A bilirubin test measures the amount of Reference bilirubin Opens New Window in a blood sample. Bilirubin is a brownish yellow substance found in Reference bile Opens New Window. It is produced when the liver breaks down old red blood cells. Bilirubin is then removed from the body through the stool (feces) and gives stool its normal color.
Bilirubin circulates in the bloodstream in two forms:
- Indirect (or unconjugated) bilirubin. This form of bilirubin does not dissolve in water (it is insoluble). Indirect bilirubin travels through the bloodstream to the liver, where it is changed into a soluble form (direct or conjugated).
- Direct (or conjugated) bilirubin. Direct bilirubin dissolves in water (it is soluble) and is made by the liver from indirect bilirubin.
Total bilirubin and direct bilirubin levels are measured directly in the blood, whereas indirect bilirubin levels are derived from the total and direct bilirubin measurements.
When bilirubin levels are high, the skin and whites of the eyes may appear yellow (Reference jaundice Opens New Window). Jaundice may be caused by liver disease (Reference hepatitis Opens New Window), blood disorders (Reference hemolytic anemia Opens New Window), or blockage of the tubes (bile ducts) that allow bile to pass from the Reference liver to the small intestine Opens New Window Reference Opens New Window.
Mild jaundice in newborns usually does not cause problems. But too much bilirubin (hyperbilirubinemia) in a newborn baby can cause brain damage (Reference kernicterus Opens New Window) and other serious problems. So some Reference babies who develop jaundice Opens New Window may need treatment to lower their bilirubin levels.
|By:||Reference Healthwise Staff||Last Revised: Reference May 11, 2012|
|Medical Review:||Reference John Pope, MD - Pediatrics
Reference Chuck Norlin, MD - Pediatrics