Pre-workout supplements can cause liver damage, though the risk depends far more on specific ingredients and individual biology than on the product category itself. Published case reports range from mild enzyme elevations that resolve on their own to acute liver failure severe enough to require a transplant. The ingredients that show up most often in these cases are concentrated green tea extract, high-dose niacin, and lesser-known stimulants like theacrine, while staple ingredients such as creatine and beta-alanine have a reassuring safety record for the liver. What makes the picture complicated is that many pre-workout formulas hide their ingredient doses behind proprietary blends, and some people carry genetic variants that make them unusually susceptible to drug- and supplement-induced liver injury.
Documented Cases of Pre-Workout Liver Injury
The medical literature includes several reports of otherwise healthy young adults developing serious liver problems after using pre-workout products. In one published case, a woman who used the pre-workout supplement OxyShred for nine weeks was admitted to the hospital with fatigue, vomiting, and jaundice. Her liver injury progressed to full-blown liver failure, and she ultimately needed a liver transplant.1World Journal of Hepatology. Acute liver failure linked to OxyShred pre-workout supplement: A case report and review of literature In another case, a previously healthy young adult developed a cholestatic pattern of liver injury after taking creatine, whey protein powder, and “Mr. Hyde” pre-workout. Investigators suspected an ingredient called theacrine, which in animal studies caused liver cell death at high concentrations. The caffeine also present in the product may have worsened the problem by increasing how much theacrine the body absorbs.2PubMed Central. Herbal and dietary supplement induced liver injury: Highlights from the recent literature
These are not isolated curiosities. A broader review of supplement-induced liver injury found that the damage can take several forms: direct hepatocellular injury (damage to liver cells themselves), prolonged cholestasis (where bile flow is blocked), and in the worst outcomes, acute liver failure requiring transplantation.3PubMed Central. Supplement-Induced Liver Injury The common thread in these cases is that patients were young, had no prior liver disease, and did not suspect their supplement could be the cause.
The Ingredients Most Linked to Liver Harm
Not every ingredient in a pre-workout carries meaningful liver risk. The ones that turn up most consistently in hepatotoxicity reports are green tea extract, high-dose niacin, and certain less-studied stimulant compounds.
Green Tea Extract
Green tea extract (GTE) is added to many pre-workouts and fat burners for its purported fat-oxidation and energy benefits. The catechin EGCG appears to be the compound responsible for the liver toxicity seen in case reports. A comprehensive review by the United States Pharmacopeia found that published adverse event reports linked hepatotoxicity to EGCG intake amounts ranging from about 140 mg to roughly 1,000 mg per day, with substantial variation from person to person in who gets hurt. Laboratory studies on rat liver cells showed that EGCG exposure at moderate concentrations over 24 hours was enough to injure cells and reduce liver function.4Toxicology Reports. United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts Many pre-workout labels list GTE without specifying the EGCG content, making it hard to know whether a given product falls in a risky range.
High-Dose Niacin
Niacin (vitamin B3) shows up in some pre-workout and performance formulas, often as an extended-release form marketed for its vasodilatory “flush.” At self-directed high doses, extended-release niacin can cause severe liver damage. One published case described a patient who took large quantities of extended-release niacin on his own and was hospitalized with acute decompensated cirrhosis. He died on day 16 of hospitalization.5Journal of Investigative Medicine High Impact Case Reports. Cholestatic Drug-Induced Liver Injury in a Patient Taking High-Dose Niacin for Hyperlipidemia The extended-release formulation seems to carry more hepatotoxic potential than immediate-release niacin, and the risk rises with both dose and duration.
Theacrine and Caffeine Interactions
Theacrine is a stimulant compound structurally similar to caffeine that appears in some pre-workout products. On its own at moderate doses, theacrine is not well studied in humans for liver safety. But rats exposed to high concentrations developed liver cell death. The concerning twist is that caffeine, which is present in virtually every pre-workout formula, increases how much theacrine gets absorbed, potentially pushing blood concentrations into a hepatotoxic range.2PubMed Central. Herbal and dietary supplement induced liver injury: Highlights from the recent literature This kind of ingredient interaction is one of the hardest risks for consumers to anticipate on their own.
Core Ingredients That Appear Safe for the Liver
The most widely used pre-workout ingredients have a more encouraging track record. Creatine, beta-alanine, and standard multi-ingredient formulas at labeled doses have all been studied specifically for liver effects, and the findings are reassuring.
