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Health condition · Clinically reviewed

Acute liver failure, King's College Criteria, NAC and when transplant is the answer.

A rare but life-threatening loss of liver function within days to weeks. Rapid recognition, an urgent liver unit call and a clear decision on transplant listing change outcomes.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against BASL, EASL, AASLD and peer-reviewed hepatology sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including King's College Criteria, NAC in non-paracetamol ALF, and transplant thresholds.

Key facts

Acute liver failure at a glance.

The essentials, in plain English - what it is, how it presents, and how UK liver units decide who needs a transplant.

  • What it is

    Rapid loss of liver function within days to weeks in a previously healthy liver, with coagulopathy (INR at or above 1.5) and any grade of encephalopathy.

  • How rare it is

    Uncommon but life-threatening. Around 5 to 10 cases per million adults per year in the UK, with paracetamol the leading cause.

  • Most common UK cause

    Paracetamol overdose, both intentional and accidental (staggered or therapeutic-misadventure) is by far the most common cause in the UK.

  • Time course

    Hyperacute (within 7 days), acute (8 to 28 days) or subacute (5 to 12 weeks) from jaundice to encephalopathy.

  • Where it is treated

    Any suspected ALF is a hepatology emergency and needs urgent discussion with a specialist liver unit and intensive care.

  • The main decision

    Whether the patient meets King's College Criteria for super-urgent liver transplant listing, alongside full supportive care.

Why this guide matters

Time matters more than almost anything else.

Acute liver failure is uncommon but moves quickly. The three points below shape everything else on this page.

  • Early recognition saves lives

    New coagulopathy with any encephalopathy in someone without chronic liver disease is ALF until proven otherwise. Call the liver unit before waiting for full criteria.

  • NAC is not just for paracetamol

    Modern evidence supports N-acetylcysteine in early non-paracetamol ALF too. Most UK units now use it in almost all suspected ALF.

  • King's College Criteria drive listing

    A structured, validated way to decide who benefits from super-urgent transplant, with separate thresholds for paracetamol and non-paracetamol causes.

How the diagnosis is made

From first bloods to a transplant-unit call.

The steps a UK acute-medicine team or hepatologist will normally follow, in order - so families know what to expect and why.

  1. 01

    Recognising

    Recognise ALF early

    A new coagulopathy (INR at or above 1.5) with any encephalopathy in someone without known chronic liver disease is ALF until proven otherwise.

  2. 02

    Recognising

    Full drug and exposure history

    Every medicine, herbal, supplement and recreational drug, mushroom ingestion, alcohol, occupational exposures and travel history.

  3. 03

    Recognising

    Bloods and gases

    INR, PT, LFTs, bilirubin, ammonia, creatinine, urea, glucose, lactate, arterial blood gas, paracetamol level and full blood count.

  4. 04

    Investigating

    Aetiology screen

    Viral serology (A, B, C, E and HSV), autoimmune antibodies, caeruloplasmin and 24-hour copper for Wilson's, and beta-hCG in women of childbearing age.

  5. 05

    Investigating

    Imaging

    Liver ultrasound with Doppler to look at hepatic and portal vein flow (excluding Budd-Chiari) and to assess parenchyma.

  6. 06

    Deciding

    Urgent liver unit referral

    Discuss every suspected ALF with a specialist transplant centre early, before encephalopathy worsens and transfer becomes harder.

  7. 07

    Deciding

    Apply King's College Criteria

    Used to decide who needs super-urgent transplant listing, with separate thresholds for paracetamol and non-paracetamol causes.

Typical timeline: from admission to a transplant-unit decision within hours, not days.

Symptoms

What acute liver failure actually looks like.

The features that turn a viral-feeling illness or an overdose into a hepatology emergency - and the ones that mean intensive care, immediately.

  • Jaundice

    Yellowing of the sclerae and skin as bilirubin rises, often the first visible sign that something is very wrong.

  • Nausea and vomiting

    Early non-specific symptoms that are easy to attribute to a viral illness, particularly after a paracetamol overdose.

