Bilirubin

What is Bilirubin?

Bilirubin is a yellow-orange pigment produced when red blood cells break down at the end of their ~120-day lifespan. Your spleen breaks down old red blood cells, releasing hemoglobin, which is then converted to bilirubin.

Bilirubin travels to your liver, which processes it and excretes it in bile. This is why urine is yellow and stool is brown — both contain bilirubin byproducts.

When this system malfunctions, bilirubin builds up in the blood, causing jaundice (yellowing of skin and eyes).

Normal Ranges

Type	Normal Range
Total bilirubin	0.1–1.2 mg/dL
Direct bilirubin	0.0–0.3 mg/dL
Indirect bilirubin	0.2–0.9 mg/dL

Why It Matters

Jaundice Detection

Bilirubin above ~2.5 mg/dL causes visible yellowing of skin and eyes (jaundice). This requires investigation.

Liver Function Assessment

The liver processes bilirubin. Elevated direct bilirubin suggests liver disease or bile duct obstruction.

Red Blood Cell Disorders

Excessive red blood cell breakdown produces too much bilirubin, raising indirect bilirubin.

High Bilirubin Causes

Hemolytic anemia — Excessive red blood cell breakdown
Hepatitis — Viral, alcoholic, autoimmune
Cirrhosis — Liver scarring
Bile duct obstruction — Gallstones, tumors
Gilbert's syndrome — Common, benign genetic condition

How Often to Test

Routine checkups: Often included in metabolic panels
Liver disease: Every 3–6 months
Jaundice present: Immediately