How Long Does Ashwagandha Take to Work? What the Trials Measured

How long does ashwagandha take to work? Plan on six to eight weeks. In the trials, the clear differences from placebo in stress, anxiety and cortisol appeared at around eight weeks, not at four. Sleep benefits were also stronger after at least eight weeks. Ashwagandha has not been shown to work within days, so judge it after two months of steady use, not two weeks.

Most pages answering this question offer a week-by-week timeline of what you will “start to feel”. The trials do not support that level of detail. What they do show is clearer, and more useful: when the measurable effects appeared, at what dose, and how long people have safely taken it.

The short version

• Stress and anxiety: trials lasted six to eight weeks. In one trial that checked at both four and eight weeks, the gap from placebo was small at four weeks and clear at eight.
• Cortisol: the main trials measured falls of 23% to 28% at around 60 days.
• Sleep: a review of five trials found the benefit was greater when ashwagandha was taken for at least eight weeks.
• Dose matters: 500 mg to 600 mg a day of standardised extract tended to work better than lower doses.
• Safety window: it appears well tolerated for up to about three months. Longer-term safety is not known.

How this article was done

I have not taken ashwagandha, and there is no test panel, because there was none. I read the main randomised trials, including the week-by-week results where they were published, and the US National Institutes of Health fact sheet on ashwagandha, noting who funded each study. This is general information, not medical advice, and it follows my methodology.

What the trials measured, and when

Trial	Who	Dose	Length	What changed vs placebo
Chandrasekhar, 2012	64 adults with chronic stress	300 mg twice a day	60 days	Cortisol −27.9% vs −7.9%; all stress scales improved
Salve, 2019	60 stressed adults	250 mg or 600 mg a day	8 weeks	Stress and cortisol lower at 8 weeks; anxiety lower at 600 mg
Lopresti, 2019	60 stressed adults	240 mg a day	60 days	Anxiety lower; morning cortisol −23%

The four-week checkpoint

The most useful trial for the “how long” question is the 2019 study by Salve and colleagues in Cureus, because it measured perceived stress at four weeks as well as at eight. At four weeks, the average stress score was 18.8 in both ashwagandha groups and 19.9 on placebo: a small gap. By eight weeks it was 15.0 on 250 mg and 14.2 on 600 mg, against 16.6 on placebo, and those differences were statistically significant. Blood cortisol followed the same pattern, with the largest drop at eight weeks on 600 mg.

In other words, the measurable effect built up over the second month. That is the clearest evidence there is on timing, and it is why judging ashwagandha after a week or two is premature.

The 60-day trials

Two other well-known trials ran for 60 days. In the 2012 trial by Chandrasekhar and colleagues, 64 adults with chronic stress took 300 mg of a root extract twice a day; serum cortisol fell by 27.9%, against 7.9% on placebo, and every stress questionnaire improved more than on placebo. In a 2019 trial in Medicine by Lopresti and colleagues, 60 stressed adults took 240 mg a day of a different extract; anxiety scores fell further than on placebo and morning cortisol dropped by 23%.

The NIH’s summary of seven trials, covering 491 adults in India, found reductions in stress, anxiety, sleeplessness and cortisol over six to eight weeks, with benefits that “appeared to be greater with doses of 500 to 600 mg/day than with lower doses.”

One caveat applies to all of this: the trials are small, mostly from India, and several were funded or supplied by the companies that make the extracts tested. The Salve trial used an extract supplied by its manufacturer, and the Lopresti trial was funded by the maker of its extract. The results are consistent, but they are not independent.

Sleep

A 2021 meta-analysis of five trials in 372 adults, summarised by the NIH, found a small but significant improvement in sleep. The benefit was more pronounced at 600 mg a day and when ashwagandha was taken for at least eight weeks.

A realistic timeline

• The first days: no trial has shown a meaningful effect from a single dose. Any change this early is hard to tell apart from expectation.
• Around four weeks: in the one trial that checked, the difference from placebo was small. A slight improvement is plausible; a large one is not what the data shows.
• Six to eight weeks: this is where the trials measured clear effects on stress, anxiety and cortisol, and where sleep benefits were strongest.
• Around three months: the limit of the safety data. If you want to continue beyond that, talk to a doctor.