  • Right upper quadrant pain

    Discomfort or tenderness under the right ribs as the liver becomes acutely inflamed.

  • Coagulopathy and bruising

    Easy bruising, nosebleeds or bleeding gums as clotting factors fall and INR rises above 1.5.

  • Encephalopathy

    Confusion, altered sleep, personality change, drowsiness or coma. Any change in consciousness is a red flag.

  • Asterixis (liver flap)

    Coarse flapping tremor of the outstretched hands, an early bedside sign of hepatic encephalopathy.

  • Hypoglycaemia

    The failing liver stops producing glucose, so low blood sugar is common and needs early correction.

  • Red flag - cerebral oedema

    Rapidly worsening encephalopathy, pupillary changes or hypertension can signal raised intracranial pressure. An immediate ICU emergency.

Treatment

How acute liver failure is treated in the UK.

N-acetylcysteine early, full organ support in intensive care, aggressive neuroprotection - and a low threshold for super-urgent transplant listing.

  • N-acetylcysteine (NAC)

    The antidote for paracetamol-induced ALF. Evidence also supports NAC in early non-paracetamol ALF, improving transplant-free survival in low-grade encephalopathy.

  • Intensive care admission

    Airway, breathing and circulation support in a critical-care setting with hepatology and transplant-unit involvement from the outset.

  • Neuroprotection

    Target-controlled sedation, head-up tilt, hypertonic saline or mannitol for raised intracranial pressure, and careful management of ammonia and sodium.

  • Renal support

    Continuous renal replacement therapy for acute kidney injury, which also helps clear ammonia and control acidosis and fluid balance.

  • Cardiovascular and respiratory support

    Vasopressors for shock, mechanical ventilation for grade III to IV encephalopathy, and lung-protective settings throughout.

  • Infection prophylaxis and treatment

    A low threshold for broad-spectrum antibiotics and antifungals, since sepsis is a leading cause of death and can preclude transplantation.

  • Correction of coagulopathy

    Not corrected routinely (INR is a prognostic marker), but blood products are given for active bleeding or before invasive procedures.

  • Super-urgent liver transplant

    For patients meeting King's College Criteria. Post-transplant 1-year survival is around 80% and 5-year survival 70 to 80% in modern UK series.

What this guide is based on

The sources behind every claim on this page.

UK and international hepatology guidance and MHRA prescribing advice, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

If you or someone with you is unwell after an overdose or has new confusion with jaundice, call 999 or go to A&E immediately.

  • European Association for the Study of the Liver (EASL). Clinical Practice Guidelines on the management of acute (fulminant) liver failure.

  • British Association for the Study of the Liver (BASL) / British Society of Gastroenterology. Guidance on acute liver failure.

  • AASLD. Position paper on the management of acute liver failure.

  • NHS Blood and Transplant. Liver transplantation - selection criteria and organ allocation policies (POL195).

  • MHRA. Paracetamol overdose - updated treatment nomogram and NAC guidance.

Red flags

When to escalate immediately.

The features that mean an immediate liver-unit call, intensive care, or super-urgent transplant assessment.

  • Any encephalopathy with coagulopathy

    New confusion or drowsiness in someone with an INR at or above 1.5 and no known chronic liver disease is ALF until proven otherwise. Call the liver unit.

  • Paracetamol overdose meeting King's

    Arterial pH below 7.3 after resuscitation, or INR above 6.5 with creatinine above 300 micromol/L and grade III to IV encephalopathy. Super-urgent transplant listing.

  • Non-paracetamol King's criteria

    INR above 6.5, or any 3 of: age under 10 or over 40, non-A non-B hepatitis or drug reaction, jaundice more than 7 days before encephalopathy, INR above 3.5, bilirubin above 300.

  • Rising lactate or acidosis

    A persistently rising arterial lactate or unresolving metabolic acidosis after fluid resuscitation is a strong marker of poor prognosis.

  • Cerebral oedema signs

    Sustained hypertension, bradycardia, pupillary changes or seizures. Treat as raised intracranial pressure and involve neurointensive care.

