Bilirubin and Biliverdin - Meaning, Difference Between Them

Bilirubin is a yellowish-coloured pigment and a metabolite of heme. It is formed due to the breakdown of the red blood cells. 

Once the lifecycle of the red blood cells is complete, the haemoglobin present in them undergoes degradation, where the biliverdin formed undergoes further reduction to give bilirubin as an end product.

Accumulation of the bilirubin in the body tissues can be a warning sign of a liver condition. High or increased bilirubin levels in the body can cause serious conditions like hyperbilirubinemia and jaundice. 

There are two types of bilirubin which include:

1. Unconjugated bilirubin (Indirect Bilirubin) :  This type of bilirubin is formed when the red blood cells break down, which travels in the blood and into the liver. Unconjugated or indirect bilirubin is insoluble in water and is extremely toxic to the body. A spike in unconjugated bilirubin can cause unconjugated hyperbilirubinemia.
2. Conjugated bilirubin (Direct Bilirubin) : When unconjugated bilirubin is conjugated by the addition of glucuronic acid, conjugated or direct bilirubin is formed. Conjugated or direct bilirubin is easily soluble in water and is non-toxic to the body. Increased conjugated or direct bilirubin levels in the body lead to conjugated hyperbilirubinemia.

A spike in bilirubin may be due to various liver problems or other medical conditions. Depending on the symptoms, the doctor will examine and diagnose the cause leading to a high bilirubin level.