Total Bilirubin
A yellow pigment made when red blood cells break down, processed and excreted by the liver.
| Typical reference range | 0.2–1.2 mg/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
When old red blood cells are recycled, hemoglobin is converted to bilirubin. Unconjugated (indirect) bilirubin travels to the liver, where it is conjugated (made water-soluble, direct) and excreted in bile. Total bilirubin is the sum of both forms.
Why it matters
Bilirubin reflects the balance between red cell breakdown and liver processing and bile flow. High levels cause jaundice. Mildly elevated bilirubin from Gilbert's syndrome is benign and has even been associated with lower cardiovascular risk due to bilirubin's antioxidant effects.
What a high result can mean
The most common cause of mild isolated elevation is Gilbert's syndrome (reduced conjugation, affecting ~5-10% of people), often worsened by fasting, illness or exertion. Other causes include hemolysis, hepatitis, cirrhosis, bile duct obstruction and certain medications.
What a low result can mean
Low bilirubin is generally not a concern; some studies link lower values with higher oxidative stress and cardiovascular risk.
What affects the result
Fasting, dehydration and recent illness can raise levels, especially in Gilbert's syndrome. Look at the direct/indirect split, liver enzymes and a CBC (to check for hemolysis) to interpret elevations.
Units and conversion
Usually reported in mg/dL.
- From umol/L: multiply by 0.058 to get mg/dL
- From mmol/L: multiply by 58.48 to get mg/dL
Also called on lab reports
Bilirubin, Total, Bilirubin, T. Bili, Bilirubin Total, Bilirubin, Total, Serum, TBIL
Related tests: Liver
This page is educational and does not replace advice from a healthcare professional.