Bilirubin in a blood test is a yellow pigment that is produced when the body breaks down old red blood cells. The bilirubin blood test measures the levels of bilirubin in your blood to assess liver function and help diagnose conditions related to the liver, gallbladder, or red blood cells. There are two main types of bilirubin:

• Unconjugated (Indirect) Bilirubin: Produced during the breakdown of hemoglobin from red blood cells.
• Conjugated (Direct) Bilirubin: Processed by the liver and ready to be excreted.

The bilirubin is processed by the liver, mixed with bile, and excreted through the digestive system. If the liver is not functioning properly or the bile ducts are blocked, bilirubin can build up in the blood, causing jaundice (yellowing of the skin and eyes). The test helps diagnose liver diseases (such as hepatitis or cirrhosis), gallbladder disorders, hemolytic anemia (where red blood cells break down too quickly), and is also used to monitor newborn jaundice. Normal ranges for bilirubin in blood typically include:

• Total bilirubin: 0.1 to 1.2 mg/dL
• Direct (conjugated) bilirubin: 0.0 to 0.3 mg/dL
• Indirect (unconjugated) bilirubin is calculated by subtracting direct bilirubin from total bilirubin.

In summary, bilirubin levels in the blood test reflect how well the liver is processing red blood cell breakdown products and can indicate liver or bile duct problems when elevated. This test is important for diagnosing and monitoring several health conditions related to liver function and red blood cell breakdown. If levels are abnormal, further medical evaluation is needed to determine the cause and appropriate treatment. This test is typically done through a simple blood draw and may require fasting beforehand to ensure accurate results. This explanation is based on up-to-date medical sources and hospital guidelines.