Bilirubin
Bilirubin is the yellow waste pigment from haemoglobin breakdown. Elevated levels cause jaundice and signal liver, bile-duct or haemolytic problems.
What it measures
When red blood cells die, their haem breaks down into bilirubin in the spleen. The liver picks up this unconjugated (indirect) bilirubin, attaches sugars to make it water-soluble — conjugated (direct) bilirubin — and excretes it into bile. Total bilirubin is the sum; the direct/indirect ratio tells you WHERE the problem is. Indirect-dominant rise means too much red-cell breakdown or trouble before liver conjugation (Gilbert's syndrome). Direct-dominant rise means trouble AFTER conjugation — bile flow obstruction or liver-cell injury.
What a high value can mean
- Gilbert's syndrome — common benign genetic variant; mild indirect bilirubin rise especially after fasting or illness. No treatment needed.
- Haemolysis — accelerated red-cell breakdown; check reticulocyte count, LDH, haptoglobin.
- Hepatocellular injury — viral hepatitis, drug-induced, NAFLD progression; ALT/AST also elevated.
- Biliary obstruction — gallstones, tumour, primary biliary cholangitis, primary sclerosing cholangitis; alkaline phosphatase + GGT also elevated.
- Neonatal jaundice — physiological in newborns, but extreme levels carry kernicterus risk.
What a low value can mean
- Generally not clinically significant — low bilirubin is benign.
- Some studies link low bilirubin to higher cardiovascular risk but this isn't actionable.
When to discuss with a doctor
Total bilirubin above 2 mg/dL (jaundice threshold) warrants a primary-care visit and additional labs — direct vs indirect breakdown, ALT/AST, alkaline phosphatase, GGT, ultrasound. Sudden jaundice with abdominal pain or fever may be biliary obstruction and needs urgent evaluation. Mediora.AI shows the bilirubin pattern in context with the other liver-panel markers.