<s>[INST] What is Bilirubin? [/INST] Bilirubin is a substance that is naturally formed in the liver when old red blood cells are broken down. It is a waste product and the liver functions to eliminate this waste from the body. Bilirubin is yellow in color and it is this that gives stool its usual color. Bilirubin is present in two important forms in body:

Indirect or Unconjugated Bilirubin: Bilirubin in this form flows freely in blood. It is insoluble and flows through the bloodstream and reaches the liver. When in liver, the bilirubin is changed into soluble form.
Direct or Conjugated Bilirubin: Bilirubin in this form is formed by the liver and is totally soluble in water. Direct bilirubin is derived from indirect bilirubin. Direct bilirubin is latched with other chemicals in liver and is secreted in bile that excretes it from body.
Liver functions to remove Bilirubin from the body, along with waste materials. However, when the body fails to remove this excess Bilirubin (a condition known as hyperbilirubinemia), it spreads to other nearby tissues and thus gives the yellowish tinge. Source: Medifee. Link: https://www.medifee.com/faq/Jaundice. Field: Hepatology . Disease: Jaundice </s>