Acute Liver Failure (Fulminant Hepatic Failure): Symptoms, Causes, and Emergency Treatment
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 17, 2026
Quick Answer
Acute liver failure is the rapid loss of liver function within days or weeks, usually in someone without prior liver disease. The most common U.S. cause is acetaminophen overdose [3], followed by hepatitis viruses. Warning signs include jaundice, upper right belly swelling and confusion [3]. It is a medical emergency treated in intensive care, sometimes with acetylcysteine or a liver transplant [4].
What the research says
N-acetylcysteine (NAC) improved transplant-free survival in early-stage acute liver failure not caused by acetaminophen. In a double-blind trial of 173 patients, transplant-free survival was 40% with NAC versus 27% with placebo (P = .043), and 52% versus 30% in patients with coma grades I–II. Overall survival at 3 weeks did not differ significantly (70% vs 66%). (Lee et al., Gastroenterology, 2009) [1]
A meta-analysis found the same pattern. Across 5 prospective studies and 672 patients, NAC raised transplant-free survival (55.1% vs 28.1%; RR 0.56; 95% CI 0.33–0.94), while overall survival was not significantly improved (71% vs 59.8%). (Amjad et al., Przegląd Gastroenterologiczny, 2022) [2]
What Is Acute Liver Failure?
Acute liver failure is the loss of liver function that happens quickly — in days or weeks — usually in a person who has no preexisting liver disease. It is most often caused by a hepatitis virus or drugs, such as acetaminophen [3].
It is less common than chronic liver failure, which develops more slowly. Acute liver failure is also known as fulminant hepatic failure [3].
Key fact | What it means |
Speed of onset | Loss of liver function develops in days or weeks [3] |
Typical patient | Often someone with no previous liver disease [3] |
Also called | Fulminant hepatic failure [3] |
Severity | A medical emergency requiring hospitalization [3] |
Most common U.S. cause | Acetaminophen (Tylenol) overdose [3] |
Possible outcomes | Sometimes reversible with treatment; often requires a liver transplant |
Acute liver failure can cause serious complications, including bleeding and increased pressure in the brain. Because of these dangers, it requires hospitalization as soon as it is recognized. Depending on the cause, it can sometimes be reversed with treatment. In many situations, though, a liver transplant may be the only cure [3].
What are the symptoms of acute liver failure?
Acute liver failure symptoms can come on fast in someone who seemed healthy, and yellowing of the eyes or skin, upper belly tenderness or mental changes need medical attention right away. Symptoms of acute liver failure may include:
Symptom | What you might notice |
Jaundice | Yellowing of the skin and eyeballs [3] |
Abdominal pain | Pain in the upper right belly area [3] |
Ascites | A swollen belly [3] |
Nausea and vomiting | Feeling sick, sometimes with vomiting [3] |
Malaise | A general sense of feeling unwell [3] |
Disorientation or confusion | Changes in mental state [3] |
Sleepiness | Increased drowsiness [3] |
Odor changes | Breath with a musty or sweet odor [3] |
Tremors | Shaking or tremor [3] |
When to See a Doctor
Acute liver failure can develop quickly in an otherwise healthy person, and it is life-threatening [3].
Seek medical attention right away if you or someone you know suddenly develops any of the following:
Do not wait to see whether the symptoms pass. Speed matters because early treatment may prevent full liver failure or reduce complications.
What Causes Acute Liver Failure?
Acute liver failure occurs when liver cells are seriously damaged and are no longer able to function. There are many possible causes.
Acetaminophen overdose is the most common cause of acute liver failure in the United States. Outside of the United States, acetaminophen is known as paracetamol. Acute liver failure can happen after one very large dose of acetaminophen, or after higher-than-recommended doses every day for several days [3].
If you or someone you know has taken an overdose of acetaminophen, seek medical attention as quickly as possible. Treatment may prevent liver failure. Don't wait for the symptoms of liver failure [3].
