Decoding Your Liver Function Test

Why Your Liver Matters

Your liver is a metabolic powerhouse performing over 500 functions: detoxification, protein synthesis, bile production, glucose regulation, nutrient storage, and more. It's remarkably resilient—but when it's damaged, the consequences can be severe.

The challenge: Liver disease often progresses silently. You can lose 70-80% of liver function before symptoms appear. That's why routine liver function tests are critical for early detection.

Key Biomarkers Explained

ALT (Alanine Aminotransferase)

What it is: An enzyme primarily found in liver cells. Released into blood when liver cells are damaged.

Reference range: 7-56 U/L (varies by lab)

Optimal range: < 30 U/L for men, < 25 U/L for women

What elevations mean: ALT is the most specific marker for liver damage. High levels suggest hepatocellular injury from viral hepatitis, fatty liver disease, alcohol, medications, or autoimmune conditions.

AST (Aspartate Aminotransferase)

What it is: An enzyme found in liver, heart, muscle, and other tissues.

Reference range: 10-40 U/L

Optimal range: < 30 U/L

What elevations mean: Less liver-specific than ALT. Can be elevated due to heart attack, muscle injury, or liver disease. The AST/ALT ratio helps distinguish causes (ratio >2 suggests alcohol-related liver damage).

GGT (Gamma-Glutamyl Transferase)

What it is: An enzyme involved in glutathione metabolism, found mainly in liver and bile ducts.

Reference range: 9-48 U/L

Optimal range: < 30 U/L

What elevations mean: Sensitive to alcohol consumption and bile duct obstruction. Also elevated in fatty liver disease, diabetes, and oxidative stress. A "canary in the coal mine" for metabolic dysfunction.

Alkaline Phosphatase (ALP)

What it is: An enzyme found in liver, bone, and intestines.

Reference range: 44-147 U/L

What elevations mean: High ALP + high GGT suggests bile duct obstruction or cholestatic liver disease. High ALP alone may indicate bone disease.

Bilirubin (Total & Direct)

What it is: A yellow pigment from red blood cell breakdown, processed by the liver.

Reference range: Total 0.1-1.2 mg/dL, Direct < 0.3 mg/dL

What elevations mean: High bilirubin causes jaundice (yellowing of skin/eyes). Elevated direct bilirubin suggests liver or bile duct problems. Elevated indirect bilirubin may indicate hemolysis or Gilbert's syndrome (benign genetic condition).

Common Causes of Elevated Liver Enzymes

🍔 Non-Alcoholic Fatty Liver Disease (NAFLD)

Most common cause. Affects 25-30% of adults. Linked to obesity, diabetes, and metabolic syndrome.

🍺 Alcohol

Chronic alcohol consumption damages liver cells. AST/ALT ratio > 2 is a clue.

💊 Medications

Acetaminophen, statins, antibiotics, and many others can elevate liver enzymes.

🦠 Viral Hepatitis

Hepatitis B and C cause chronic liver inflammation and damage.

🧬 Autoimmune Hepatitis

Immune system attacks liver cells. More common in women.

🏋️ Vigorous Exercise

Can temporarily elevate AST and ALT. Retest after a few days of rest.

How to Improve Your Liver Health

⚖️ Weight Loss (Most Impactful for NAFLD)

Losing 7-10% of body weight can significantly reduce liver fat and inflammation. Even 3-5% helps.

🚫 Limit Alcohol

For those with elevated enzymes, consider abstaining completely or limiting to <2 drinks/week.

🥗 Anti-Inflammatory Diet

✓Reduce refined sugars and fructose (major drivers of fatty liver)
✓Increase vegetables, lean protein, healthy fats
✓Coffee (2-3 cups/day) is protective against liver disease

🏃 Exercise

Reduces liver fat independent of weight loss. Aim for 150+ minutes of moderate activity per week.

When to See a Doctor

⚠️ALT or AST > 2x upper limit of normal (persistent)
⚠️Elevated bilirubin (jaundice, dark urine, pale stools)
⚠️Unexplained fatigue, abdominal pain, or swelling
⚠️Progressive enzyme elevations despite lifestyle changes

Further testing may include: Ultrasound, FibroScan, hepatitis panel, autoimmune markers, or liver biopsy.