The Relationship Between Biliverdin and Bilirubin

Bilipigments—including biliverdin and bilirubin—are inevitable byproducts of red blood cell metabolism in the human body. Upon red blood cell rupture, hemoglobin is released and converted into heme, which then undergoes a series of enzymatic reactions to ultimately form bilirubin. Biliverdin, as a precursor to bilirubin, is reduced to bilirubin by specific enzymes. Bilirubin is the primary pigment component of bile, imparting an orange-yellow color; approximately 250–350 mg of bilirubin is produced daily in the human body, with the majority derived from hemoglobin degradation in senescent red blood cells. Under normal physiological conditions, these bilipigments are excreted from the body via bile. However, certain gastrointestinal disturbances—such as abdominal chilling or intestinal infection—may cause biliverdin in the stool to be excreted before it is fully reduced to bilirubin, resulting in green-colored stools.