Ashwagandha does appear to lower cortisol levels, and the evidence is reasonably strong. A meta-analysis of nine randomized controlled trials involving 558 people found that ashwagandha supplementation produced a statistically significant reduction in serum cortisol compared to placebo. The effect isn’t dramatic, but it’s consistent across studies, and most people in those trials also reported feeling noticeably less stressed.
How Ashwagandha Affects Cortisol
Your body produces cortisol through a chain reaction that starts in the brain. When you perceive stress, a signal travels from the hypothalamus to the pituitary gland to the adrenal glands, which then release cortisol into your bloodstream. This system, called the HPA axis, is designed to ramp up in emergencies and quiet down when the threat passes. In people dealing with chronic stress, it stays elevated.
Ashwagandha belongs to a class of herbs called adaptogens, which appear to reduce adrenal activity and help bring that stress response back toward baseline. Its active compounds are withanolides, a group of naturally occurring steroids. The two most studied are withaferin A and withanolide D. These are what supplement labels refer to when they list a “withanolide” percentage, and they’re the reason standardization matters so much when choosing a product.
What the Clinical Trials Actually Show
The pooled data from controlled trials shows that ashwagandha lowers both biological and self-reported markers of stress. Across the meta-analysis, cortisol levels dropped significantly compared to placebo, and Perceived Stress Scale scores (a standard questionnaire that measures how overwhelmed someone feels) also improved by a meaningful margin. Those two findings together are important: the cortisol drop isn’t just a lab number. It tracks with how people actually feel.
In one 60-day trial, participants taking ashwagandha saw their stress scores drop by roughly 39 to 42 percent from baseline. Doses in the broader research ranged from 125 to 600 mg daily, taken for 30 to 90 days, with both root-only and root-and-leaf formulations showing benefits.
That said, the size of the cortisol reduction varies between studies, and some trials are small. The overall body of evidence is promising but not yet definitive. This is a supplement that tilts the odds in your favor, not a guaranteed fix.
How Long Before You Notice a Difference
Some people report feeling calmer and sleeping better within about two weeks. Studies suggest that taking at least 250 mg daily for two weeks or more is enough to see an initial drop in cortisol. But the most noticeable reductions in cortisol and stress typically appear after six to eight weeks of consistent daily use. If you try it for a week and feel nothing, that’s expected. The best results in clinical trials came from people who took 500 to 600 mg per day for about six to eight weeks.
Dosage and What to Look For
The NIH notes that benefits in several studies appeared to be greater with doses of 500 to 600 mg per day than with lower doses. An international taskforce from the World Federation of Societies of Biological Psychiatry and the Canadian Network for Mood and Anxiety Treatments provisionally recommends 300 to 600 mg of root extract daily, standardized to 5% withanolides, for managing anxiety.
Standardization is the key detail most buyers overlook. Different products contain wildly different concentrations of active compounds. Some capsules deliver 2.5 mg of withanolides per dose while others deliver 21 mg, depending on the extract type and concentration. When comparing products, check the withanolide percentage or milligram count on the label, not just the total weight of the capsule. A 300 mg capsule standardized to 5% withanolides contains 15 mg of the active compounds. A 350 mg capsule with only 2.5 mg of withanolides is a very different product, even though the capsule weights look similar.
The most commonly studied branded extracts (KSM-66, Sensoril, and others) each use different parts of the plant and different extraction methods, resulting in different withanolide profiles. Any of these can work, but the dose you need depends on which one you’re taking. Matching the dose to the specific extract used in trials gives you the best shot at replicating the results.
Timing: Morning or Night
Clinical trials haven’t directly compared morning versus evening dosing for cortisol outcomes. In the studies, participants typically split their dose or took it at a consistent time each day. Since cortisol naturally peaks in the morning and tapers through the day, some people prefer taking ashwagandha in the morning to blunt that spike. Others take it at night because it can improve sleep quality, which itself helps regulate cortisol. Either approach is reasonable. If you’re splitting a 600 mg dose into two 300 mg capsules, morning and evening covers both bases.
Safety and Who Should Be Cautious
Most people tolerate ashwagandha well at standard doses for periods of up to three months, which is the longest duration most trials have tested. But there are real cautions worth knowing about.
Liver health is the most notable concern. Researchers at CU Anschutz Medical Campus have noted that most reported cases of severe liver injury occurred in people with underlying chronic liver disease, but elevated liver enzymes have also been seen in otherwise healthy people taking the supplement. If you have any liver condition, this one deserves a conversation with your doctor before you start.
Ashwagandha has also been shown to increase testosterone levels. That could be a benefit for some people, but it’s a problem for pregnant women and for anyone with hormone-sensitive conditions like prostate cancer. It may also affect thyroid hormone levels, so people with thyroid disorders should be cautious.
The supplement industry is loosely regulated, and not all products contain what they claim. One recent example: the Philippines FDA issued a public health warning against an unregistered ashwagandha product sold at 3,000 mg per capsule, a dose far beyond anything studied in clinical trials. Sticking with products that have third-party testing and reasonable dosing (under 1,250 mg per day of extract) reduces your risk of getting something unreliable or unsafe.
What Ashwagandha Won’t Do
Ashwagandha can help bring moderately elevated cortisol closer to normal in stressed but otherwise healthy people. It’s not a treatment for Cushing’s syndrome, adrenal disorders, or clinical anxiety disorders on its own. If your stress levels are high because of a situation you can change, no supplement replaces actually addressing the source. And if your cortisol is elevated due to a medical condition, the fix is medical treatment, not an herb.
For everyday stress that keeps your cortisol running higher than it should, though, ashwagandha is one of the better-studied natural options available. The cortisol reduction is modest but real, and it lines up with improvements in how people actually feel. At 500 to 600 mg of a standardized extract taken daily for at least six weeks, the evidence suggests most people will see some benefit.