Heme breakdown product — elevations signal liver dysfunction, hemolysis, or the benign Gilbert syndrome variant.
Bilirubin is produced when heme is broken down. Liver conjugation and biliary excretion keep levels low. Elevations above ~3 mg/dL produce visible jaundice. Isolated mild elevation (1.2–2.5, normal ALT/AST) is often Gilbert syndrome — a benign genetic variant in UGT1A1 affecting ~5% of people, with no clinical implications.
Direct (conjugated) vs indirect (unconjugated) fractionation distinguishes hemolysis from hepatobiliary obstruction.
Bilirubin is influenced by: liver conjugation capacity (Gilbert syndrome lowers it), biliary obstruction (raises direct), hemolysis (raises indirect), fasting (raises it in Gilbert), and drugs (some antibiotics, protease inhibitors).
Part of a comprehensive metabolic panel. Isolated elevation with normal ALT/AST and no symptoms is almost always Gilbert — benign. Persistent rise alongside ALT/AST warrants hepatic workup.
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Start tracking →Informational only — not medical advice. Reference ranges vary by lab and individual context. Work with a licensed provider to interpret your specific results.