Ashwagandha side effects: what you should know before you start
Ashwagandha has become one of the most popular supplements for stress. But what does the research say about its safety? Here is an honest review – without scaremongering and without glossing over anything.
Is ashwagandha safe to take?
For most healthy adults: yes. In clinical studies using 240 to 600 mg of standardised root extract per day, for up to 12 weeks, side effects have been few and mild. The proportion of participants who dropped out due to problems was roughly the same as in the placebo groups.
Two things are worth knowing. Long-term data spanning several years is lacking. And quality varies enormously between products – the studies used standardised extracts, not unidentified powder from unclear sources.
How common are side effects in the studies?
The numbers are reassuring. In the 2019 sleep study, where participants took 600 mg per day for ten weeks, no serious side effects were reported at all. In the 2012 stress study, 64 of 64 participants in the ashwagandha group completed the trial without anyone dropping out due to problems.
The same picture recurs in later studies: a handful of participants report mild stomach effects or drowsiness, at roughly the same rate as in the placebo groups. That does not mean side effects don't exist – only that they are uncommon at study doses over a limited time.
Bear in mind that the studies rarely run longer than twelve weeks. How the body responds to several years of daily intake is simply not known.
Which side effects are most common?
Here are the issues reported in studies and to authorities, roughly in descending order.
| Side effect | How common? | Comment |
|---|---|---|
| Stomach upset, loose stools | Most common | Reduced if you take the capsule with food |
| Nausea | Less common | Usually passes within the first week |
| Drowsiness | Less common | Can be turned into an advantage – take your dose in the evening |
| Headache | Uncommon | Drink enough water |
| Liver effects | Very rare | Isolated case reports, see below |
Noticing problems that don't settle within a week or two? Lower the dose or stop altogether. No supplement is worth an unsettled stomach every day.
A practical tip on the drowsiness: take your first few doses on an evening when you won't be driving, until you know how you react. Most people notice nothing, but there's no need to test the limit behind the wheel. If a morning dose makes you drowsy, simply move it to the evening – for many people that's actually an advantage.
Who should not take ashwagandha?
- Pregnant and breastfeeding women. Safety data is lacking, and the herb is traditionally advised against during pregnancy. Avoid it entirely.
- People with thyroid conditions. Ashwagandha can affect thyroid hormones. Talk to your doctor first.
- People with autoimmune conditions. The herb may stimulate the immune system. Check with your doctor.
- Before surgery. Stop at least two weeks before planned surgery, as ashwagandha can amplify anaesthetics and sedatives.
There are no studies in children and adolescents, so we also advise against use under 18. Not sure whether any of the above applies to you? A quick chat with a pharmacist costs nothing and gives you an answer straight away.
KSM-66 root extract with 500 mg per capsule – GMP-manufactured and third-party tested.
See current price »Ashwagandha and the liver – what do we know?
In 2020, a widely discussed case series was published in which five people in Iceland and the US developed liver problems after taking ashwagandha. All of them recovered. Set against the millions of doses sold every year, this is extremely rare.
In the controlled studies, where blood counts and liver values were often monitored, liver side effects have not been a problem. The risk factors in the case reports appear to be high doses and products without proper quality control. So always choose a third-party tested extract. Our ashwagandha is tested by an independent lab and manufactured to GMP standards.
Warning signs you should never ignore: yellowish skin or eyes, dark urine, itching and fatigue. If they appear, stop immediately and seek medical care.
Which medications can ashwagandha affect?
In theory, ashwagandha can amplify or interfere with certain medications. Always ask your doctor or pharmacist if you take any of the following:
- Thyroid hormone (for example levothyroxine)
- Sedatives and sleep medication – the drowsiness can be amplified
- Medication that lowers blood pressure or blood sugar
- Immunosuppressant medication
This is a food supplement, not a medicine. If you are ill or on medication, your doctor's advice always comes first.
How to reduce the risk of side effects
Four simple habits go a long way:
- Start with one capsule a day for the first week, then increase if needed.
- Take the capsule with a meal.
- Stick to the doses used in studies, usually 240–600 mg of extract per day. See our guide on ashwagandha dosage.
- Choose a standardised, third-party tested extract. In our comparison of the best ashwagandha you can see what sets the products apart.
Do the benefits outweigh the risks?
For healthy adults dealing with stress or sleep problems, the answer is usually yes. The studies show clear effects on stress and sleep, while the side effects are mild and uncommon. Do read our review of ashwagandha's effects according to the research before you decide.
If you belong to one of the risk groups above, the answer is instead: talk to a healthcare professional first. It takes five minutes and gives you an answer that applies to your specific situation. And whoever you are: never buy unidentified powder from unclear sources – that is where the problems tend to start.
Frequently asked questions
Can side effects appear as soon as you start?
Yes, the side effects that do occur tend to show up during the first few days. Most common are mild nausea, loose stools or drowsiness. The problems usually pass within a week once your body has adjusted. Taking the capsules with food and starting on a lower dose clearly reduces the risk.
Is ashwagandha dangerous for the liver?
Serious liver effects are very rare. A small number of case reports have been described in the research, often linked to high doses or products with unclear contents. In controlled studies using standardised root extract, liver side effects have not been a problem. If you develop yellowish skin, dark urine or itching, stop and seek medical care.
Can you take ashwagandha every day over a long period?
The studies usually run for 8 to 12 weeks, and during that time daily intake was well tolerated. Data on several years of use is lacking, however. A common practice is to pause for a few weeks after two to three months. There is no research-based requirement to take a break, but it is a cautious approach.
Does ashwagandha affect the thyroid?
Yes, it can. In a 2018 study, TSH values improved in people with subclinical hypothyroidism. That sounds positive, but if you take thyroid hormone the effect can throw off your carefully adjusted dose. If you have any thyroid condition, always check with your doctor before starting.
Can I combine ashwagandha with other supplements?
For healthy adults, ashwagandha usually combines well with common supplements such as magnesium, omega-3 or B vitamins. There are no known negative interactions between them. Be careful with other calming herbs, though, as the drowsy effect can be amplified. If you take medication, your pharmacist is the right person to ask.
Sources
- Chandrasekhar K et al. (2012). Ashwagandha root extract in reducing stress and anxiety: safety and efficacy. Indian J Psychol Med.
- Langade D et al. (2019). Efficacy and safety of ashwagandha root extract in insomnia and anxiety. Cureus.
- Björnsson HK et al. (2020). Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver Int.
- Sharma AK et al. (2018). Efficacy and safety of ashwagandha root extract in subclinical hypothyroid patients. J Altern Complement Med.
- Swedish Food Agency (Livsmedelsverket) – on food supplements and safety.
- EFSA – Botanicals: safety assessment of plant-based substances in food.
- 1177 (Swedish health service guide) – advice on medication use and when to seek care.