Ashwagandha Side Effects: What Research Actually Shows

Ashwagandha’s most common side effects are mild — stomach upset, drowsiness, and headache. But it’s also been linked to rare cases of liver injury, thyroid hormone changes, and interactions with several common medications, and it’s considered unsafe during pregnancy. Most healthy adults tolerate it well at standard doses, but the risk changes depending on your health history.

If you take thyroid medication, have an autoimmune condition, are pregnant, or are on prescription drugs for blood pressure, blood sugar, or your immune system, the details below matter for you specifically. Here’s what the research actually says.

Who Uses Ashwagandha, and Why

Ashwagandha is one of the most widely used herbs in Ayurvedic medicine, a traditional system of medicine from India that’s been practiced for thousands of years. Today, it’s sold as an over-the-counter supplement, and most people who take it fall into a few common groups:

• People managing everyday stress — it’s the single most common reason people try ashwagandha. Its reputation as an “adaptogen” (a substance thought to help the body handle stress) comes largely from research showing it can lower cortisol, the body’s main stress hormone.
• People looking for better sleep — often the same audience as above, since lower stress and calmer nervous system activity tend to support sleep quality.
• Athletes and weightlifters — some research has examined ashwagandha for muscle strength, recovery, and endurance, which has made it popular in the fitness and supplement world.
• People with mild anxiety symptoms — several clinical trials have studied ashwagandha as a complementary option for anxiety, generally finding modest improvements compared to placebo over 8-week periods.
• People with an underactive thyroid — some research suggests it may help support thyroid hormone levels in this specific group.

For the vast majority of people trying ashwagandha for these everyday reasons — stress, sleep, mild anxiety, general wellness — the research points to a favorable safety profile at normal doses. The more serious risks tend to cluster around specific circumstances: much higher doses than recommended, long-term continuous use, pregnancy, or an existing health condition like thyroid disease. Knowing those specifics is what lets you use it thoughtfully rather than either ignoring the risks or assuming the worst.

Ashwagandha Side Effects at a Glance

• Stomach upset, nausea, diarrhea — Common, usually mild. Anyone can experience this, especially on an empty stomach.
• Drowsiness, sedation — Common. Higher risk for people also taking sedatives, sleep aids, or alcohol.
• Headache — Occasional. Can affect anyone.
• Liver injury (jaundice, elevated liver enzymes) — Rare but documented. More likely with high doses or long-term use.
• Thyroid hormone changes — Uncommon. Higher risk for people with hyperthyroidism, Hashimoto’s, or those on thyroid medication.
• Low blood pressure or blood sugar — Uncommon. Higher risk for people on antihypertensives or diabetes medication.
• Miscarriage risk — Not well quantified in humans, but flagged as a risk. Considered a contraindication for pregnant women.
• Allergic reaction — Rare. Higher risk for people with plant/nightshade sensitivities.

The Common, Mild Side Effects

For most people, ashwagandha’s side effects look a lot like what you’d expect from any new supplement — a mildly unsettled stomach for the first week or two.

Digestive symptoms are the most frequently reported issue in clinical trials and include:

• Nausea
• Stomach cramping
• Diarrhea or loose stools
• Loss of appetite

Taking it with food, rather than on an empty stomach, tends to reduce these effects.

Drowsiness and sedation are also common, which tracks with how ashwagandha is thought to work. It has GABAergic activity — meaning it interacts with the same calming neurotransmitter system as benzodiazepines and some sleep medications — which is part of why it’s marketed for stress and sleep in the first place. That same mechanism is why people combining it with sedatives, alcohol, or antihistamines sometimes notice excessive grogginess or slowed reaction time.

Headaches show up less often but are still reported in placebo-controlled trials at a low rate.

A systematic review found that ashwagandha didn’t alter liver function markers in this population — reassuring for short-term use in otherwise healthy people, though it doesn’t rule out risks with longer-term or higher-dose use, which is where most serious case reports come from.

Liver Injury: Rare, But Real

This is the side effect that’s drawn the most medical attention in the last few years, and it’s worth taking seriously even though it’s uncommon.

Since 2019, case reports and case series have documented herb-induced liver injury linked to ashwagandha, ranging from jaundice and itching to, in at least one instance, liver failure requiring a transplant.

