Given just how much lifestyle disorders or non-communicable diseases are on the rise these days, it is quite likely that you would have taken a liver function test (LFT) and then consulted the doctor about that one line that could make anybody nervous: LFT abnormal. Liver function tests (LFTs) are common, inexpensive blood tests that clinicians use to screen for liver disease, monitor known liver conditions, or check for drug effects. And while this means that most people get LFTs done as a part of routine blood tests, most aren't able to understand what the reports indicate because LFTs are not a single number like in a lipid profile.
They're a panel of markers that tell different parts of the liver story. Some tests (ALT, AST) signal injury to liver cells. Others (ALP, GGT, bilirubin) suggest problems with bile flow, while albumin and INR reflect the liver's synthetic power. Interpreting LFTs is about patterns, not panic. The combination, degree of elevation, clinical context and trends over time guide next steps.
In this Health Decoder we unpack common LFT markers, how to read the typical patterns (hepatocellular vs cholestatic), common causes, and why isolated abnormal values don't always equal severe liver disease. If you've seen an "abnormal LFT" on your report, this primer will help you understand what your doctor is looking for and what to ask next.
What's In An LFT Panel? The Key Markers, Explained
The following are the key markers in an LFT panel and what they stand for:
- ALT (alanine aminotransferase): A liver enzyme, this rises when liver cells are injured (normal ranges vary).
- AST (aspartate aminotransferase): Found in liver and other tissues (muscle, heart), this marker is elevated with hepatic injury but less liver-specific than ALT.
- ALP (alkaline phosphatase): This marker is concentrated in bile ducts and bone. High levels suggest cholestasis or biliary obstruction when disproportionate to ALT/AST.
- GGT (gamma-glutamyl transferase): This marker helps confirm that an ALP rise is from the liver rather than bone; sensitive to alcohol and biliary disease.
- Total and direct bilirubin: This marker is the product of red-cell breakdown. An elevated conjugated (direct) bilirubin suggests cholestasis, while unconjugated rises point to haemolysis or Gilbert's.
- Albumin and total protein: This reflects synthetic function, where low albumin suggests chronic liver dysfunction or malnutrition.
- Prothrombin time or INR: This is the most sensitive routine marker of liver synthetic failure; a prolonged INR is a red flag for severe dysfunction.
Note: Reference ranges differ slightly between labs. Your lab report will show its own normal intervals.
Patterns Matter: Hepatocellular Vs Cholestatic Vs Mixed Markers
Clinicians look for patterns rather than single numbers. The R-value (ratio of ALT/ALP relative to their upper limits) helps classify injury:
- Hepatocellular pattern: ALT/AST >> ALP. Seen in viral hepatitis, autoimmune hepatitis, non-alcoholic fatty liver disease (NAFLD), ischemic injury and many drug-related injuries. Very high ALT/AST (>1,000 IU/L) suggests severe acute injury such as paracetamol overdose or acute viral hepatitis.
- Cholestatic pattern: ALP and bilirubin predominate (with or without GGT rise). Suggests bile duct obstruction (gallstones, strictures), primary biliary cholangitis, or drug-induced cholestasis.
- Mixed pattern: Both enzyme groups elevated, which is common in many liver diseases and certain drug toxicities. Guidelines recommend further imaging and evaluation based on the pattern and clinical picture.
Common Causes Behind Abnormal LFTs
Non-alcoholic fatty liver disease (NAFLD): The most common cause of mild ALT/AST elevation in many populations, linked to obesity, insulin resistance and metabolic syndrome.
- Alcoholic liver disease: Heavy drinking raises GGT and AST (often AST>ALT).
- Viral hepatitis (A, B, C): These can cause abrupt, marked ALT/AST elevation and jaundice. Screening tests are essential if viral cause is suspected.
- Drug-induced liver injury (DILI): Many prescription and over-the-counter drugs (including supplements and herbal products) can cause LFT abnormalities; degree and pattern vary.
- Cholestatic disease: Gallstones, biliary obstruction, primary biliary cholangitis or sclerosing cholangitis raise ALP and bilirubin. Imaging (ultrasound, MRCP) is the next step.
- Autoimmune and genetic disorders: Autoimmune hepatitis, haemochromatosis and Wilson disease show particular lab and clinical clues and warrant specialist workup.
When To Worry
Seek urgent medical attention if you have jaundice (yellow eyes/skin), severe abdominal pain, persistent vomiting, confusion or an INR that is prolonged. These can indicate acute liver failure or serious biliary obstruction. Extremely high transaminases also prompt emergency evaluation.
Can LFT Reports Be "Normal" But Disease Present?
Yes. LFTs are helpful but imperfect. Early chronic liver disease (especially some cases of NAFLD) can present with near-normal enzymes, and advanced fibrosis can sometimes occur with only modest enzyme elevation. That's why doctors combine LFTs with risk-factor assessment, imaging and fibrosis markers when screening at-risk patients.
Liver function tests are a powerful first step in detecting liver problems, but the story lies in the pattern, magnitude and clinical context. Mild abnormalities are common and often reversible. Marked elevations or signs of liver dysfunction require urgent evaluation. If you encounter an abnormal LFT, ask your clinician: which pattern is this (hepatocellular vs cholestatic), what are the likely causes given my history, what further tests are needed, and what lifestyle or treatment steps should I start now? Clear answers, trend monitoring and targeted investigation are the heart of good liver care.
Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your doctor for more information. NDTV does not claim responsibility for this information.