A large population-based analysis found that consuming 2 grams or more of creatine daily did not significantly increase the risk of liver fibrosis, cirrhosis, or fatty liver disease compared to consuming less than 1 gram, even after adjusting for factors like body weight, alcohol use, and overall calorie intake.6PubMed Central. Creatine consumption and liver disease manifestations in individuals aged 12 years and over This is relevant because creatine gets singled out in gym culture as a potential liver stressor, and the data simply does not support that concern at normal supplementation doses.
Beta-alanine, another common pre-workout staple, has also been evaluated. A systematic review and meta-analysis found that it caused a small increase in one liver enzyme marker (ALT), but the average values stayed well within normal clinical reference ranges. The authors concluded that beta-alanine supplementation at the doses used in available research does not adversely affect people who take it.7PubMed Central. A Systematic Risk Assessment and Meta-Analysis on the Use of Oral β-Alanine Supplementation
A controlled trial of a multi-ingredient pre-workout supplement taken daily for 28 days at both single-serving and double-serving doses found no clinically significant changes in heart, liver, or kidney function markers.8Food & Nutrition Research. A multi-ingredient, pre-workout supplement is apparently safe in healthy males and females That trial was short, and “no clinically significant changes” in a healthy population over four weeks does not guarantee safety after months of daily use. But it does suggest that a well-formulated product at recommended doses is unlikely to cause acute liver harm in people who are otherwise healthy.
The Proprietary Blend Problem
One of the biggest practical risks with pre-workout supplements is not knowing what you are actually taking. Many products list a “proprietary blend” on the label, which groups several ingredients under one combined weight without disclosing the individual amounts. A survey of regular pre-workout consumers found that this makes it extremely difficult to figure out which ingredient is responsible when side effects occur. Researchers have recommended that consumers and healthcare professionals prioritize products that do not contain proprietary blends with undisclosed ingredients or amounts, specifically so people can identify what they are ingesting and trace any problems back to a cause.9PubMed Central. Common Habits, Adverse Events, and Opinions Regarding Pre-Workout Supplement Use Among Regular Consumers
Beyond unclear labeling, outright contamination and adulteration remain a problem. Dietary supplements in the United States do not require pre-market approval the way drugs do, and safety issues with adulteration and contamination persist, particularly with bodybuilding and performance-enhancement products.10PubMed Central. Current regulatory guidelines and resources to support research of dietary supplements in the United States Some over-the-counter supplements have been found to contain undeclared anabolic androgenic steroids, which carry their own well-documented liver toxicity.11American Journal of Gastroenterology. Hepatotoxicity Associated With Anabolic Androgenic Steroids Present in Over-the-Counter Supplements: A Case Series A product may be “just a pre-workout” on the label and something far more dangerous in the tub.
Why Some People React While Others Do Not
One of the frustrating aspects of supplement-induced liver injury is its unpredictability. Two people can take the same product at the same dose, and only one gets sick. A growing body of genetic research helps explain why. Certain variants in HLA genes, which are part of the immune system, appear to predispose people to idiosyncratic drug-induced liver injury. In these reactions, a supplement ingredient or its metabolite binds to a protein in the body and creates a new molecular structure that the immune system treats as foreign, triggering an attack on liver cells.12PubMed Central. Human Leukocyte Antigen (HLA) Signatures and Idiosyncratic Drug-Induced Liver Injury
Most of the HLA associations studied so far involve prescription drugs rather than supplements, but the underlying mechanism applies to any foreign substance the liver processes. Genome-wide studies have identified several HLA alleles and a few non-HLA genes that raise susceptibility, and it is likely that multiple genetic factors combine with other variables like drug dose and overall health to determine who gets hurt.13PubMed Central. Genetics of drug-induced liver injury: Current knowledge and future prospects This means there is no simple blood test you can take to find out if a particular pre-workout is safe for you specifically. The genetic landscape is too complex and too poorly mapped for supplement ingredients in particular.
How Severe the Damage Can Get
At the mild end, supplement-induced liver injury shows up as elevated liver enzymes on routine blood work, sometimes with fatigue and nausea, and resolves once the product is stopped. At the severe end, it can progress to acute liver failure requiring emergency transplantation. Data from multiple international liver injury registries found that acute liver failure occurred in roughly 6 to 17 percent of dietary supplement-related liver injury cases, depending on the registry.2PubMed Central. Herbal and dietary supplement induced liver injury: Highlights from the recent literature Those numbers cover all herbal and dietary supplements, not pre-workouts alone, but pre-workout ingredients like green tea extract are among the more frequently implicated.
The trend line is not encouraging. An analysis of patients waitlisted for liver transplants due to herbal and dietary supplement injuries found that over 70 percent of cases occurred in the decade between 2010 and 2020, compared to the prior 15 years combined.14PubMed Central. Liver Transplantation for Acute Liver Injury in Asians Is More Likely Due to Herbal and Dietary Supplements This likely reflects both a rise in supplement use and improved recognition of supplements as a cause of liver failure, but either way, the clinical burden is growing.
