Bilirubin is a bile pigment that is orange-yellow in color. It is formed during the normal breakdown of red blood cells (hemoglobin), and is excreted in the bile. Bilirubin can be classified as indirect while it is circulating in the body. In this form it may also be termed "free" or "unconjugated bilirubin. Bilirubin can be classified as direct after conjugation in the liver with glucuronic acid. This form may also be termed "conjugated bilirubin. The reference range of total bilirubin is 0.2-1.2 mg/dL. The reference range of direct bilirubin is 0.1-0.4 mg/dL.