Bilirubin
The optimal range for Bilirubin (Total Bilirubin) is commonly cited as 0.3–1.0 mg/dL, tighter than the standard lab reference range of 0.1–1.2 mg/dL. Heme breakdown product - elevations signal liver dysfunction, hemolysis, or the benign Gilbert syndrome variant.
How Bilirubin ranges relate
The standard lab range vs the optimization-focused target. Illustrative trajectory shows what a 12-week improvement pattern looks like — not real user data.
What Bilirubin Measures
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.
What Affects This Biomarker
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).
In the Context of Peptide Protocols
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.
Frequently Asked Questions
What does Bilirubin measure?
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.
What is the optimal range for Bilirubin?
The optimal range for Bilirubin is commonly cited as 0.3–1.0 mg/dL. The standard lab reference range is 0.1–1.2 mg/dL.
What affects Bilirubin levels?
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).
Where This Fits in Your Panel
Bilirubin is one marker on a fuller panel. The Peptide Blood Work Checklist lays out the complete baseline panel, what to add by protocol type, and when to retest.
See the full blood work checklist →Upload any lab PDF and MyProtocolStack maps your values to Bilirubin and 40+ other biomarkers. StackAI interprets the trend in context of your protocol.
Start tracking →Last reviewed: June 2026
Informational only - not medical advice. Reference ranges vary by lab and individual context. Work with a licensed provider to interpret your specific results.