Introduction to Bilirubin Bilirubin is a yellow compound that occurs naturally in the body as a byproduct of the normal breakdown of red blood cells. It is produced when hemoglobin, the substance in red blood cells that carries oxygen, is broken down into its components. This process occurs primarily in the liver, spleen, and bone marrow. During this breakdown, hemoglobin is split into heme and globin; the heme is further…