al., the title is incomplete, so the specific claim of the paper cannot be judged from it. In addition, based on the bibliographic details, the 2020 sleep study described in the text cannot be equated with the listed 2019 paper by Langade et al.

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Lopresti AL, Smith SJ, Malvi H, Kodgule R (2019). An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study. Medicine, 98(37), e17186. https://doi.org/10.1097/MD.0000000000017186. PubMed
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