How Doctors Determine Whether a Supplement Caused the Injury
Pinning a liver injury on a specific supplement is harder than it sounds. There is no single blood test or biopsy finding that says “this was caused by a supplement.” Doctors use a structured scoring tool called RUCAM (Roussel Uclaf Causality Assessment Method), which walks through the timeline of exposure, the pattern of enzyme elevations, whether other causes have been excluded, and what happened after the supplement was stopped. Each element gets a score, and the total determines how likely it is that the supplement was the culprit.15PubMed Central. RUCAM in Drug and Herb Induced Liver Injury: The Update Since the mid-1990s, nearly 96,000 suspected cases of drug- and herb-induced liver injury have been assessed using RUCAM worldwide, making it the most widely used causality assessment tool for this purpose.16PubMed Central. Idiosyncratic Drug-Induced Liver Injury (DILI) and Herb-Induced Liver Injury (HILI): Diagnostic Algorithm Based on the Quantitative Roussel Uclaf Causality Assessment Method (RUCAM)
One practical takeaway: if you develop unexplained fatigue, nausea, dark urine, or yellowing of the skin or eyes while taking a pre-workout, bring the product container to your doctor. The ingredient list is essential for a RUCAM assessment, and proprietary blends make the process harder. Having the actual product speeds up the diagnostic work and may help identify the offending ingredient for future avoidance.
When Elevated Liver Enzymes Are Not Actually Liver Damage
If you are someone who gets regular blood work and takes pre-workout supplements, there is an important wrinkle worth knowing about. Intense exercise by itself can cause liver enzyme levels to spike in ways that look alarming on paper. A study of healthy men found that five out of eight common clinical chemistry markers, including AST and ALT (the two enzymes most commonly used to screen for liver injury), increased significantly after strenuous exercise and stayed elevated for at least seven days.17PubMed Central. Muscular exercise can cause highly pathological liver function tests in healthy men The elevations come from skeletal muscle damage, not the liver, but the blood tests cannot tell the difference on their own.
This matters for pre-workout users because both the exercise and the supplement can independently raise the same markers. A doctor who does not know about recent heavy training might attribute the elevation to the supplement, and someone who recently trained hard might dismiss abnormal results as “just from the gym” when the supplement truly is the problem. If blood work shows elevated liver enzymes, the timing relative to your last hard workout and the specific pattern of which enzymes are elevated both matter for sorting out the cause. Markers like GGT and bilirubin tend to stay normal after exercise but rise in genuine liver injury, which can help distinguish the two.
Dry Scooping and Other Misuse Patterns
The way people take pre-workouts adds another layer of risk. “Dry scooping,” the practice of dumping a scoop of undiluted powder directly into your mouth without mixing it in water, took off on social media and remains popular despite its dangers. An analysis of pre-workout content on TikTok found that 86 percent of individuals shown in videos were depicted engaging in improper use, including dry scooping.18PubMed Central. Acute myocardial infarction following “dry scooping” of a pre-workout supplement in a healthy young man of African origin: A case report Dry scooping delivers the entire dose of stimulants and other active ingredients in a concentrated bolus, which raises peak blood levels faster than mixing the powder in water as directed. The cardiovascular risks (heart palpitations, blood pressure spikes, and in at least one published case, a heart attack in a healthy young man) tend to get the most attention, but the same rapid-absorption logic applies to hepatotoxic ingredients like EGCG. A higher peak blood concentration means a higher peak concentration reaching the liver.
Artificial Sweeteners and the Gut-Liver Connection
Most pre-workout supplements are flavored with artificial sweeteners like sucralose, acesulfame potassium, or saccharin. These are generally considered safe in the amounts used, but emerging animal research raises questions about indirect effects on the liver through the gut. Mice fed saccharin at a dose equivalent to the FDA-approved acceptable daily intake for humans for six months showed increased markers of liver inflammation, along with measurable changes in the composition of their gut bacteria.19PubMed Central. Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials The altered bacterial genera were associated with the observed liver inflammation, suggesting a pathway from the gut microbiome to the liver.
This research is still in early stages, conducted in mice rather than humans, and the relevance to a single scoop of pre-workout consumed a few times a week is unclear. But it does point to a broader theme in supplement safety research: the effects of individual ingredients are studied mostly in isolation, while real-world products deliver a cocktail of active compounds, sweeteners, flavoring agents, and fillers. How all of these interact inside the body over months of daily use is territory that clinical science has barely begun to map.