Total Bilirubin
Total Bili· also: TB, T.Bili, Total Bilirubin
Clinical Overview
Bilirubin is the breakdown product of heme from red blood cells. Total bilirubin consists of unconjugated (indirect) bilirubin and conjugated (direct) bilirubin. Elevated bilirubin causes jaundice (yellowing of skin and eyes). The type of bilirubin elevated helps identify the cause.
Why This Test Matters
The pattern of bilirubin elevation (direct vs. indirect) localizes the cause. Predominantly indirect hyperbilirubinemia suggests hemolysis or Gilbert's syndrome. Predominantly direct hyperbilirubinemia suggests liver disease or biliary obstruction. Total bilirubin is included in the MELD score (liver transplant priority) and Child-Pugh score (cirrhosis severity). Neonatal jaundice with high unconjugated bilirubin can cause brain damage (kernicterus) and must be treated urgently.
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 0.2 – 1.2 | mg/dL | — |
Also reported in: µmol/L.Conversion factor: 1 µmol/L = 17.094 mg/dL.
Critical (Panic) Values
Critical High: > 20 mg/dL. Values outside these limits require immediate clinical attention.
What Causes Abnormal Results?
High Total Bili Causes
- Hepatocellular disease: viral hepatitis, alcoholic hepatitis, cirrhosis
- Cholestasis: bile duct stones, cholangitis, drug-induced cholestasis
- Hemolysis: sickle cell disease, G6PD deficiency, immune hemolytic anemia
- Gilbert's syndrome (benign unconjugated hyperbilirubinemia)
- Neonatal jaundice
- Crigler-Najjar syndrome (rare)
Low Total Bili Causes
- Not clinically significant (low bilirubin is normal)
Signs & Symptoms to Watch For
How to Prepare for This Test
Fasting for 4 hours preferred. Avoid prolonged sunlight exposure of the sample (light degrades bilirubin). Avoid testing during fasting for Gilbert's (fasting raises bilirubin in this condition).
Factors That Can Affect Results
- Light exposure (degrades bilirubin — sample must be protected)
- Lipemia (interferes with spectrophotometric measurement)
- Hemolysis of sample (releases hemoglobin, interfering with bilirubin measurement)
- Fasting (raises unconjugated bilirubin in Gilbert's syndrome)
Related Topics
Frequently Asked Questions
What is Gilbert's syndrome?
Gilbert's syndrome is a benign, genetic condition where mildly elevated unconjugated (indirect) bilirubin occurs due to reduced UDP-glucuronosyltransferase activity. It affects 3–10% of the population. Bilirubin typically ranges from 1.2–3 mg/dL and rises with fasting, stress, illness, or alcohol. It causes no liver damage and requires no treatment — only reassurance.
At what bilirubin level does jaundice become visible?
Jaundice (visible yellowing of the skin and whites of the eyes) typically becomes clinically apparent when total bilirubin exceeds 2–3 mg/dL (34–51 µmol/L). The sclera (whites of the eyes) is the most sensitive location for detecting early jaundice because of their high elastin content, which binds bilirubin avidly.
What is the difference between direct and indirect bilirubin?
Indirect (unconjugated) bilirubin is the fat-soluble form released from hemoglobin breakdown. Direct (conjugated) bilirubin has been processed by the liver and is water-soluble. Elevated indirect bilirubin points to hemolysis or Gilbert's syndrome. Elevated direct bilirubin points to liver disease or bile duct obstruction. Total bilirubin = direct + indirect.