A 2023 case series reviewed 23 patients with liver injury linked to ashwagandha use between 2019 and 2022, with cholestatic hepatitis (a pattern involving impaired bile flow) as the most common presentation. A separate 2023 review used a formal causality assessment tool for new cases and found a “probable” relationship between ashwagandha and liver injury in both patients studied, with recovery after stopping the supplement.

More recent case reports, including one published in 2024 describing a 22-year-old woman who developed jaundice within 30 hours of starting ashwagandha capsules, continue to add to this pattern.

A few things stand out across these reports:

• Symptoms typically appeared weeks to months after starting ashwagandha, though one case occurred within 30 hours.
• Several cases involved doses at or above label recommendations  (some as high as 1,950 mg/day).
• Symptoms — jaundice, dark urine, itching, fatigue — generally resolved after stopping the supplement.
• Meanwhile, meta-analyses of controlled trials in healthy volunteers using standard doses have generally found no measurable effect on liver enzymes, according to the 2023 systematic review mentioned above and an earlier 2021 meta-analysis of 615 subjects.

The takeaway many clinicians draw from this is dose-dependent: liver injury appears to be a real but low-frequency risk that’s more associated with high or prolonged dosing than with typical short-term, label-dose use. If you notice yellowing skin or eyes, unusually dark urine, persistent itching, or unexplained fatigue while taking ashwagandha, stop and see a doctor.

Effects on Thyroid Hormones

Research on people with hypothyroidism (underactive thyroid) has generally been framed as a potential benefit: one 8-week trial found that 600 mg/day of ashwagandha root extract raised T3 and T4 levels compared to placebo. But that same mechanism is a liability for anyone whose thyroid is already overactive.

There’s no dedicated human trial testing ashwagandha specifically in people with hyperthyroidism, but case reports fill in the gap. A 2022 case report described a 73-year-old woman who developed thyrotoxicosis — a state of dangerously high thyroid hormone — after two years of self-administered ashwagandha use, with full resolution after she stopped. Another case report documented a younger patient who developed hyperthyroid symptoms, an enlarged and tender thyroid, and abnormal labs after several months of high-dose use, again resolving after discontinuation.

A 2026 review evaluating ashwagandha’s hormonal effects notes that results across studies are mixed and depend heavily on baseline thyroid status — euthyroid people (normal thyroid function) often show little change, while people with existing thyroid dysfunction are more likely to see meaningful shifts in either direction.

If you have hyperthyroidism, Graves’ disease, or Hashimoto’s thyroiditis, or you take levothyroxine or a similar medication, talk to your doctor before adding ashwagandha, and get thyroid panels rechecked periodically if you do use it together, since levels can shift over roughly 8 weeks.

Blood Pressure and Blood Sugar Effects

Ashwagandha is often marketed as supporting healthy blood sugar and blood pressure, and for people without underlying conditions, that’s generally not an issue. But the same mechanism that makes it appealing for metabolic health is exactly what creates risk for people already on medication for these conditions.

The concern isn’t that ashwagandha causes dangerously low blood pressure or blood sugar on its own — it’s the additive effect when it’s combined with drugs already doing that job. The NIH Office of Dietary Supplements and the Merck Manual both list antihypertensives and antidiabetic medications among the drug classes that may interact with ashwagandha.

In practice, this means someone on metformin, insulin, or a sulfonylurea could see blood sugar drop lower than expected, and someone on an ACE inhibitor, beta-blocker, or calcium channel blocker could experience more pronounced blood pressure drops — with symptoms like dizziness, lightheadedness, or fatigue.

This is manageable with awareness. If you’re on medication for either condition and want to try ashwagandha, monitoring your levels a bit more closely in the first few weeks (home blood pressure checks, blood glucose logs) can catch a problem early, and your prescriber may want to adjust dosing rather than have you stop the medication or the supplement outright.

Allergic Reactions

Ashwagandha belongs to the nightshade (Solanaceae) family, along with tomatoes, potatoes, and peppers. True allergic reactions appear to be uncommon in the clinical literature, but they’re not zero. Reported symptoms of an allergic response include:

• Skin rash or hives
• Facial swelling
• Difficulty breathing (in more severe cases)
• Itching without an obvious cause

If you have known sensitivities to nightshade plants, or you develop any of these symptoms after starting ashwagandha, stop use and seek medical attention if breathing is affected.

