Several popular supplements can cause serious liver damage, and some have led to liver failure and even death. The biggest offenders include green tea extract in concentrated form, kava, certain herbal products containing toxic plant compounds, high-dose vitamin A, bodybuilding supplements with hidden steroids, and more recently, ashwagandha. Because dietary supplements aren’t tested for safety before they hit store shelves the way prescription drugs are, the burden falls on you to know which ones carry real risk.
Green Tea Extract
Drinking green tea is generally safe. The problem starts with concentrated green tea extract supplements, which pack far more of the active compound EGCG into a single capsule than you’d ever get from a cup of tea. Doses above 800 mg of EGCG per day have been shown to raise liver enzymes, a direct sign of liver cell damage. The European Food Safety Authority reviewed the evidence and concluded it wasn’t possible to identify a dose of EGCG from supplements that could be considered universally safe.
Most of the harm comes from weight loss and “detox” products that list green tea extract as a primary ingredient. One specific product containing just 375 mg of EGCG per dose was linked to liver injury, well below the 800 mg threshold. This likely reflects individual variation: some people’s livers process these compounds poorly, making them vulnerable at lower doses. If you take any supplement with green tea extract, check the label for the EGCG content. Many products don’t disclose it clearly, which is itself a red flag.
Kava
Kava supplements, widely marketed for anxiety and relaxation, have one of the most alarming track records of any herbal product. The World Health Organization reviewed 93 case reports of suspected kava-related liver toxicity. Seven of those patients died, and 14 needed liver transplants. The FDA issued a consumer advisory in 2002, and multiple countries, including France, the UK, Switzerland, Spain, and Canada, have banned or restricted kava products entirely.
One detailed case involved a 45-year-old woman who developed liver failure after taking just 100 mg of kava daily for 52 days, ultimately requiring a transplant. Even traditional kava beverages aren’t exempt: a study of 27 heavy kava drinkers in New Caledonia found evidence of liver injury from the water-based preparations that have been consumed in Pacific Island cultures for centuries. The risk appears highest in women, who made up 79% of the cases the WHO reviewed, with an average age of 45. If you’re using kava for anxiety or sleep, the potential consequences are severe enough to warrant finding an alternative.
Vitamin A
Vitamin A is one of the few vitamins that can directly poison your liver, because it’s fat-soluble and accumulates in liver tissue rather than being flushed out through urine. Taking more than 10,000 mcg (about 33,000 IU) per day on an ongoing basis can cause liver damage, along with hair loss, joint pain, and dry skin. A single massive dose of 200,000 mcg can trigger acute toxicity with nausea, vomiting, and blurred vision.
The risk sneaks up on people who take multiple supplements without checking for overlap. A multivitamin, a skin health formula, and a separate vitamin A capsule can easily stack up past safe levels. Beta-carotene, the form of vitamin A found in carrots and sweet potatoes, does not carry this risk because your body only converts as much as it needs. Preformed vitamin A (listed as retinol or retinyl palmitate on labels) is the form to watch.
Bodybuilding and Performance Supplements
Muscle-building supplements are a persistent source of hidden liver toxins. The FDA reviewed adverse event reports from 2009 to 2016 and found 35 cases of serious liver injury in men ages 20 to 48, all linked to bodybuilding products that contained or were suspected to contain anabolic steroids or steroid-like compounds. Many of these cases involved hospitalization or were classified as life-threatening.
The core issue is that these products often contain undeclared pharmaceutical ingredients, compounds that function like anabolic steroids but aren’t listed on the label, or are listed under unfamiliar chemical names. Steroid-related liver damage is a well-established medical phenomenon. Making things worse, many users stack multiple products at once, which creates unpredictable interactions and makes it impossible to identify which ingredient caused the harm. Any supplement promising rapid muscle gain or using terms like “pro-hormone” or “anabolic” should raise immediate suspicion.
