Blood Tests for Liver Disease: The Full Panel Explained
The liver panel (LFTs) identifies liver damage, assesses severity, and distinguishes between different types of liver disease. Understanding the pattern of elevated enzymes is more clinically useful than any single elevated value.
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| Test | Normal Range | What It Measures |
|---|---|---|
| ALT (alanine aminotransferase) | 7–56 U/L | Liver-specific enzyme released during hepatocyte damage — the best marker of liver injury |
| AST (aspartate aminotransferase) | 10–40 U/L | Less liver-specific — also elevated in muscle damage, heart attack, and strenuous exercise |
| ALP (alkaline phosphatase) | 44–147 U/L | Elevated in bile duct obstruction, bone disease, and some liver conditions |
| GGT (gamma-glutamyl transferase) | 9–48 U/L | Sensitive to bile duct disease and alcohol use — often the first to rise in alcohol-related damage |
| Total bilirubin | 0.2–1.2 mg/dL | Reflects red blood cell breakdown and liver excretion of waste products |
| Albumin | 3.5–5.0 g/dL | Liver synthesis marker — low albumin indicates reduced synthetic capacity (serious) |
| PT/INR | INR below 1.2 | Clotting factors made by the liver — prolonged INR indicates synthetic failure |
Liver Panel — Key Markers and What They Measure
Reading the Pattern
Hepatocellular pattern (mainly ALT and AST elevated, AST:ALT ratio matters): Marked elevation (above 10-20x normal) suggests acute hepatitis — viral (hepatitis A, B, C), drug-induced, alcoholic, or ischaemic. Mild-moderate elevation (1-3x normal) is most commonly non-alcoholic fatty liver disease (NAFLD), mild alcoholic liver disease, or medication effects. An AST:ALT ratio above 2:1 strongly suggests alcoholic liver disease.
Cholestatic pattern (mainly ALP and GGT elevated): Suggests bile duct obstruction (gallstones, strictures, cancer), primary biliary cholangitis, or primary sclerosing cholangitis. GGT elevation without ALP elevation is typically caused by alcohol or certain medications (it is induced by many drugs).
Mixed pattern: Both hepatocellular and cholestatic markers elevated — seen in many conditions including drug-induced liver injury and some viral hepatitis presentations.
When Liver Tests Are Mildly Elevated
The most common cause of mildly elevated ALT (1.5–3x normal) in the US is non-alcoholic fatty liver disease (NAFLD), now called metabolic dysfunction-associated steatotic liver disease (MASLD). It affects approximately 38% of the US population and is closely associated with obesity, type 2 diabetes, and metabolic syndrome. Many people have no symptoms — elevated liver enzymes on a routine panel are often how it is first detected.
Pattern Recognition Is More Useful Than Individual Values
ALT+AST elevated with normal ALP/GGT = hepatocellular disease (hepatitis, fatty liver). ALP+GGT elevated with normal transaminases = cholestatic disease (bile duct obstruction, gallstones, primary biliary cholangitis). Both elevated = mixed picture. Albumin and bilirubin reflect severity, not cause.
Markers of Liver Synthetic Function
Albumin and INR (or prothrombin time) measure the liver's ability to make proteins. Unlike ALT and AST — which measure damage — albumin and INR measure function. Low albumin and elevated INR in the context of liver disease indicate the liver's reserve is compromised. These are key components of the Child-Pugh score used to stage cirrhosis severity.
Medical Disclaimer
This article is for educational purposes only and does not constitute medical advice. Reference ranges, supplement dosages, and nutritional information mentioned are general educational guidance from published research—not personalised recommendations. Do not use this content to self-diagnose or self-treat any condition. Always consult a qualified healthcare provider before making any changes to your health regimen, medications, or supplements.
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