Bilirubin is a yellow pigment formed when red blood cells break down. The liver processes bilirubin and excretes it through bile into the intestines. When this process slows or becomes blocked, bilirubin can build up in the blood, sometimes leading to visible jaundice (yellowing of the skin and eyes).
Did you know? Mild bilirubin elevation after fasting or illness is common, especially in people with a harmless condition called Gilbert syndrome.
Two forms of bilirubin
- Indirect (unconjugated): rises when red cells break down faster or the liver temporarily struggles to process bilirubin.
- Direct (conjugated): rises when bile cannot flow freely — for example, due to gallstones, liver inflammation, or bile duct blockage.
Common causes of high bilirubin
- Viral hepatitis or liver inflammation
- Gallstones or bile duct obstruction
- Gilbert syndrome (benign)
- Hemolytic anemia (red cell breakdown)
- Alcoholic or fatty liver disease
- Drug- or toxin-related liver injury
When to discuss with your clinician
- Persistent or marked elevation (>2 mg/dL)
- Associated symptoms (jaundice, fatigue, dark urine)
- Elevated ALP or GGT suggesting bile flow issues
- History of hepatitis, alcohol use, or gallstones
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