Bilirubin metabolism
How haem becomes bilirubin, how the hepatocyte takes it up, conjugates and excretes it, what gut bacteria do to it, and how each step maps to a cause of jaundice, with a steady-state worked example showing why Gilbert syndrome plus haemolysis gives a higher bilirubin than either alone.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Bilirubin comes from haem, mostly old red cells. It travels in blood as unconjugated bilirubin bound to albumin, is conjugated in the liver by UGT1A1, and is pumped into bile by MRP2.
- Each step has a named disorder. Classify any jaundice first by conjugated fraction: under about 20% conjugated points to overproduction or impaired conjugation; over about 50% points to the liver or bile ducts.
- Only conjugated bilirubin reaches urine.
Loading the rest of the note…
Finished reading?
Sources
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease (11th ed.)Elsevier (Feldman, Friedman, Brandt, 2021), 2021
- Sherlock's Diseases of the Liver and Biliary System (13th ed.)Wiley-Blackwell (Dooley, Lok, Garcia-Tsao, Pinzani, 2018), 2018
- Erlinger S, Arias IM, Dhumeaux D. Inherited disorders of bilirubin transport and conjugation: new insights into molecular mechanisms and consequences. Gastroenterology 2014;146(7):1625-38Gastroenterology, 2014
- Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol 2017;112(1):18-35American College of Gastroenterology, 2017
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Turnstile bot check on sign-in and signed-out feedback