What each LFT measures
| Test | Normal Range | What it reflects |
|---|---|---|
| ALT (Alanine aminotransferase) | 7–56 U/L | Liver cell damage — most specific liver enzyme |
| AST (Aspartate aminotransferase) | 10–40 U/L | Liver cell damage — also raised in muscle and heart disease |
| ALP (Alkaline phosphatase) | 44–147 U/L | Liver or bile duct disease; bone disease |
| GGT (Gamma-GT) | Men: <71 U/L; Women: <42 U/L | Bile duct disease; alcohol use |
| Bilirubin (total) | 0.1–1.2 mg/dL | Jaundice — from red cell breakdown or bile duct obstruction |
| Albumin | 3.5–5.0 g/dL | Liver synthetic function — low in chronic liver disease |
| Total protein | 6.3–8.2 g/dL | Combined albumin and globulin |
| INR / Prothrombin time | INR 0.8–1.2 | Clotting factor production — impaired in severe liver disease |
How to read your LFT pattern
Hepatocellular vs cholestatic pattern
Hepatocellular pattern (liver cell damage): ALT and AST raised much more than ALP. Causes: hepatitis (viral, alcoholic, autoimmune), fatty liver disease, paracetamol overdose. Cholestatic pattern (bile duct obstruction): ALP and GGT raised more than ALT and AST. Causes: gallstones, bile duct cancer, primary biliary cholangitis. Mixed pattern: both groups raised — seen in severe hepatitis or drug reactions.
What does a raised ALT mean?
ALT is the most liver-specific enzyme. Causes of raised ALT by level: mild (1–3x normal): fatty liver (NAFLD), alcohol, medications, thyroid disease; moderate (3–10x): hepatitis B or C, drug-induced liver injury, autoimmune hepatitis; severe (>10x): acute viral hepatitis, ischaemic hepatitis ("shock liver"), paracetamol overdose, acute biliary obstruction. Isolated mild ALT elevation (1–2x normal) is very common and often from fatty liver.
LFT checklist for patients
Questions to discuss with your doctor
- Which tests are abnormal — liver enzymes or liver function?
- Is the pattern hepatocellular or cholestatic?
- Do I need a liver ultrasound?
- Should alcohol or medication be reviewed?
- Do I need tests for hepatitis B or C?
- Should I lose weight to help a fatty liver?