Bilirubin (Total and Direct)
Definition
Bilirubin is a yellowish substance formed during the normal breakdown of old red blood cells. It is measured in three forms:
| Form | Description |
|---|---|
| Total bilirubin | Overall measurement |
| Direct (conjugated) | The form processed by the liver |
| Indirect (unconjugated) | The form not yet processed |
Purpose
Investigation of symptoms of jaundice (yellowing of the skin/eyes, dark urine, clay-colored stool, abdominal pain); detection of bile duct obstruction; monitoring of existing liver disease; identification of hemolytic anemia or rapid red blood cell breakdown.
Results
- High, hemolytic anemia, liver disease or bile duct obstruction
- Low, usually not a concern; may be associated with certain medications (antibiotics, birth control pills, epilepsy drugs)
Higher than normal bilirubin levels can also be due to certain medications, certain foods or strenuous exercise.
Normal Values
Laboratory specific. The source notes that ranges vary by sex and by whether the person is an infant/child.
Risks and Limitations
Cannot diagnose liver disease on its own; a liver panel, ultrasound or biopsy may be needed.
Newborn jaundice: Many healthy newborns have jaundice because their liver is not developed enough to clear bilirubin. It is usually harmless, but the test is done to prevent brain damage.