Bilirubin is a yellow pigment formed as hemoglobin from worn-out red blood cells breaks down. The liver takes it up, neutralizes it and excretes it with the bile.
Bilirubin reflects both liver function and the breakdown of red cells. When there is too much of it, the skin and the whites of the eyes turn yellow — this is jaundice.
Reference ranges
Approximate reference for adults:
| Total bilirubin | 3.4 – 20.5 µmol/L |
| Direct (conjugated) | up to 5.1 µmol/L |
| Indirect (unconjugated) | up to 15.4 µmol/L |
What an elevated level means
The causes of a rise depend on the fraction:
Driven by indirect: Gilbert syndrome (a common benign trait, in up to 5–10% of people), increased red-cell breakdown (hemolysis), fasting.
Driven by direct: liver diseases (hepatitis, cirrhosis), impaired bile flow (stones, tumors).
If only indirect bilirubin is elevated with normal liver enzymes, it is most often harmless Gilbert syndrome.
What a low level means
A low bilirubin has no clinical significance and needs no correction.
How the test is done
Venous blood, fasting, in the morning.
Important: fasting and dehydration raise indirect bilirubin, so do not extend the food-free interval beyond 12 hours and do drink water. Ask for the fractions (direct and indirect) to be measured, not just the total.
What affects the value
- Gilbert syndrome — a common hereditary cause of a mild rise in indirect bilirubin.
- Fasting — raises indirect bilirubin.
- Red-cell breakdown (hemolysis) — raises the indirect fraction.
- Liver and biliary diseases — raise the direct fraction.
- Some medications — affect the level.
Calculate using this marker
Calculators where Bilirubin is used directly:
Frequently asked questions
Bilirubin is high but the liver is fine — what is that?
Most often it is Gilbert syndrome: a hereditary trait with mildly elevated indirect bilirubin and normal liver enzymes (ALT, AST). It is not a disease and needs no treatment, though bilirubin can rise with fasting, stress and infections.
At what bilirubin level does jaundice appear?
Yellowing of the skin and sclerae usually becomes noticeable when total bilirubin is above about 40 µmol/L. At lower values the rise is visible only in the test.
Is a high bilirubin dangerous?
It depends on the cause. Gilbert syndrome is safe. But a rise driven by direct bilirubin (liver disease, bile stasis) or marked hemolysis calls for evaluation by a doctor.