A sensible approach is to take a consistent dose for eight weeks, note how you feel before you start and at the end, and stop if nothing has changed.

What makes it work sooner or not at all

• The dose. 500 mg to 600 mg a day of extract was generally more effective than lower doses. There is no evidence that going higher speeds things up.
• The product. The trials used extracts standardised for withanolides, the plant’s active compounds. Raw root powder with no stated withanolide content cannot be compared with what was tested. I explain how to check this in my guide to the best supplement to lower cortisol.
• Consistency. The trials gave it every day, often split into two doses. Missing doses makes it harder to judge.
• The kind of problem. The trials recruited people with everyday high stress. An anxiety disorder, depression or a sleep disorder needs proper assessment, not a longer course of a supplement.

Safety: how long you can take it

The NIH fact sheet says ashwagandha “appears to be well tolerated for up to about 3 months of use”, and that its long-term safety is not known. Common side effects are mild: stomach upset, loose stools, nausea and drowsiness. There are rare reports of liver injury, including five cases in people taking 450 mg to 1,350 mg a day for between one week and four months, and reports of effects on thyroid hormones (see ashwagandha and thyroid).

Avoid ashwagandha if you are pregnant or breastfeeding, and talk to a doctor first if you have a thyroid, liver or autoimmune condition, have hormone-sensitive prostate cancer, or take medicines for diabetes, blood pressure, thyroid, seizures or immunity, or sedatives. If you notice yellowing of the skin or eyes, dark urine or persistent abdominal pain, stop and seek medical advice.

If you are comparing options, the evidence on magnesium is in magnesium for anxiety, and L-theanine, which acts within about an hour, is covered in L-theanine side effects.

Comparing options? All seven of the main stress supplements are ranked on their trial evidence in best supplements for stress.

Thinking of pairing ashwagandha with magnesium? No interaction is known, but the cautions of each still apply: see magnesium and ashwagandha.

Choosing a product? Six popular ashwagandha supplements are compared on extract, dose against the trials and cost per day in the best ashwagandha supplement.

Common questions

How long does ashwagandha take to work?

Plan on six to eight weeks. The trials measured clear effects on stress, anxiety and cortisol at around eight weeks, with only small differences from placebo at four weeks.

Can you feel ashwagandha right away?

No trial has shown a meaningful effect from a single dose. It is studied as a daily supplement whose effects build up over weeks.

How long does ashwagandha take to work for sleep?

A review of five trials found the sleep benefit was greater when it was taken for at least eight weeks, at around 600 mg a day.

How long does ashwagandha take to lower cortisol?

The main trials measured cortisol falls of about 23% to 28% after roughly 60 days. In one trial, the drop at four weeks was much smaller than at eight.

How long can you safely take ashwagandha?

According to the NIH, it appears well tolerated for up to about three months. Safety over longer periods is not known, so talk to a doctor before continuing beyond that.

Should I take ashwagandha in the morning or at night?

The trials did not compare timing, and many split the dose into morning and evening. If it makes you drowsy, taking it in the evening is reasonable.

Sources

• NIH Office of Dietary Supplements — Ashwagandha: Is it helpful for stress, anxiety, or sleep? — trial summaries, the three-month safety window, liver and thyroid reports.
• Salve J et al. Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults. Cureus. 2019 — the four-week and eight-week results.
• Chandrasekhar K et al. A Prospective, Randomized Double-Blind, Placebo-Controlled Study of Safety and Efficacy of a High-Concentration Full-Spectrum Extract of Ashwagandha Root in Reducing Stress and Anxiety in Adults. Indian Journal of Psychological Medicine. 2012 — the 60-day cortisol trial.
• Lopresti AL et al. An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract. Medicine. 2019 — the 240 mg trial and its funding.
• National Center for Complementary and Integrative Health — Ashwagandha — safety cautions and medicine interactions.