Ashwagandha Side Effects, Dangers and Contraindications

The verdict in brief

Ashwagandha is well tolerated, but not by everyone.

Ashwagandha (Withania somnifera) is a plant from Ayurvedic medicine, in the nightshade family, like tomatoes and deadly nightshade. The root is the part mostly used, rich in withanolides, molecules similar to steroids. It is one of the best-studied plants in its category: several dozen controlled trials in adults, lasting from a few weeks to a few months. If you first want to know what those trials observed, our guide ashwagandha benefits: what the studies really show covers it.

In these trials, adverse effects are rare, mild, and often just as frequent in the placebo group. But an eight-week trial on a few dozen healthy volunteers cannot pick up an effect that affects one person in several thousand. That is exactly the profile of liver injury: rare, unpredictable, and discovered through reports after the product reached the market.

So remember two things. For a healthy adult who sticks to the dose, the risk is low. And that risk is not zero: it justifies a few simple precautions, set out below.

Common side effects

Ashwagandha side effects: digestion and sleep first.

The ashwagandha side effects reported in trials are almost always benign. They generally appear in the first few days, and go away when you lower the dose or change the time you take it.

Summary of adverse effects reported in clinical trials in adults. Any symptom that lasts or gets worse means you should stop and talk to a doctor.

The morning “hangover” that many people describe on forums is mostly explained by a high dose taken just before bed. The plant was named somnifera for a reason: in some people, it causes drowsiness. That is not dangerous in itself, but take it seriously before driving or if you already take a medicine that makes you sleepy.

So the time you take it matters as much as the dose. Our article on how to lower cortisol puts ashwagandha in context alongside other levers, many of which have nothing to do with a supplement.

The liver: the real risk

Ashwagandha and the liver: rare, but worth knowing about.

Since the late 2010s, liver specialists have described patients whose liver was damaged after taking ashwagandha supplements. The first major series came from Iceland and the US DILIN network, which specialises in liver injury caused by medicines and supplements. Other cases followed, in Europe, India and the United States, between 2020 and 2024. The LiverTox database, run by the US National Institutes of Health, now lists ashwagandha among the possible, but rare, causes of liver injury.

The picture described is fairly consistent. Most often it is a so-called cholestatic or mixed hepatitis: bile does not flow properly, causing jaundice and sometimes intense itching. Symptoms appear after a few weeks of use. In the vast majority of cases, everything returns to normal once the supplement is stopped, within one to several months. Severe forms have been reported, mainly in people who already had liver disease.

How often does it happen? Nobody can give a precise figure, because the exact number of users is unknown. Set against the millions of people who take it worldwide, the number of published cases remains very low. But most supplement-related liver injuries are never published, and many cases involve several plants: so it is hard to put the blame on ashwagandha alone.

These signs are not specific to ashwagandha: they apply to any supplement, and to many medicines. Knowing them is enough to turn a rare risk into a managed one, because liver injury spotted early and followed by prompt withdrawal usually heals without lasting damage. Our article on the risks of mushrooms and adaptogenic plants applies the same logic to the other ingredients in the category.

Ashwagandha and the thyroid

A plant that shifts thyroid hormones.

Ashwagandha and the thyroid is the question many readers ask, often after reading that it “helps” with hypothyroidism. The starting point is the Sharma trial: in people whose thyroid was running slightly slow, eight weeks of extract raised T4 and lowered TSH. Cases of hyperthyroidism, and even thyrotoxicosis, have also been described in people taking ashwagandha.

This action on the thyroid is not good news for self-medication. If you are treated with levothyroxine, a plant that also raises T4 can upset a dose adjusted to the microgram. If you have hyperthyroidism or Graves' disease, it can make things worse. And if you take an antithyroid drug, it can work against the treatment.

• Treated hypothyroidism: no ashwagandha without your doctor's agreement, so they can monitor your TSH.
• Hyperthyroidism, Graves' disease, toxic nodule: avoid it.
• Hashimoto's: ANSES advises against the plant for any thyroid disease, whatever the type.
• Thyroid test coming up: tell your doctor you take it, as it can change the results.
• Palpitations, tremors, unexplained weight loss on ashwagandha: stop and see a doctor.

This is one of the reasons why the ANSES opinion explicitly lists thyroid conditions among the at-risk situations. The plant is not a thyroid treatment, and it should not be used as one.