Cause | Details |
Acetaminophen overdose | Most common cause in the U.S.; from one very large dose or repeated above-recommended doses [3] |
Hepatitis viruses | Hepatitis A, B, and E increase risk [3] |
Other viruses | Epstein-Barr virus, cytomegalovirus, herpes simplex virus [3] |
Prescription medicines | Antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), anticonvulsants [3] |
Herbal supplements | Kava, ephedra, skullcap, pennyroyal [3] |
Toxins | Amanita phalloides wild mushroom; carbon tetrachloride (found in refrigerants and solvents for waxes and varnishes) [3] |
Autoimmune disease | Autoimmune hepatitis, where the immune system attacks liver cells [3] |
Vein diseases | Budd-Chiari syndrome blocks veins of the liver [3] |
Metabolic diseases | Rare conditions such as Wilson's disease and acute fatty liver of pregnancy [3] |
Cancer | Cancer that begins in or spreads to the liver [3] |
Shock or sepsis | Overwhelming infection and shock severely reduce blood flow to the liver [3] |
Heat stroke | Extreme physical activity in a hot environment [3] |
Some cases of acute liver failure have no obvious cause [3].
What are the risk factors for acute liver failure?
Certain factors make acute liver failure more likely.
What complications can acute liver failure cause?
Acute liver failure often causes complications, and managing them is a major part of treatment.
Complication | What happens |
Cerebral edema | Too much fluid in the brain causes pressure to build up, leading to disorientation, severe mental confusion, and seizures [3] |
Bleeding and bleeding disorders | A failing liver cannot make enough clotting factors; bleeding in the gastrointestinal tract is common and may be difficult to control [3] |
Infections | Higher risk of infections, particularly in the blood and in the respiratory and urinary tracts [3] |
Kidney failure | Often occurs after liver failure, especially with acetaminophen overdose, which damages both the liver and the kidneys [3] |
How can you prevent acute liver failure?
Reduce your risk of acute liver failure by taking care of your liver.
Prevention step | What to do |
Follow medicine instructions | Check the package insert for the recommended dose and don't exceed it; if you have liver disease, ask your healthcare team whether any amount of acetaminophen is safe [3] |
Report all medicines | Tell your healthcare team about every medicine, including nonprescription and herbal products [3] |
Limit alcohol | Drink in moderation — up to one drink a day for women, up to two a day for men [3] |
Avoid risky behavior | Get help for illicit intravenous drug use, don't share needles, use condoms, choose clean tattoo and piercing shops, don't smoke [3] |
Get vaccinated | Hepatitis B vaccine (and hepatitis A vaccine) if you have chronic liver disease, a history of hepatitis, or increased risk [3] |
Avoid blood contact | Prevent accidental needle sticks, improper cleanup of blood or body fluids, and avoid sharing razors or toothbrushes [3] |
Don't eat wild mushrooms | It is difficult to tell poisonous mushrooms from safe ones [3] |
Use sprays safely | Ventilate the room or wear a mask with aerosol cleaners, insecticides, fungicides, and paint; follow product instructions [3] |
Protect your skin | Wear gloves, long sleeves, a hat, and a mask when using insecticides and other toxic chemicals [3] |
Maintain a healthy weight | Obesity can cause metabolic dysfunction-associated steatotic liver disease (MASLD, formerly NAFLD), which may lead to serious liver damage [3] |
How is acute liver failure diagnosed?
Acute liver failure is diagnosed with several tests and procedures, and a transjugular liver biopsy through a neck vein may be used because a standard biopsy carries a bleeding risk [4].
Test | What it shows |
Blood tests | Show how well the liver works; the prothrombin time test measures how long it takes blood to clot — with acute liver failure, blood doesn't clot as quickly as it should [4] |
Ultrasound | Looks at the liver; may show damage and help find the cause [4] |
CT or MRI scan | Abdominal computerized tomography or magnetic resonance imaging looks at the liver and blood vessels; used to find causes such as Budd-Chiari syndrome or tumors when ultrasound doesn't find the problem [4] |
Liver biopsy | A small piece of liver tissue is removed to discover why the liver is failing [4] |
Because people with acute liver failure are at risk of bleeding during a standard biopsy, a transjugular liver biopsy may be performed instead. This procedure involves making a tiny incision on the right side of the neck. A thin tube called a catheter is inserted into a neck vein, guided through the heart, and into a vein exiting the liver. A needle is then threaded through the catheter to retrieve the liver tissue sample.