Why Side Effects Vary So Much From Person to Person

One reason ashwagandha’s side-effect profile looks so inconsistent across articles and personal anecdotes is that “ashwagandha” isn’t one standardized thing. Products differ in:

• Which part of the plant is used — root extract, leaf extract, or a combination, which has different chemical profiles
• Concentration and standardization — often measured by withanolide content, which varies by manufacturer
• Dose — label doses range widely, and some products pack considerably more per serving than what’s used in clinical trials
• Duration of use — most trials run 8–12 weeks; real-world use is often much longer
• Individual health status — baseline thyroid function, liver health, medication use, and pregnancy status all change the risk calculus substantially

This variability is part of why case reports of serious side effects often involve doses above what’s typically studied, while controlled trials at standard doses tend to report a much milder side-effect profile. It’s also why “ashwagandha is safe” and “ashwagandha caused my liver injury” can both be accurate statements depending on the dose, product, and person involved.

Hormonal and Reproductive Effects

Beyond the thyroid, ashwagandha appears to influence cortisol and sex hormones. Multiple studies consistently show it lowers cortisol, which is the basis for its “stress relief” reputation, and some research indicates it can raise testosterone in men and affect estrogen and other reproductive hormones in women, according to a 2026 hormonal safety review. For most adults, this isn’t dangerous, but it’s a relevant consideration if you have a hormone-sensitive condition or are on hormonal therapy.

Pregnancy and Breastfeeding

This is one of the clearer contraindications in the research.

Modern safety reviews — including the NIH Office of Dietary Supplements fact sheet — advise against use during pregnancy on this basis. A 2020 risk assessment by the Technical University of Denmark examined this alongside ashwagandha’s effects on thyroid and sex hormones, and Denmark subsequently banned ashwagandha products in 2023.

A 2025 prospective trial studied ashwagandha root extract in 70 pregnant women in their second trimester, looking at anemia, stress, and sleep alongside safety markers — a signal that research interest in this area is growing. But this remains a single small study, not the kind of large, replicated safety evidence that would override existing caution. Given the conflicting and still-limited data, the consistent recommendation from major health bodies is to avoid ashwagandha during any trimester of pregnancy, and there isn’t enough safety data on breastfeeding to recommend it there either.

Drug Interactions to Know About

According to the NIH fact sheet and the Merck Manual’s professional reference, it may interact with:

• Thyroid medications (levothyroxine and similar) — risk of pushing thyroid hormone levels too high
• Diabetes medications — ashwagandha may lower blood sugar, which, combined with insulin or other glucose-lowering drugs, could increase hypoglycemia risk
• Blood pressure medications — similar concern, since ashwagandha may have a mild blood-pressure-lowering effect
• Immunosuppressants (such as tacrolimus, cyclosporine, or corticosteroids) — ashwagandha’s immune-modulating activity could theoretically work against drugs meant to suppress immune function
• Sedatives, benzodiazepines, and sleep medications — additive drowsiness or central nervous system depression is possible given ashwagandha’s GABAergic activity

None of this means these combinations are automatically dangerous, but it does mean they’re worth a conversation with a pharmacist or doctor, particularly if you’re on a narrow-therapeutic-window medication like a blood thinner, immunosuppressant, or thyroid hormone replacement.

Who Should Be Cautious or Avoid Ashwagandha

Based on the research above, a few groups stand out as needing extra caution:

• Pregnant or breastfeeding individuals — considered a contraindication
• People with hyperthyroidism, Graves’ disease, or unstable Hashimoto’s — risk of worsening thyroid hormone imbalance
• People with certain autoimmune conditions (lupus, rheumatoid arthritis, multiple sclerosis) — ashwagandha’s immune-stimulating properties could theoretically aggravate autoimmune activity, though direct evidence in humans is still limited
• People with existing liver disease, or anyone taking other medications known to stress the liver
• Anyone on sedatives, diabetes medication, blood pressure medication, or immunosuppressants — see interactions above
• People scheduled for surgery — some clinicians recommend stopping ashwagandha roughly two weeks beforehand because of its central nervous system and blood sugar effects

If you fall into any of these categories, this is a “talk to your doctor first” situation rather than an automatic no — but it’s not one to guess your way through.

How to Reduce Your Risk of Side Effects

If you and your doctor have decided ashwagandha is reasonable for you, a few practical habits lower the odds of problems:

1. Stick to studied doses. Most clinical trials use 300–600 mg/day of standardized root extract. Several of the liver injury case reports involved doses well above this (some over 1,000 mg/day).

