Ashwagandha: Benefits, Sleep Effects & Safety
Also known as: ashwagandha benefits, ashwagandha for sleep, ksm-66, ashwagandha side effects
Ashwagandha (Withania somnifera) is an adaptogenic herb used in Ayurvedic medicine, most often taken today as a 300–600 mg standardized root-extract supplement for stress and sleep support. It has the strongest human evidence among adaptogens for modestly reducing perceived stress and cortisol over several weeks, and it's calming enough for some people that it causes daytime drowsiness, which is why it's often taken in the evening. It's generally not recommended during pregnancy, may need caution in thyroid conditions or autoimmune disease, and rare case reports have linked it to liver injury — talk to your doctor before starting, especially if you're pregnant or have a thyroid or liver condition.
Ashwagandha at a glance
| Typical dose | 300–600 mg/day (standardized extract)Often standardized to a % of withanolides (e.g. KSM-66, Sensoril). |
| Best evidence for | Stress, perceived anxiety, cortisolSeveral trials show modest reductions over 6–8 weeks. |
| Sleep effect | Calming; can cause drowsinessOften taken at night; daytime sleepiness possible in some people. |
| Thyroid | May increase thyroid hormone levelsCaution advised with hyper- or hypothyroidism — monitor with a doctor. |
Effects are generally modest and build over weeks; quality and standardization vary a lot between products.
What ashwagandha can help with
- Has the most consistent clinical trial evidence among commonly used adaptogens for reducing perceived stress and anxiety symptoms over 6–8 weeks.
- Several studies report modest reductions in cortisol, the body's main stress hormone, with regular use.
- Often used to support sleep quality and sleep onset, given its calming effect for many users.
- Some research suggests possible benefits for exercise performance, strength, and recovery, though this evidence is less robust than the stress data.
- Preliminary studies have explored effects on mood and cognitive function, but this research base is smaller and less conclusive.
How and when to take it
- Typical doses are 300–600 mg per day of a standardized root extract (often labeled by withanolide content), taken once daily or split into two doses.
- Many people take it in the evening because it tends to be calming and can cause drowsiness — a useful timing choice if you're using it partly for sleep.
- If you notice daytime grogginess, try shifting the dose to night only or lowering it, rather than taking it before activities requiring alertness.
- Give it 6–8 weeks of consistent use before judging its effect on stress or sleep, since benefits build gradually in most trials.
- Take with food if it causes mild stomach upset.
Cautions and interactions
- Ashwagandha is generally not recommended during pregnancy, as it may stimulate uterine activity, and safety data in pregnancy are insufficient — avoid it if you're pregnant or trying to conceive.
- It can affect thyroid hormone levels (sometimes raising them), so people with hyperthyroidism, hypothyroidism, or Hashimoto's should use it only under medical supervision and with monitoring.
- May stimulate the immune system, which is a caution for people with autoimmune conditions like rheumatoid arthritis or lupus — check with a doctor first.
- Rare case reports have linked ashwagandha to liver injury; stop use and seek medical care if you notice yellowing skin or eyes, dark urine, or unusual fatigue.
- Can cause drowsiness — use caution combining it with sedatives or alcohol, or before driving, until you know how it affects you.
- May interact with thyroid medication, immunosuppressants, and sedatives — review your medication list with a clinician before starting.
Is Ashwagandha right for you?
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Frequently asked questions
Does ashwagandha make you sleepy?
It can. Ashwagandha has a calming, mildly sedating effect for many people, which is part of why it's popular for stress and sleep support and often taken in the evening. Some people also notice daytime drowsiness, especially at higher doses — if that happens, try taking it only at night or lowering the dose, and be cautious combining it with alcohol or other sedatives until you know how it affects you.
Does ashwagandha actually lower cortisol?
Several randomized trials support modest reductions in perceived stress and cortisol with regular ashwagandha use, typically at 300–600 mg/day over 6–8 weeks — it has some of the strongest human evidence among adaptogens. The effects are real but generally modest, and ashwagandha works best alongside, not instead of, good sleep, exercise, and stress management.
Is ashwagandha safe for the thyroid?
Ashwagandha can raise thyroid hormone levels in some people, which is a meaningful caution if you have hyperthyroidism, hypothyroidism, or an autoimmune thyroid condition like Hashimoto's. It isn't automatically unsafe, but anyone with a thyroid condition should use it only with medical supervision and periodic monitoring rather than self-managing.
Can ashwagandha cause liver damage?
Rare case reports have linked ashwagandha use to liver injury, though this appears uncommon relative to how widely it's used. If you notice symptoms like yellowing of the skin or eyes, dark urine, unusual fatigue, or abdominal pain while taking it, stop and seek medical care. People with existing liver disease should talk to a doctor before starting ashwagandha.
Can you take ashwagandha while pregnant?
No — ashwagandha is generally not recommended during pregnancy because it may stimulate uterine activity and safety data in pregnant people are insufficient. If you're pregnant, trying to conceive, or breastfeeding, avoid it and talk to your OB about safer options for stress and sleep support.
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Medically reviewed by Antonieta Rueda, MD and Kyle R. Toth, MD · Last reviewed July 6, 2026
This article is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Dietary supplements are not regulated like medications, quality varies between products, and they can interact with prescription drugs and existing conditions. Talk to your doctor or pharmacist before starting any supplement, especially if you are pregnant, nursing, have a medical condition, or take other medications.