How is acute liver failure treated?
People with acute liver failure often receive treatment in the intensive care unit of a hospital in a facility that can perform a liver transplant, if necessary. A healthcare professional may try to treat the liver damage itself, but in many cases treatment involves controlling complications and giving the liver time to heal [4].
Treatment | How it works |
Medicines to reverse poisoning | Acetaminophen overdose is treated with a medicine called acetylcysteine; it may also help other causes. Mushroom and other poisonings may be treated with medicines that reverse the toxin's effects and may reduce liver damage [4] |
Liver transplant | When acute liver failure can't be reversed, the only treatment may be a liver transplant — the damaged liver is removed and replaced with a healthy donor liver [4] |
Reducing brain pressure | Medicines can help reduce the fluid buildup in the brain caused by cerebral edema [4] |
Infection screening | Blood and urine samples are tested periodically; medicines treat any infection found [4] |
Preventing severe bleeding | Medicines reduce bleeding risk; tests find the source of major blood loss; blood transfusions may be needed [4] |
Nutritional support | Supplements treat nutritional deficiencies if you are unable to eat [4] |
Future Treatments Under Study
Scientists continue to research new treatments, especially those that could reduce or delay the need for a liver transplant. All of the following are experimental and may not yet be available:
Experimental treatment | Concept and status |
Artificial hepatic assist devices | A machine does the liver's job, like dialysis for kidneys; one extracorporeal liver support system (high-volume plasma exchange) helped some people survive without a transplant in a controlled trial, but more study is needed |
Hepatocyte transplantation | Transplanting only liver cells, not the whole organ, may temporarily delay the need for a transplant and could lead to complete recovery; limited by a shortage of good-quality donor livers |
Auxiliary liver transplantation | A small piece of your liver is removed and replaced with a similarly sized graft, letting your own liver regenerate without immunosuppressant drugs; difficult procedure that needs more research [4] |
Xenotransplantation | Replacing the human liver with a liver from an animal source (such as a pig); early attempts decades ago were disappointing, but advances in immune and transplant medicine have renewed interest [4] |
How should you prepare for an appointment about acute liver failure?
If a healthcare professional suspects you have acute liver failure, you'll likely be admitted to a hospital for treatment. Most people with acute liver failure are treated in an intensive care unit [4].
Questions you can ask your care team:
What caused my acute liver failure?
Can it be reversed?
If it can be reversed, can my liver completely heal?
What are the treatments?
Will I need a liver transplant?
Does this hospital have a liver transplant unit?
Should I transfer to a hospital that performs liver transplants?
What your care team will ask you or your family (to help find the cause):
When did symptoms begin?
What prescription medicines do you take?
What over-the-counter medicines do you take?
What herbal supplements do you take?
Do you use illegal drugs?
Have you had liver problems in the past?
Have you been diagnosed with hepatitis or jaundice?
Do you have a history of depression or suicidal thoughts?
How much alcohol do you drink?
Have you recently started taking new medicines?
Do you take acetaminophen (Tylenol, others)? How much?
Do liver problems run in your family?
Conclusion
Acute liver failure is a rare, fast-moving, and life-threatening condition in which a liver that was previously healthy stops working within days or weeks. In the United States, the most common cause is acetaminophen overdose, but viruses, prescription medicines, herbal supplements, toxins, and metabolic diseases can all trigger it [3]. The danger comes from complications such as brain swelling, uncontrolled bleeding, infection, and kidney failure [3].
Because this condition is a medical emergency, the single most important action is to seek care immediately when warning signs appear — especially sudden jaundice, upper-belly tenderness, or unusual changes in mental state. Early treatment with medicines like acetylcysteine can sometimes reverse the damage, and liver transplant centers stand ready when they cannot.
If you found this guide helpful, share it with someone who takes daily medicines or supplements — and review the safe-dose instructions on every acetaminophen-containing product in your medicine cabinet today.
Frequently Asked Questions
What is acute liver failure? Acute liver failure is the rapid loss of liver function, developing in days or weeks, usually in someone with no preexisting liver disease. It is a medical emergency that requires hospitalization and is most often caused by acetaminophen overdose or a hepatitis virus.
