Ashwagandha is generally well tolerated at typical doses, but it carries a real list of side effects that range from mild digestive trouble to rare but serious liver injury. The most commonly reported issues are drowsiness, stomach upset, diarrhea, and vomiting. Less obvious effects, like shifts in thyroid hormones, emotional flattening, and drops in blood sugar, can catch people off guard, especially those already taking medication.
Digestive Problems
Stomach upset is the side effect you’re most likely to notice. Nausea, diarrhea, vomiting, and general abdominal discomfort are all reported in clinical trials. These symptoms tend to be dose-dependent, meaning higher amounts are more likely to cause trouble. Taking ashwagandha with food rather than on an empty stomach often reduces the irritation, though it doesn’t eliminate it for everyone.
Drowsiness and Sedation
Ashwagandha has calming properties, which is part of its appeal for stress and anxiety. But that same effect can tip into genuine drowsiness, especially at higher doses. Some people report persistent fatigue and low energy that goes beyond simple relaxation. One commonly described pattern involves taking large daily amounts (above 1,000 mg) and feeling exhausted throughout the day, with noticeably reduced motivation to exercise or stay active. If you’re taking anything else that causes drowsiness, including sleep aids, anti-anxiety medications, or sedatives, ashwagandha can amplify that effect.
Emotional Blunting
This is one of the less discussed side effects, but it comes up frequently among long-term users. Some people describe a loss of emotional range after weeks or months of use: less anxiety, yes, but also less excitement, less sadness, less motivation. The experience is sometimes described as “not caring about anything,” which can feel like relief at first and then become unsettling.
The mechanism likely involves ashwagandha’s influence on serotonin activity. In people whose brain chemistry responds strongly on the serotonin side, boosting it further while simultaneously blunting stress hormones may flatten emotional responses across the board. This isn’t something that shows up in short clinical trials, which typically run only 8 to 12 weeks, but it’s a well-recognized pattern among people who use ashwagandha for longer stretches. In traditional Ayurvedic medicine, this emotional dampening was actually considered a feature, used short-term to reduce agitation and craving during spiritual practice, not as a permanent state.
Thyroid Hormone Changes
Ashwagandha can meaningfully shift your thyroid hormone levels. In a clinical trial of 50 people with mildly underactive thyroids, taking 600 mg daily for eight weeks raised levels of both T3 and T4 (the two main thyroid hormones) and lowered TSH, the signal your brain sends to tell your thyroid to work harder. A separate study found that even 500 mg per day produced small increases in T4 in healthy men.
For someone with an underactive thyroid, this might sound like a benefit, but it creates real problems if you’re already taking thyroid medication. Ashwagandha can push your levels higher than intended, potentially causing symptoms of an overactive thyroid: rapid heart rate, weight loss, tremors, and anxiety. And if you have an overactive thyroid or Graves’ disease, ashwagandha could make things worse. Anyone on thyroid medication should be especially cautious, because the interaction could require dose adjustments that are hard to predict.
Liver Injury
Liver damage from ashwagandha is rare but documented. Case reports describe a pattern where users develop fatigue, jaundice (yellowing of the skin and eyes), nausea, and fever roughly one to several weeks into use or after increasing their dose. One published case involved a 36-year-old man whose liver enzymes spiked to more than 30 times the normal level after taking ashwagandha, with a liver biopsy confirming drug-induced injury. His levels began improving after he stopped the supplement.
Across the reported cases, the toxicity appears dose-dependent, with higher peaks in liver inflammation tied to recent increases in ashwagandha dosing. Recovery after stopping the supplement averaged about 3.5 months for liver markers to return to normal. The takeaway isn’t that ashwagandha is broadly dangerous to your liver, but that unexplained fatigue, dark urine, or yellowing skin while taking it should be taken seriously and not dismissed.
Medication Interactions
Beyond thyroid drugs, ashwagandha can interact with several common medication classes:
- Diabetes medications: Ashwagandha may lower blood sugar on its own, so combining it with insulin or oral diabetes drugs could cause blood sugar to drop too low.
- Blood pressure medications: Similar stacking effect. If you’re already on drugs that lower blood pressure, ashwagandha may push it further down, leading to dizziness or lightheadedness.
- Immunosuppressants: Ashwagandha stimulates the immune system, which directly works against medications designed to suppress it. This is especially relevant after organ transplants or during treatment for autoimmune diseases.
- Sedatives and anti-anxiety drugs: The combined drowsiness effect can become significant, affecting your ability to drive or function normally during the day.
Autoimmune Conditions
Ashwagandha’s ability to stimulate the immune system is a benefit for some people but a genuine risk for others. In autoimmune conditions like lupus, rheumatoid arthritis, or multiple sclerosis, the immune system is already attacking the body’s own tissues. Adding an immune stimulant on top of that can intensify flares and worsen symptoms. Memorial Sloan Kettering Cancer Center specifically warns that ashwagandha “can rev up your immune system even more, and that can be harmful” in people with autoimmune disorders.
Pregnancy Safety
There is not enough evidence to say ashwagandha is safe during pregnancy. Some traditional references and limited animal studies suggest it may have effects on uterine contractions at very high doses, though the evidence is thin and mostly based on ethnobotanical surveys rather than controlled studies. Australia’s Therapeutic Goods Administration reviewed the available data and concluded there is “insufficient anecdotal and clinical evidence to establish that ashwagandha is either safe in pregnancy or is used as an abortifacient.” At normal doses, the risk is unclear rather than confirmed, but the uncertainty itself is reason enough to avoid it during pregnancy and breastfeeding.
What Affects Your Risk
Most clinical trials that show ashwagandha to be well tolerated use standardized root extracts at 300 to 600 mg per day for 8 to 12 weeks. Side effects become more common and more severe at higher doses and with longer use. The form matters too: concentrated extracts deliver more active compounds per milligram than raw root powder, so the dose on the label doesn’t tell the whole story if you’re comparing products.
People who are otherwise healthy and not taking medications are least likely to run into problems. The risk profile shifts substantially if you have a thyroid condition, an autoimmune disease, liver issues, or take any of the medication classes listed above. Starting at a low dose and increasing gradually gives you the best chance of catching mild side effects before they become serious ones.