Bilirubin Test | About, Purpose, Uses, Interpretation & More

Bilirubin is a ubiquitous substance in the blood and the stools. It circulates in the blood in two forms: conjugated and unconjugated, the latter being the predominant form. It is a fundamental test to measure liver function and detect impairments in the metabolism and transport of bilirubin. In most cases, a high level of bilirubin points to a blockage in bile transportation, but inherited problems and certain drugs can also cause it.

In this article, we’re giving you a review about bilirubin blood tests, when they are recommended, and what doctors will do with them.

What is Bilirubin?

Bilirubin is a pigment found in the blood with an orange-yellow color. However, it is not meant to give color to body fluids. It is actually a waste product that results from the breakdown of a protein known as heme. This protein is an essential part of hemoglobin, the carrier inside red blood cells that transports oxygen from the lungs to other tissues.

Red blood cells typically last in the blood for around 120 days. After that, they slowly lose their function and need to be replaced. When red blood cells are too old, they are destroyed, and new red blood cells take their place. Bilirubin is a waste product that results from this process. After being released in the blood, it is detected and processed by the liver and then removed by casting it into the gastrointestinal system.

There are two primary forms of bilirubin, and they are both measured in lab tests:

  • Unconjugated bilirubin: It is the raw material, so to speak. When heme proteins are broken down, unconjugated bilirubin is immediately released. This type of bilirubin travels attached to sugar in the blood. Then, the molecules are detected and caught by the liver.
  • Conjugated bilirubin: It is bilirubin that has already been processed by the liver. It would immediately pass to the gallbladder and then drained as bile into the small intestines in normal circumstances. Blood levels are very low in normal circumstances.

Written by Martin Davis