If you're taking ashwagandha or thinking about it, there are recent studies you should know about. While ashwagandha is marketed as a natural stress reliever and sleep booster, recent research has raised important safety questions.
This article walks through the latest data, not just on the benefits, because yes, ashwagandha does have some impressive therapeutic benefits, but also on potential toxicities. It explains who should and, more importantly, who should not take the supplement, along with hidden interactions with common medications to watch out for. At the end, we'll cover the best dose to take and how to choose the best ashwagandha brand if you and your doctor decide it's the right supplement for you.
Even though this information is written from a physician's perspective, it is not a substitute for personalized medical advice. Please talk to your doctor before making any changes to your health regimen, as the information here is educational only and not medical advice.
What Is Ashwagandha?
Ashwagandha is an adaptogen that has been used in Ayurvedic medicine for centuries and has gained significant attention in recent years for its potential benefits, particularly for stress, sleep, and possibly brain health and neuroprotection.
Small studies also show that ashwagandha can help with exercise recovery, muscle growth, and hormonal balance. However, caution is warranted in certain populations due to rare but very serious risks, which we'll cover in more detail below.
The Latest Evidence on Ashwagandha's Benefits
Sleep
The evidence on ashwagandha and sleep is fairly promising. A systematic review and meta-analysis of five randomized controlled trials with 400 participants showed a clinically beneficial effect of ashwagandha extract compared with placebo on sleep. The effects were observed in measures such as total sleep time, wake time after sleep onset, and sleep efficiency, with the most pronounced effects in adults diagnosed with insomnia who took at least 600 milligrams per day for at least 8 weeks.
There were, however, some notable limitations to this meta-analysis. Three of the five trials used actigraphy to measure participants' sleep quality objectively.
Actigraphy is a method where participants wear a device on their wrist or ankle. Even though actigraphy is widely used in sleep studies, it does not directly measure sleep quality; it measures movement, which is then used to estimate sleep-wake cycles. Ideally, the gold-standard assessment of sleep would be polysomnography, which is more expensive and performed in a laboratory setting.
Another limitation is that the sample sizes in all of these studies were fairly small, and the study duration was limited to 8 weeks.
Anxiety
Many people take ashwagandha for anxiety. A systematic review and meta-analysis of nine randomized controlled trials involving over 500 patients found that ashwagandha formulations had a significant beneficial effect on measures of anxiety and serum cortisol when compared to a placebo group.
One study examined the safety of ashwagandha and found that taking up to 300 milligrams twice daily for up to 8 weeks did not cause any adverse effects on hematologic and biochemical parameters. That said, most trials examining ashwagandha's effects were fairly small, had limited sample sizes, and lasted only 6 to 8 weeks. This is where the concerns begin.
Major Safety Concerns
Liver Toxicity
The most serious and well-documented complication associated with ashwagandha is herb-induced liver injury. This was first mentioned in the literature in 2017, in a case report of a 20-year-old man in Japan who developed severe intrahepatic cholestasis. In this condition, bile cannot flow properly from the liver.
This type of blockage leads to a buildup of bile acids in the liver and bloodstream, which can cause severe itching of the palms and soles. It may also cause dark urine and pale stools, and in severe cases, jaundice (yellowing of the skin or eyes).
Since then, multiple case reports from the US, Europe, and Asia have linked ashwagandha to liver injury. In most of these cases, researchers analyzed the chemical composition of the supplement consumed. They ruled out contamination from toxic compounds, meaning the ashwagandha supplement itself, not an outside toxin, caused the damage.
In a deep dive into these cases, the shortest reported time from first dose to onset of symptoms was only 2 weeks. In another case, in Iceland, the first symptom did not appear until after 12 weeks.
What causes this damage?
The specific substance suspected to be responsible for these liver-damaging effects is one of ashwagandha's metabolites, called withanone. A recent study revealed that withanone can cause DNA damage in liver cells, especially when the body's natural detox systems are overwhelmed. Normally, a natural chemical called glutathione neutralizes and removes harmful substances like withanone, but when the body's detox capacity is overwhelmed, damage can build up quickly. This is why taking ashwagandha can be especially risky for people with poor liver function or for those taking other hepatotoxic drugs, even something as mild as Tylenol.
These cases are rare, but rare side effects still matter when the consequences are serious and potentially preventable. It's advisable to avoid ashwagandha if you have any pre-existing liver conditions, such as hepatitis or fatty liver, or if you take other medications that may have toxic effects on the liver, including Tylenol, many antibiotics, and other supplements like green tea extract. If you do start ashwagandha, it's wise to have your liver labs checked 4 to 8 weeks after starting the supplement and to monitor them periodically after that, at least every 3 to 4 months during the first year.
Thyroid Function
Ashwagandha can also cause unexpected changes in thyroid function. In some cases, it may increase both T3 and T4 thyroid hormone levels. That might sound helpful for someone with low thyroid levels, but it can push healthy thyroid function into overdrive.