Ashwagandha
Ashwagandha has surged in popularity as a stress and sleep supplement, but a growing number of case reports have linked it to liver injury. A 2023 study published in Pharmaceuticals assessed several cases using a standardized causality tool and identified ashwagandha as an “emerging cause” of herb-induced liver injury. The picture is complicated by the fact that many ashwagandha supplements contain a mix of root and leaf material, and leaves may carry higher concentrations of compounds called withanones that can damage liver cell DNA.
Some research has actually described ashwagandha as liver-protective, which reflects the confusing reality of herbal supplements: the specific plant part used, the extraction method, the dose, and other ingredients in the formula all matter. If you currently take ashwagandha, products made exclusively from root extract appear to carry less risk than those using whole-plant or leaf-based formulations, though no preparation has been proven completely safe for the liver.
Herbal Products With Pyrrolizidine Alkaloids
Some of the most dangerous liver toxins in the supplement world are pyrrolizidine alkaloids, naturally occurring compounds found in comfrey, certain species of ragwort and groundsel, and plants in the heliotrope and crotalaria families. These chemicals damage the small veins inside the liver, causing a condition called veno-occlusive disease where blood flow through the organ gets blocked. In acute cases, this leads to rapid liver cell death. Survivors of acute poisoning can go on to develop cirrhosis over time.
Comfrey is the most commonly encountered source in Western supplements. It was historically sold as a tea and in capsule form for digestive issues and joint pain. Some pyrrolizidine alkaloid-containing plants also cause high blood pressure in the lungs, which can lead to heart failure. Even long-term intake of small quantities is dangerous, because the damage accumulates. Any herbal tea or supplement containing comfrey leaf, comfrey root, or products from the borage family should be avoided entirely.
Usnic Acid in Weight Loss Products
Usnic acid, a compound derived from lichen, has appeared in various weight loss supplements and has a direct, dose-dependent toxic effect on liver cells. It works by disrupting the energy-producing machinery inside cells, essentially shutting down the mitochondria. This triggers a cascade of damage involving unstable molecules called free radicals, destruction of cell membranes, and disruption of calcium balance within cells, all of which lead to cell death. Several cases of severe liver toxicity, including liver failure, have been documented in people taking usnic acid-containing products. It’s sometimes listed on labels as “usnea” or “lichen extract.”
How to Recognize Liver Damage Early
Supplement-related liver injury doesn’t always announce itself with dramatic symptoms. Early signs often mimic everyday complaints: fatigue, loss of appetite, nausea, or a dull ache in the upper right side of your abdomen. More specific warning signs include dark urine (think cola-colored), pale or clay-colored stools, and yellowing of the skin or eyes. Some people develop a rash, fever, or persistent itching.
If you’re taking any of the supplements listed above and notice these symptoms, stopping the product immediately is the single most important step. In many documented cases, liver function returned to normal after the person stopped taking the supplement, sometimes with supportive care. Liver damage from supplements is diagnosed with blood tests that measure enzyme levels, which spike when liver cells are injured or dying. The good news is that the liver has remarkable regenerative ability, but only if the toxic exposure stops before irreversible damage sets in.
Why Supplement Labels Can’t Always Be Trusted
Unlike prescription medications, dietary supplements in the United States don’t require FDA approval before they’re sold. Manufacturers are responsible for their own safety testing, and contamination or mislabeling is common. The FDA’s own analyses have repeatedly found undeclared pharmaceutical ingredients in bodybuilding and weight loss products. Some herbal supplements contain plant parts not listed on the label, or are contaminated with pyrrolizidine alkaloid-producing weeds that grew alongside the intended crop.
Third-party testing certifications (such as USP, NSF, or ConsumerLab seals) provide some reassurance that a product contains what it claims, though they don’t guarantee the ingredients themselves are safe for your liver. If you take supplements regularly, keeping a written record of exactly what you take, including brand names and doses, gives your doctor critical information if liver problems ever arise. Many people take two or three supplements simultaneously without realizing the combination creates risk that neither product carries alone.