Blood will be collected after venepuncture from all patients for complete blood counts, Serum bilirubin (direct and indirect), aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma glutamyl transferase, prothrombin time and INR, urea, creatinine, sodium, potassium, serum total protein and albumin, within 24 hours after admission and twice a week there after or as and when needed.

Time line for blood tests and evaluation of clinical parameters & 13C-MBT

For ALF patients:

On days 0, 1, 3, and 7

For ACLF patients:

On days 0, 7 (week 1), 14(week 2), 28 (weeks 4)

Blood tests would include:

Serum bilirubin (total and direct), aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma-glutamyltransferase, Serum proteins (total and albumin), prothrombin time & international normalized ratio (INR), Serum urea and creatinine, serum electrolytes, arterial ammonia and arterial blood gas analysis.

Inclusion Criteria:

- All patients presenting with acute liver failure and acute on chronic liver failure (between 18 - 70 years of age) to Institute of Liver & Biliary Sciences (ILBS), New Delhi, India.

Exclusion Criteria:

1. Patients with significant co-morbid illnesses such as cardiovascular or respiratory or intrinsic renal diseases which by themselves may have a bearing on the outcome.
2. Patients with previous intestinal bypass surgery for morbid obesity
3. Patients with extensive small bowel resection
4. Patients currently receiving total parenteral nutrition
5. Pregnant women
6. Patients with history of allergy to paracetamol
7. Patients on steroids or anti-fungal agents
8. Patients in encephalopathy
9. Patients unwilling to participate in the protocol
10. Patients on medications which can alter the activity of CYP 1A2 enzymes such as corticosteroids, amiodarone, tetracycline, niacin, valproic acid, methotrexate, stavudine and zidovudine.