Bilirubin (Total & Direct)
Also known as: Total bilirubin, Direct bilirubin, Indirect bilirubin, Conjugated/unconjugated bilirubin
Bilirubin is the yellow pigment produced when red blood cells are broken down. High bilirubin causes jaundice and signals problems with red cell destruction, liver processing, or bile duct drainage.
Venous blood (serum separator tube — protect from light)
2–4 hours
Not required
Liver Function
Reference Ranges
| Measurement | Reference Range | Unit |
|---|---|---|
| Total bilirubin | 0.1 – 1.2 | mg/dL |
| Direct (conjugated) bilirubin | ≤ 0.3 | mg/dL |
| Indirect (unconjugated) bilirubin | ≤ 0.9 | mg/dL |
Reference ranges are typical adult values. Your laboratory may use slightly different intervals — always use your lab's reported reference.
What This Test Measures
When RBCs are destroyed, haem is converted to unconjugated (indirect) bilirubin — fat-soluble, toxic to the brain. The liver conjugates it (makes it water-soluble), and it is excreted in bile. Total bilirubin = direct (conjugated) + indirect (unconjugated). The ratio between them localises the problem: excess unconjugated suggests haemolysis or Gilbert's syndrome; excess direct bilirubin suggests liver cell damage or bile duct obstruction.
When Is This Test Ordered?
- Jaundice evaluation
- Liver function testing
- Haemolytic anaemia investigation
- Neonatal jaundice monitoring
- Bile duct obstruction assessment
When Results Are High
Above 2 mg/dL causes clinically visible jaundice (scleral icterus first). Predominantly unconjugated: haemolysis (high RBC breakdown) or Gilbert's syndrome (benign impaired conjugation). Predominantly conjugated: hepatocellular disease (hepatitis, cirrhosis) or biliary obstruction (gallstones, pancreatic cancer, cholestasis).
When Results Are Low
Low bilirubin has no clinical significance.
Factors That Can Affect Your Result
- Fasting raises bilirubin by 50–100% through inhibition of conjugation — avoid prolonged fasting before testing
- Haemolysis in the sample tube may raise bilirubin
- Protect sample from light — bilirubin is photo-degraded
- Gilbert's syndrome — benign genetic condition causing unconjugated bilirubin up to 3–4 mg/dL, consistently; more pronounced after fasting or illness
Tracking This Test Over Time
In Gilbert's syndrome, bilirubin classically peaks during fasting or intercurrent illness and returns to normal when well. If jaundice appears only during these triggers and all liver enzymes are normal, Gilbert's syndrome is the likely explanation — a benign finding requiring no treatment.
Track your Bilirubin in LoomsRelated Tests
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Medical disclaimer
This page is for educational purposes only and does not constitute medical advice. Reference ranges vary between laboratories, and results must be interpreted in the context of your symptoms, history, and other tests. Always discuss your results with your healthcare provider. Content reviewed by the Looms medical team, 2026-06-01.