Bilirubin (Total)
Hemoglobin breakdown product – marker for liver health, bile flow, and hemolysis
Also known as
Definition
Bilirubin is the end product of hemoglobin degradation. Indirect (unconjugated) bilirubin arises from heme breakdown in the reticuloendothelial system, is converted to direct (conjugated) bilirubin in the liver, and excreted in bile. Elevated total bilirubin values indicate impaired hemoglobin breakdown (hemolysis), liver disease, or bile duct obstruction — clinically manifesting as jaundice (icterus).
| Parameter | Value |
|---|---|
| Unit | µmol/l (mg/dl) |
| Reference Range | Total: < 21 µmol/l (< 1.2 mg/dl) | Direct (conjugated): < 5 µmol/l (< 0.3 mg/dl) | Indirect: < 17 µmol/l (< 1.0 mg/dl) |
Agree on your personal target range with your doctor.
Conversion: 1 mg/dl = 17.1 µmol/l. US labs: total bilirubin < 1.2 mg/dl; direct < 0.3 mg/dl.
↓ What a low value means
Very low bilirubin (< 3 µmol/l) has no clinical significance. Some studies show that lower bilirubin levels (in the lower reference range) are associated with increased oxidative stress and slightly higher cardiovascular risk — bilirubin acts as an endogenous antioxidant.
↑ What a high value means
Elevated total bilirubin: predominantly indirect bilirubin suggests hemolysis (antibodies, G6PD deficiency), ineffective erythropoiesis, or Gilbert's syndrome (benign). Predominantly direct bilirubin suggests liver disease (hepatitis, cirrhosis) or bile duct obstruction (gallstones, tumor). Visible jaundice (first in the sclera) appears above 34 µmol/l.
✓ What can influence this value
Bilirubin is formed when heme is broken down (heme oxygenase pathway) and is excreted via the liver and bile. The value is influenced by increased breakdown of red blood cells (hemolysis), liver diseases, bile duct obstruction, and alcohol consumption. Fasting and infections can raise the value temporarily; in Gilbert's syndrome the value often fluctuates without disease significance. The assessment is made by the treating doctor.
When to test
Routinely in liver panels. Also measured with jaundice, dark urine, upper abdominal pain, suspected hepatitis, in a hemolysis workup and in newborn screening (neonatal jaundice). Fractionation (direct/indirect) helps distinguish possible causes.
Frequently asked questions
What is Gilbert's syndrome and is it dangerous? +
Gilbert's syndrome is a benign genetic variant (UGT1A1 polymorphism) in which bilirubin is not fully conjugated, leading to mildly elevated indirect bilirubin (17–51 µmol/l). It is clinically harmless, though occasional jaundice can appear with stress, fasting, or illness. Interestingly, carriers of Gilbert's syndrome show lower rates of heart disease and gallbladder cancer in studies.
Can I measure bilirubin to assess my liver status? +
Bilirubin alone is non-specific, but important in the context of a full liver panel (GOT, GPT, GGT, ALP, albumin, PT). Elevated bilirubin with other abnormal liver values indicates more severe liver dysfunction. Bilirubin typically rises later than GOT/GPT/GGT with liver injury.
Why are newborns screened for elevated bilirubin? +
In the first days of life, newborns have physiologically elevated bilirubin (breakdown of fetal hemoglobin, immature liver). Above certain thresholds, bilirubin can cross the blood-brain barrier and damage the basal ganglia of the immature brain (kernicterus). Early medical assessment and treatment can prevent permanent neurological damage. According to NICE guideline CG98, jaundice in the first 24 hours of life needs urgent medical assessment. Thresholds and the choice of treatment, such as phototherapy, lie with the care team.
Bilirubin (Total)
Sources
Last updated: May 28, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.