Bilirubin

Background

• Breakdown product of hemoglobin; conjugated (direct) by the liver and excreted in bile

Normal Values

• Total bilirubin: 0.1-1.2 mg/dL
• Direct (conjugated): 0-0.3 mg/dL
• Indirect (unconjugated): 0.2-0.8 mg/dL

Interpretation

• Jaundice visible when total bilirubin >2.5-3.0 mg/dL
• Elevated direct (conjugated) bilirubin: biliary obstruction (choledocholithiasis, malignancy), hepatocellular disease, sepsis
• Elevated indirect (unconjugated) bilirubin: hemolysis, Gilbert syndrome (benign, affects ~5% of population), ineffective erythropoiesis
• Direct bilirubin >50% of total suggests obstructive or hepatocellular process
• In neonates, unconjugated hyperbilirubinemia requires evaluation for kernicterus risk

See Also

• Liver function tests
• Choledocholithiasis
• Jaundice
• Neonatal jaundice