What is the most common cause of acute liver failure in the U.S.? Taking too much acetaminophen (Tylenol) is the most common cause in the United States. It can result from one very large dose or from repeated doses above the recommendation over several days.
What are the first signs of acute liver failure? Early signs include yellowing of the skin and eyes (jaundice), pain in the upper right belly, a swollen belly, nausea, vomiting, a general feeling of unwellness, and later disorientation, sleepiness, musty-sweet-smelling breath, and tremors.
Is acute liver failure reversible? Depending on the cause, acute liver failure can sometimes be reversed with treatment. In many situations, however, a liver transplant may be the only cure.
Why is acetaminophen overdose so dangerous for the liver? A single very large dose of acetaminophen, or higher-than-recommended daily doses over several days, can seriously damage liver cells. If an overdose is taken, seek medical attention immediately — treatment may prevent liver failure, so don't wait for symptoms.
How is acute liver failure diagnosed? Diagnosis includes blood tests (including a prothrombin time test to measure clotting), an ultrasound of the liver, CT or MRI scans to check for causes such as Budd-Chiari syndrome or tumors, and sometimes a liver biopsy. A transjugular biopsy through a neck vein may be used to reduce bleeding risk.
What is fulminant hepatic failure? Fulminant hepatic failure is another name for acute liver failure — rapid loss of liver function in someone without prior liver disease, often accompanied by serious complications like brain pressure and bleeding.
Can acute liver failure affect the brain? Yes. Excess fluid in the brain, called cerebral edema, builds pressure that can cause disorientation, severe mental confusion, and seizures. Medicines can help reduce this fluid buildup.
What is the treatment for acute liver failure? Treatment usually happens in an intensive care unit at a hospital able to perform a liver transplant. It may include acetylcysteine to reverse acetaminophen poisoning, medicines for brain pressure, infection screening, bleeding prevention, nutritional support, or a liver transplant when the damage cannot be reversed.
Who is at highest risk for acute liver failure? A majority of people affected are female. Having an underlying illness — such as viral hepatitis, a metabolic disease, autoimmune disease, or cancer — also increases risk.
How can I prevent acute liver failure? Follow medication instructions and never exceed the recommended acetaminophen dose, tell your healthcare team about all medicines and supplements, drink alcohol in moderation, get vaccinated against hepatitis, avoid wild mushrooms and toxic chemical exposure, and maintain a healthy weight.
Trusted External Resources
Related Reading
Learn more in our guide to Living Donor Liver Transplant: Who Can Donate, Surgery, Risks and Recovery.
MELD Score: What It Measures, How to Read It and What It Means for a Liver Transplant explains the score used to rate liver disease severity and how urgently a liver transplant is needed.
References
Lee WM, Hynan LS, Rossaro L, et al. Intravenous N-acetylcysteine improves transplant-free survival in early stage non-acetaminophen acute liver failure. Gastroenterology. 2009;137(3):856-864. PMID: 19524577. https://doi.org/10.1053/j.gastro.2009.06.006
Amjad W, Thuluvath P, Mansoor M, et al. N-acetylcysteine in non-acetaminophen-induced acute liver failure: a systematic review and meta-analysis of prospective studies. Przegląd Gastroenterologiczny. 2022;17(1):9-16. PMID: 35371352. https://doi.org/10.5114/pg.2021.107797
Mayo Clinic Staff. Acute liver failure — Symptoms and causes. Mayo Clinic. Oct. 15, 2024. https://www.mayoclinic.org/diseases-conditions/acute-liver-failure/symptoms-causes/syc-20352863
Mayo Clinic Staff. Acute liver failure — Diagnosis and treatment. Mayo Clinic. Oct. 15, 2024. https://www.mayoclinic.org/diseases-conditions/acute-liver-failure/diagnosis-treatment/drc-20352868
American Liver Foundation. 13 Ways to a Healthy Liver. American Liver Foundation. Last updated August 14, 2025. https://liverfoundation.org/resource-center/blog/healthy-liver-tips/
National Institute of Diabetes and Digestive and Kidney Diseases. Liver Disease. NIDDK. Accessed October 30, 2026. https://www.niddk.nih.gov/health-information/liver-disease
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