  • Hypoglycaemia

    The failing liver cannot maintain glucose. Check capillary glucose frequently and treat aggressively with dextrose infusion.

  • Sepsis

    A rapid deterioration, new fever or unexplained shock can be the first sign of bacterial or fungal sepsis. A low threshold for cultures and antimicrobials.

  • Wilson's disease presentation

    A young patient with ALF, haemolysis, low alkaline phosphatase and a high bilirubin-to-ALP ratio. Almost always needs transplantation.

  • Pregnancy-related ALF

    HELLP or acute fatty liver of pregnancy in the third trimester. Delivery is the definitive treatment and needs immediate obstetric input.

Living with it

After the crisis, a long road that can go well.

Whether recovery happens with medical support or with transplantation, the months that follow shape the long-term outcome. Four priorities matter most.

A quiet reminder

Recovery is measured in months, not days.

Fatigue, mood changes and cognitive slowing after ALF are common and gradually improve. Steady follow-up beats heroic milestones.

  1. 01 Recovery

    Hepatology follow-up

    Whether after medical recovery or transplant, structured follow-up in a liver clinic tracks liver function, immunosuppression and complications.

  2. 02 Medicines

    A careful medication review

    Every future prescription and over-the-counter medicine needs to be checked. Paracetamol may still be safe at reduced doses, but the whole list should be reviewed.

  3. 03 Alcohol

    Avoid alcohol

    Complete abstinence is usually advised, particularly in the first year and lifelong after transplant.

  4. 04 Mental health

    Psychological support

    After a paracetamol overdose or intensive care stay, structured mental-health support and safety planning are as important as the physical follow-up.

Frequently asked

Everything we get asked about acute liver failure.

Quick answers on causes, King's College Criteria, NAC and transplantation.

  • What is acute liver failure?

    Acute liver failure (ALF) is the rapid loss of liver function within days to weeks in someone without pre-existing liver disease, defined by a coagulopathy (INR at or above 1.5) and any grade of hepatic encephalopathy. It is rare but life-threatening and always managed in a specialist liver unit.

  • What is the most common cause of ALF in the UK?

    Paracetamol overdose is by far the leading cause in the UK, whether from a single large intentional overdose or a staggered therapeutic-misadventure pattern. Other causes include viral hepatitis (A, B and E), idiosyncratic drug reactions, autoimmune hepatitis, Wilson's disease, Budd-Chiari syndrome, ischaemic hepatitis, sepsis and pregnancy-related liver disease (HELLP and acute fatty liver of pregnancy).

  • What are the King's College Criteria?

    The King's College Criteria are the UK standard for identifying ALF patients who need super-urgent liver transplantation. For paracetamol ALF: arterial pH below 7.3 after fluid resuscitation, or the combination of INR above 6.5, creatinine above 300 micromol/L and grade III to IV encephalopathy. For non-paracetamol ALF: INR above 6.5, or any 3 of age under 10 or over 40, non-A non-B hepatitis or drug reaction, jaundice more than 7 days before encephalopathy, INR above 3.5 and bilirubin above 300 micromol/L.

  • Is N-acetylcysteine (NAC) only for paracetamol overdose?

    No. NAC is the antidote for paracetamol-induced ALF, but modern evidence supports its use in early non-paracetamol ALF too - it improves transplant-free survival in patients with low-grade encephalopathy from other causes, and most UK liver units now use it in almost all suspected ALF.

  • What is the survival rate after liver transplant for ALF?

    In modern UK series, 1-year survival after super-urgent liver transplant for ALF is around 80%, and 5-year survival 70 to 80%. Outcomes are worse than for elective transplantation because patients are critically unwell at listing, which is why early referral is so important.

  • When should a patient with a paracetamol overdose be discussed with a liver unit?

    Any patient with an INR rising above 3.0 by day 2, worsening acidosis, rising creatinine or any encephalopathy after paracetamol overdose should be discussed with a specialist liver unit urgently. Do not wait for full King's College Criteria - the earlier the conversation, the safer the transfer if needed.

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