Bilirubin (Total, Direct, Indirect) – Serum Test
Overview
Bilirubin is a yellow pigment formed during the breakdown of hemoglobin in red blood cells. It is processed by the liver and excreted through bile. Measuring bilirubin levels helps evaluate liver function, red blood cell turnover, and bile duct integrity. The test includes three components:

Total Bilirubin: The sum of both direct and indirect bilirubin.

Direct Bilirubin (Conjugated): Water-soluble, processed by the liver.

Indirect Bilirubin (Unconjugated): Fat-soluble, not yet processed by the liver.

Purpose of the Test
This test is used to:

Evaluate jaundice (yellowing of skin/eyes)

Diagnose and monitor liver diseases (hepatitis, cirrhosis)

Detect bile duct obstructions

Investigate hemolytic anemia

Monitor neonatal jaundice in newborns

Sample Type
Serum: A blood sample is drawn, allowed to clot, and the serum is separated for analysis.

Preparation: Fasting may be recommended for accurate results.

Normal Reference Ranges (may vary slightly by lab):
Total Bilirubin: 0.3 – 1.2 mg/dL

Direct Bilirubin: 0.1 – 0.3 mg/dL

Indirect Bilirubin: Calculated as Total – Direct

What Elevated Levels May Indicate
High Indirect Bilirubin:

Hemolytic anemia

Gilbert’s syndrome

Crigler-Najjar syndrome

Newborn jaundice

High Direct Bilirubin:

Hepatitis

Bile duct obstruction (e.g., gallstones, tumors)

Liver damage or cirrhosis

Symptoms Prompting the Test
Yellow skin or eyes (jaundice)

Dark urine

Pale stools

Fatigue or weakness

Abdominal pain (especially near the liver)

Clinical Use
Differentiates cause of jaundice (pre-hepatic, hepatic, or post-hepatic)

Monitors liver health over time in chronic liver conditions

Assists in diagnosing metabolic or genetic conditions involving bilirubin metabolism

Conclusion
The Bilirubin (Total, Direct, Indirect) test provides essential insight into liver function, red blood cell breakdown, and bile duct health. It plays a key role in diagnosing liver disease, hemolysis, and jaundice-related conditions. Serum is the preferred sample type for accurate analysis.