Complete Guide to Liver Function Tests

Liver function tests (LFTs), also called a hepatic panel, are a group of blood tests that measure enzymes, proteins, and substances produced or processed by the liver. They help doctors assess liver health, detect liver damage, and monitor the progression of liver diseases.

A standard liver panel typically includes ALT, AST, ALP, GGT, bilirubin, albumin, and total protein. Abnormal results don't always mean liver disease — medications, intense exercise, and other factors can temporarily affect these values.

ALT is an enzyme found primarily in liver cells. When liver cells are damaged, ALT leaks into the bloodstream, making it one of the most specific markers for liver injury.

High ALT can indicate:

• Non-alcoholic fatty liver disease (NAFLD)
• Hepatitis (viral, alcoholic, or autoimmune)
• Medication-induced liver injury (e.g. acetaminophen, statins)
• Cirrhosis

Mildly elevated ALT (up to 2× the upper limit) is common and may result from obesity, certain medications, or vigorous exercise. Persistently elevated ALT warrants further investigation.

AST is an enzyme found in the liver, heart, muscles, and kidneys. Because it's not liver-specific, AST is usually interpreted alongside ALT for a clearer picture.

High AST can result from:

• Liver disease (hepatitis, cirrhosis)
• Heart attack (myocardial infarction)
• Muscle damage or intense exercise
• Hemolysis (red blood cell breakdown)

The AST/ALT ratio (De Ritis ratio) provides additional diagnostic value. A ratio >2 suggests alcoholic liver disease, while a ratio <1 is more typical of non-alcoholic fatty liver disease or viral hepatitis.

ALP (Alkaline Phosphatase) is an enzyme found in the liver, bile ducts, and bone. Elevated ALP can indicate bile duct obstruction, bone disorders, or liver disease.

GGT (Gamma-Glutamyl Transferase) is an enzyme concentrated in the liver and bile ducts. It is especially sensitive to alcohol use and bile duct problems.

When both ALP and GGT are elevated, the source is most likely hepatobiliary (liver/bile duct). If ALP is elevated but GGT is normal, the elevation is more likely from bone.

Bilirubin is a yellow pigment produced when the body breaks down old red blood cells. The liver processes bilirubin so it can be excreted. Elevated bilirubin causes jaundice (yellowing of skin and eyes).

• High indirect bilirubin: hemolysis, Gilbert syndrome (benign), ineffective erythropoiesis
• High direct bilirubin: bile duct obstruction (gallstones, tumors), hepatitis, cirrhosis
• High total bilirubin: may result from either pre-hepatic, hepatic, or post-hepatic causes

Liver function tests can help identify or monitor several conditions:

• Non-Alcoholic Fatty Liver Disease (NAFLD): Mildly elevated ALT and AST with AST/ALT ratio <1. Often associated with obesity and metabolic syndrome.
• Hepatitis: Significantly elevated ALT and AST (often >10× normal). Can be viral (A, B, C), autoimmune, or drug-induced.
• Cirrhosis: Advanced scarring of the liver. AST/ALT ratio >1, low albumin, elevated bilirubin, and prolonged INR are typical findings.
• Gallstones / Bile duct obstruction: Markedly elevated ALP, GGT, and direct bilirubin with relatively normal ALT and AST.
• Alcoholic Liver Disease: AST/ALT ratio >2, elevated GGT, and elevated MCV are characteristic findings.

Consult your doctor promptly if:

• ALT or AST is more than 3× the upper limit of normal
• Bilirubin is above 2.0 mg/dL with jaundice symptoms
• ALP is significantly elevated with abdominal pain
• You notice yellowing of skin or eyes, dark urine, or pale stools
• Liver enzyme abnormalities persist across multiple tests
• You have risk factors such as heavy alcohol use, obesity, or chronic hepatitis

A single mildly abnormal value is often not concerning, but patterns and trends over time carry diagnostic significance.

NoryaAI reads your liver function test results — whether from a PDF, lab printout, or photo — and automatically:

• Identifies ALT, AST, ALP, GGT, bilirubin, albumin, and total protein
• Compares each value to reference ranges adjusted for age and sex
• Calculates the AST/ALT ratio and interprets its significance
• Flags abnormal values with clear, easy-to-understand explanations
• Generates a structured, doctor-ready health summary

Upload your blood test report and get your liver panel analysis in minutes — no manual data entry required.