What dose of ashwagandha was used in studies?

Trials commonly used standardized root extracts at 240 to 600 mg a day for about 8 weeks. A dose-response analysis found the stress benefit around 300 to 600 mg a day. These are study doses, not personal recommendations.

How long does ashwagandha take to work?

Most trials measured results after about 6 to 12 weeks. There is little good evidence on effects within days.

It appears well tolerated for up to about 3 months in trials, but long-term safety is unknown. Case series describe liver injury with jaundice, and deaths in people with existing liver disease. Avoid it in pregnancy, and talk to a clinician if you have liver or thyroid conditions or take medicines.

Is ashwagandha banned anywhere?

According to the NIH Office of Dietary Supplements, Denmark banned its use in 2023, and France's food safety agency recommended against it in 2024 for some groups, including pregnant and breastfeeding women and people with endocrine disorders.

Does ashwagandha help sleep?

A few trials suggest better sleep quality and shorter time to fall asleep, mostly in people with insomnia. Evidence is limited and comes from a small number of studies.

Should you take ashwagandha every day?

Andrew Huberman says he uses it only in unusually stressful periods rather than year-round. Trials lasted about 2 to 3 months, so long-term daily use has not been well studied.

Does Ashwagandha Lower Cortisol and Stress? Dose, Evidence and Safety

Q: Does ashwagandha lower cortisol?

In small placebo-controlled trials, yes. A 60-day trial in 64 stressed adults and another in 60 adults both found larger falls in cortisol than with placebo, and a 2024 meta-analysis of 9 trials found lower serum cortisol overall. The trials were small and often industry-linked.

Small randomized trials suggest a standardized ashwagandha root extract, at about 240 to 600 mg a day for roughly two months, can lower self-reported stress and cortisol compared with placebo. Two meta-analyses, from 2022 and 2024, support a benefit, but the first rates the evidence as low certainty. It is not risk-free: case series describe liver injury, and some countries now restrict it.

This page is general information, not medical advice. Supplements are not evaluated by the FDA for effectiveness. Check with a clinician before use, especially if you are pregnant, take medicines, or have a liver or thyroid condition.

What the trials found

Study	Who	Dose	Main result
Chandrasekhar et al., 2012	64 adults with chronic stress	300 mg root extract twice daily, 60 days	Lower scores on all stress scales and lower serum cortisol vs placebo
Lopresti et al., 2019	60 stressed but healthy adults	240 mg standardized extract once daily, 60 days	Lower anxiety (HAM-A) and morning cortisol; broader stress questionnaire only near-significant
Meta-analysis, 2022	12 RCTs, 1,002 participants	Various	Reduced anxiety and stress; stress benefit at 300–600 mg/day; low certainty
Meta-analysis, 2024	9 RCTs, 558 participants	Various	Lower perceived stress, anxiety and serum cortisol vs placebo

In the 2012 trial, adverse effects were mild and comparable between groups. The 2019 trial reported no adverse events, and noted that testosterone rose in men over time but not significantly more than with placebo. Its authors suggest the herb may work through the stress-hormone (HPA) axis and called for larger, more diverse trials.

The 2022 meta-analysis found high variation between studies and concluded that “the certainty of the evidence was low for both outcomes.” In the 2024 analysis, 4 of the 9 trials reported mild to moderate adverse events, and the authors said more information is needed on long-term safety.

How big is the effect?

On the Perceived Stress Scale, the pooled score was about 4.7 points lower with ashwagandha than with placebo, and anxiety scores were about 2.2 points lower on the Hamilton scale. Questionnaire scores like these are vulnerable to expectation effects if blinding is imperfect.

Why the evidence is rated low

Small trials: the 2024 meta-analysis pooled only 558 people across 9 trials.
Short follow-up: the trials above lasted 60 days, and tolerability data cover only about 3 months.
Product-specific: most used branded extracts, often supplied or funded by the manufacturer.
Different extracts: products vary in plant part (root or root plus leaf) and withanolide content, so results from one product may not transfer to another. The NIH Office of Dietary Supplements lists trial extracts standardized to different withanolide levels.

What Huberman says

On the Huberman Lab episode on stress and anxiety, Andrew Huberman describes ashwagandha as lowering anxiety and cortisol. Citing Examine.com, he reports reductions in cortisol of 14.5 to 27.9 percent across six studies in stressed but otherwise healthy people. He says he would only use it when he felt he wasn’t managing short- and medium-term stress well: “I’m not going to take Ashwagandha year round.” That cautious, short-term use matches the length of the trials.

Doses used in studies

Detail	What the trials used
Form	Standardized root extracts (some root plus leaf)
Dose	240 mg once daily up to 300 mg twice daily (600 mg/day)
Duration	About 6 to 12 weeks
Timing	Not established; many trials used once or twice daily dosing

These figures describe what the Chandrasekhar and Lopresti trials and the dose-response analysis used, not personal recommendations.

Sleep

According to the NIH fact sheet, a small number of studies suggest ashwagandha may improve sleep quality, total sleep time and time to fall asleep, with larger benefits in people with insomnia. In one 6-week trial of 150 adults with self-reported sleep problems, sleep quality improved in 72% of the ashwagandha group versus 29% with placebo. The research base is still limited.

Safety

The NIH Office of Dietary Supplements says ashwagandha appears well tolerated for up to about 3 months, but its long-term safety is not known.

Liver injury: a 2020 case series described five people who developed jaundice, itching and nausea after a latency of 2 to 12 weeks. None developed liver failure, and liver tests returned to normal within 1 to 5 months in four. The authors concluded: “These cases illustrate the hepatotoxic potential of ashwagandha.”
Pre-existing liver disease: an Indian multicenter series reported 8 single-ingredient cases. Five already had chronic liver disease. Three of them arrived with acute-on-chronic liver failure, and all three died. Chemical analysis found no contamination.
Thyroid and medicines: the NIH fact sheet notes possible effects on thyroid function and possible interactions with thyroid hormone, diabetes, blood pressure, immunosuppressant and sedative medicines.
Pregnancy: some experts advise against it during pregnancy because of reports of possible miscarriage risk.

Stop and seek care if you notice yellowing skin or eyes, dark urine or persistent itching.

Regulatory cautions

The NIH fact sheet reports that Denmark banned the use of ashwagandha in 2023 after a 2020 risk assessment. In 2024, France’s food safety agency ANSES recommended against it for certain groups, including pregnant and breastfeeding women and people with endocrine disorders.

How it compares with other options

Option	Evidence for everyday stress	Main cautions
Ashwagandha	Several small RCTs; low-certainty meta-analysis	Rare liver injury; thyroid and drug interactions; pregnancy
L-theanine	Small trials, mostly acute stress	Generally well tolerated in studies
Breathing, sleep, exercise	Covered on the short-term vs chronic stress page	No supplement risks

Huberman frames supplements as a backup when behavioral tools are not enough. Those tools include exhale-focused breathing such as the physiological sigh. For general advice on choosing tested products, see the evidence-based supplements guide.