2. Take it with food to reduce nausea and stomach upset.

3. Don’t combine it with alcohol or sedatives without medical guidance, given the additive drowsiness risk.

4. Get baseline labs if you’re on long-term therapy — particularly thyroid panels and liver enzymes — and recheck periodically.

5. Watch for early warning signs of liver trouble: yellowing skin or eyes, dark urine, persistent itching, unusual fatigue, or abdominal pain. Stop and seek care if these appear.

6. Don’t assume “natural” means risk-free. Ashwagandha is a bioactive compound, and its safety profile — like any supplement — depends on dose, duration, and your individual health status.

When to See a Doctor

Stop taking ashwagandha and contact a healthcare provider if you notice:

• Yellowing of the skin or eyes
• Dark-colored urine or unusually pale stools
• Persistent itching without a rash
• Signs of a fast heart rate, unexplained weight loss, or heat intolerance (possible thyroid overactivity)
• Unusual bleeding, bruising, or signs of low blood sugar (shakiness, confusion, sweating) if you’re on relevant medications
• Any new or worsening symptoms that coincide with starting the supplement

What We Still Don’t Know

It’s worth being upfront about the limits of current research, since much ashwagandha marketing overstates how settled the science is.

• Long-term data is thin. Most clinical trials run 8 to 12 weeks. Very little controlled research has followed people using ashwagandha continuously for a year or more, so effects that build up slowly — on the liver, thyroid, or hormones — may not yet be fully captured.
• Product quality isn’t standardized. Because ashwagandha is sold as a supplement rather than a regulated drug in most countries, potency, purity, and contaminant testing vary by brand. Some documented liver injury cases have involved products where dosing didn’t match the label.
• Pregnancy research is genuinely limited. A small number of newer trials are beginning to examine ashwagandha in pregnant women for specific outcomes such as anemia and sleep, but the overall body of evidence remains too small to override existing caution.
• Interaction data is often theoretical. Many drug interaction warnings are based on ashwagandha’s known mechanisms (lowering cortisol, affecting thyroid hormones, and GABAergic activity) rather than on large-scale clinical interaction studies. That doesn’t make the concern invalid, but it does mean the actual magnitude of risk in a real person combining, say, ashwagandha and levothyroxine isn’t precisely quantified.

None of this means ashwagandha is unusually risky compared to other supplements — but it does mean “more research needed” is a fair and honest summary of where several of these questions stand.

Frequently Asked Questions

Is ashwagandha safe to take every day?

For most healthy adults, standard doses (300–600 mg/day of root extract) used for up to a few months appear to be well tolerated in clinical trials. Long-term safety data beyond several months is more limited, and higher doses carry more documented risk.

Can ashwagandha damage your liver?

It can, though this appears to be rare and more closely tied to high doses or prolonged use. Multiple case reports since 2019 describe liver injury that resolved after stopping the supplement, while controlled trials at standard doses in healthy volunteers have generally not shown liver enzyme changes.

Does ashwagandha affect the thyroid?

Yes, it can raise T3 and T4 levels, which may help people with an underactive thyroid but can be risky for those with an overactive thyroid or unstable autoimmune thyroid disease. Anyone on thyroid medication should monitor levels if combining it with ashwagandha.

Who shouldn’t take ashwagandha?

Pregnant or breastfeeding individuals, people with hyperthyroidism or unstable autoimmune thyroid conditions, and anyone with existing liver disease should avoid it or use it only under medical supervision. People on sedatives, diabetes medication, blood pressure medication, or immunosuppressants should check with a doctor first.

What are the first signs of a bad reaction to ashwagandha?

Early signs to watch for include nausea, unusual fatigue, itching, dark urine, or yellowing skin and eyes. Milder reactions like stomach upset or drowsiness are far more common and usually not a cause for concern unless they’re severe or persistent.

How long do ashwagandha side effects last?

Mild digestive symptoms and drowsiness typically fade within the first one to two weeks as your body adjusts, or resolve quickly once you lower the dose. More serious effects, like liver injury or thyroid hormone changes documented in case reports, have generally resolved within weeks to a few months after stopping the supplement, though recovery time varies by individual and severity.

Can you take ashwagandha long-term without side effects?

Some people do use it for months at a time without apparent problems, but the controlled research backing its safety mostly covers 8- to 12-week windows. Longer-term use hasn’t been studied as thoroughly, so periodic breaks and occasional bloodwork (especially liver and thyroid panels) are a reasonable precaution if you’re using it continuously for an extended period.