There are case reports of people developing heart palpitations, anxiety, headaches, diarrhea, and insomnia after using ashwagandha, only to later find their thyroid labs out of range. For these individuals, the average time for symptoms to appear was 2 months after starting ashwagandha. That delayed onset is part of the danger, since by the time symptoms show up, the damage is already underway.
If you have any thyroid issues, extra caution is warranted. Even without pre-existing thyroid conditions, it's a good idea to monitor thyroid function frequently, especially during the first 3 to 6 months after starting the supplement.
Medication Interactions
Ashwagandha can interact with other medications in important ways:
- Blood pressure medications: Ashwagandha can amplify the effects of these medications, potentially leading to dangerously low blood pressure.
- Diabetes medications and insulin: Ashwagandha can lower blood sugar, and combining it with these medications can cause an unsafe drop in blood sugar (hypoglycemia).
- Sedatives and anti-anxiety medications: Ashwagandha may cause excessive sedation or respiratory depression, and some people report emotional blunting or numbness.
- Pregnancy and breastfeeding: Ashwagandha is not recommended in this population, as there is no safety data available.
How to Take Ashwagandha Safely
None of this is meant to scare you away from ashwagandha. It's an incredibly powerful supplement with real benefits, and the vast majority of people do very well on it. Still, it's important to be careful. If you are going to take ashwagandha, discuss it with your doctor first, and keep the following in mind.
Dose matters. Most clinical trials use doses of 300 to 600 milligrams per day. It's wise to be hesitant about taking anything higher, since higher doses don't necessarily mean more benefit, just more potential for side effects.
Consider cycling. Since most studies on ashwagandha have been short-term (no more than 8 weeks) and there is no long-term safety data, it may be worth taking breaks from ashwagandha and cycling on and off roughly every 6 to 8 weeks. This gives the body time to recalibrate and may reduce the risk of side effects and toxicity building up slowly.
Avoid it if you have liver issues. Do not take ashwagandha if you have any liver issues, and be extremely cautious with it if you have an underlying thyroid issue.
Get baseline labs. Even without any of these conditions, it's a good idea to get a baseline set of labs to measure liver and thyroid function before starting ashwagandha, and to monitor labs at least every 3 to 6 months while taking it, depending on other health conditions.
Choosing the Right Ashwagandha Supplement
One of the most overlooked but most important decisions when taking ashwagandha is picking the right supplement. Unfortunately, the supplement industry, at least in the US, is not well-regulated so that quality can vary widely between brands.
When choosing a brand, look for labels that say NSF Certified or USP Verified, which indicate that the product has been third-party tested, actually contains what it claims, and is free of contaminants such as heavy metals.
It's also wise to avoid proprietary blends labeled simply as "ashwagandha complex" that don't specify how much of the actual extract is included. That's a red flag, because dose matters significantly with ashwagandha, and just like with many medications or supplements, the dose is what makes the poison.
Be especially careful with ashwagandha gummies. Many wellness brands add a small amount of ashwagandha to a sugar-filled gummy and market it as a stress solution. These gummies often do not contain therapeutic levels of ashwagandha and frequently lack standardization or third-party testing. Not all gummies are like this, but many are, so caution is warranted.
FAQ
Is ashwagandha safe to take every day?
For most healthy people, short-term use within studied doses (300 to 600 mg per day) appears to be well tolerated. However, since long-term safety data are lacking, cycling on and off every 6 to 8 weeks may be a safer approach.
Can ashwagandha damage the liver?
In rare cases, yes. Multiple case reports link ashwagandha to herb-induced liver injury, with symptoms sometimes appearing as early as 2 weeks or as late as 12 weeks after starting the supplement.
Who should avoid ashwagandha?
People with pre-existing liver conditions, those taking hepatotoxic medications, individuals with thyroid conditions, and pregnant or breastfeeding women should avoid ashwagandha or use it only under close medical supervision.
Does ashwagandha interact with medications?
Yes. It can interact with blood pressure medications, diabetes medications, and insulin, and sedative or anti-anxiety medications, potentially causing low blood pressure, low blood sugar, or excessive sedation.
What is the best dose of ashwagandha?
Most clinical trials use 300 to 600 milligrams per day. Higher doses have not been shown to provide additional benefit and may increase the risk of side effects.
How do I choose a good ashwagandha supplement?
Look for products labeled NSF Certified or USP Verified, avoid vague "proprietary blends," and be cautious with gummies, which often lack therapeutic doses and third-party testing.
Conclusion
Ashwagandha remains a promising adaptogen with real, evidence-backed benefits for sleep, anxiety, and stress. At the same time, emerging case reports on liver toxicity and thyroid dysfunction highlight the importance of using it thoughtfully. Anyone considering ashwagandha should talk to their doctor first, choose a well-tested, reputable product, stick to studied dosing ranges, and monitor relevant lab work, particularly liver and thyroid function, before and during use. With the right precautions, most people can use ashwagandha safely, but awareness of these risks is essential for making an informed decision.