Who should avoid it

Pregnancy, breastfeeding, children: the answer is no.

In 2024, the French health agency ANSES published an opinion on food supplements containing ashwagandha, following reports received through its nutrivigilance scheme. The agency does not ban the plant, but it advises several groups against taking it, because of a lack of safety data, effects observed in animals and humans, and a traditional use to induce miscarriage.

To be on the safe side, add to this list people with an autoimmune disease (lupus, rheumatoid arthritis, multiple sclerosis), because ashwagandha seems to stimulate certain immune functions, and anyone due to have surgery: stop at least two weeks beforehand, because of the sedative effect that can add to the anaesthetic.

Men on hormone treatment, particularly for the prostate, should also talk to their doctor: a few trials have observed a rise in testosterone with ashwagandha. Finally, the plant belongs to the nightshade family: a known allergy to this family is one more reason to avoid it.

Interactions

Medicines not to combine without medical advice.

Most of ashwagandha's interactions are theoretical: they follow from what the plant does in the body, not from well-documented incidents. That is no reason to ignore them. Here are the families of medicines concerned.

Not an exhaustive list. If you are on long-term treatment, show the supplement label to your pharmacist before you start.

The same logic applies to combining plants: mixing several calming plants, such as ashwagandha, valerian or melatonin, increases drowsiness. That is often the point in the evening, much less so behind the wheel.

Status in France and Europe

Allowed in France, banned in Denmark.

In France, ashwagandha is not banned in food supplements. The 2024 ANSES opinion recommends restrictions by group and calls for better consumer information, without changing the legal framework for healthy adults. We will devote a full article to the question “is ashwagandha banned in France?”, because it comes up very often.

Denmark made a different choice. The Technical University of Denmark (DTU) issued an assessment in 2020 concluding that it could not set a risk-free dose, notably because of possible effects on sex hormones, the thyroid and pregnancy. On that basis, the Danish authorities banned the plant in supplements in 2023. The assessment was criticised, in particular because it did not distinguish the root from the leaves, but the ban was applied. Other Nordic countries have since looked into the question.

These differences do not mean one country is right and the other wrong. They reflect the same uncertainty, handled with more or less caution. If you are hesitant, other plants in the same category exist, such as rhodiola or holy basil, each with its own precautions. Our reishi or ashwagandha comparison can also help you choose.

Choosing a safe product

Choosing your ashwagandha, in four checks.

Part of the risk lies in the product itself: a poorly identified powder, root mixed with leaves, heavy metal contamination or a fanciful dose. A few checks are enough to rule out bad products.

The fourth check, and the simplest: the dose and what the label says. A product that does not mention the contraindications (pregnancy, thyroid, under 18s) is not playing fair. At Mush n Go, ashwagandha goes into Anti-Stress, as an extract standardised for withanolides, and into Brainstoorm. Our laboratory analyses are available to view, and that is something some customers point out.

Real Trustpilot review, quoted as is. Our products containing ashwagandha are not recommended for the same groups as those listed above.

And a common-sense rule on duration: take it in courses of a few weeks, as in the trials, followed by a break, rather than continuously for years. To find out all about the plant itself, see our ashwagandha page.

Sources

1. Björnsson H. K., Björnsson E. S., Avula B. et al. (2020). Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver International, 40(4), 825-829.
2. Philips C. A., Valsan A., Theruvath A. H. et al. (2023). Ashwagandha-induced liver injury: a case series from India and literature review. Hepatology Communications, 7(10), e0270.
3. Sharma A. K., Basu I., Singh S. (2018). Efficacy and safety of ashwagandha root extract in subclinical hypothyroid patients: a double-blind, randomized placebo-controlled trial. Journal of Alternative and Complementary Medicine, 24(3), 243-248.
4. Chandrasekhar K., Kapoor J., Anishetty S. (2012). 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, 34(3), 255-262.
5. ANSES (2024). Opinion on the risks associated with the consumption of food supplements containing ashwagandha (Withania somnifera). Request no. 2021-SA-0077.
6. DTU Fødevareinstituttet (2020). Risk assessment of Withania somnifera (ashwagandha), report for the Danish Veterinary and Food Administration. Technical University of Denmark.
7. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Ashwagandha. National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda.

Keep reading

Further reading.

Ashwagandha is only one of the options for dealing with stress. Explore our other guides, or our page dedicated to the plant.