Ashwagandha is generally well tolerated in short-term use, but it does carry real side effects ranging from mild digestive issues to rare but serious liver injury. Most people who take it at standard doses (300 to 600 mg of root extract daily) experience nothing worse than an upset stomach or drowsiness, yet the supplement has drawn enough safety concerns that Denmark and Sweden have restricted its sale.
Common Side Effects
The most frequently reported side effects are gastrointestinal: stomach upset, loose stools, nausea, and occasionally vomiting. Drowsiness is also common, which makes sense given that ashwagandha is often marketed for stress and sleep. Clinical trials lasting up to three months consistently describe these effects as mild, and they tend to resolve on their own or after lowering the dose.
These digestive symptoms appear more often at higher doses. Trials have tested anywhere from 240 mg to 1,250 mg of extract per day, and the range considered effective for anxiety by an international psychiatric taskforce is 300 to 600 mg daily. If you’re experiencing stomach problems, you may simply be taking more than you need.
Liver Injury: Rare but Documented
The most serious known risk is liver damage. At least five published cases describe people, ranging from age 21 to 62, who developed signs of liver injury after taking 450 to 1,350 mg of ashwagandha daily for as little as one week or as long as four months. The pattern across these cases looks similar: nausea, itching, dark urine, and jaundice (yellowing of the skin or eyes).
Two well-documented cases illustrate the timeline. A 36-year-old man developed symptoms after six months of use at 450 mg three times daily. A 30-year-old woman developed itching after just 45 days on 450 mg. In both cases, liver function markers were elevated, but they improved within two weeks of stopping the supplement and returned to normal within four to eight weeks. Across all documented cases, every patient recovered after discontinuation, and no deaths were reported. One person, however, required a liver transplant.
This doesn’t mean ashwagandha is broadly dangerous to your liver. These cases are rare relative to how widely the supplement is used. But they do mean that unexplained nausea, itching, dark urine, or yellowing skin while taking ashwagandha should be taken seriously and warrants stopping the supplement immediately.
Effects on Thyroid Hormones
Ashwagandha directly stimulates the thyroid gland to produce more of its two main hormones, T3 and T4. As those levels rise, the brain’s signaling hormone (TSH) drops in response. For someone with an underactive thyroid, this might sound appealing, but it creates a real problem for anyone with an overactive thyroid or anyone already taking thyroid medication.
If you have hyperthyroidism, ashwagandha can amplify the symptoms you’re already dealing with: irritability, restlessness, hand tremors, heart palpitations, and anxiety. Even people with normal thyroid function who take thyroid hormone medication could see their levels pushed out of range. This interaction is significant enough that the NIH specifically lists thyroid medications among the drugs that ashwagandha may interfere with. Denmark’s 2020 safety review flagged the thyroid effects as a primary concern behind its decision to restrict sales.
Drug Interactions to Know About
Beyond thyroid drugs, ashwagandha can interact with several medication classes. The NIH identifies interactions with:
- Diabetes medications. Ashwagandha can lower blood sugar on its own, so combining it with diabetes drugs raises the risk of blood sugar dropping too low. Signs of this include dizziness, confusion, trembling, sweating, and a rapid heartbeat.
- Blood pressure medications. Similar logic applies here. If ashwagandha lowers your blood pressure and your medication does the same, the combined effect could leave you lightheaded or faint.
- Sedatives. Because ashwagandha causes drowsiness, pairing it with sedative medications can amplify that effect beyond what’s comfortable or safe.
- Anti-seizure medications. The interaction mechanism isn’t fully characterized, but there’s enough evidence for it to appear on the NIH’s caution list.
- Immunosuppressants. Ashwagandha appears to boost immune activity, which works against drugs designed to suppress the immune system. This is particularly relevant for people with autoimmune conditions like lupus, multiple sclerosis, or rheumatoid arthritis, or for anyone who has received an organ transplant.
Pregnancy and Breastfeeding
Ashwagandha is traditionally considered unsafe during pregnancy. The World Health Organization advises against its use during pregnancy and breastfeeding, citing historical reports from Ayurvedic medicine that the root was used to induce abortions. No modern clinical trial has tested this directly, so the evidence is based on traditional use rather than controlled studies. Still, the combination of its hormonal activity and this historical concern is enough that avoiding it during pregnancy is the standard recommendation.
Regulatory Warnings in Europe
Denmark banned ashwagandha in food supplements after a 2020 safety review by the Danish Technical University concluded it could have harmful effects on thyroid and sex hormones. Sweden followed with its own sales ban. In October 2024, the European Commission’s food safety alert system issued a notification classifying ashwagandha supplements as a “potential risk,” leading to further removal of products from online marketplaces.
The United States has not restricted ashwagandha, and it remains widely available as a dietary supplement. But the European actions reflect growing concern that a supplement sold for stress relief carries hormonal and hepatic risks that many consumers aren’t aware of.
How Long Is It Safe to Take?
Most clinical trials have only tracked participants for about three months, so that’s the outer boundary of what researchers can confidently call “well tolerated.” The liver injury cases involved use ranging from one week to six months, which means problems can emerge at any point. There’s no established safe duration for long-term use, and cycling on and off (rather than taking it indefinitely) is a common practical approach, though it hasn’t been formally studied either.
If you’re taking ashwagandha and notice new symptoms, particularly drowsiness that interferes with daily life, digestive problems that don’t improve, or any signs of liver trouble like dark urine or yellowing skin, stopping the supplement is the most important first step. In documented cases, that alone was enough for a full recovery.