Direct (conjugated) bilirubin is a form of bilirubin that has been processed by the liver. When red blood cells break down, they produce bilirubin, which is initially unconjugated (indirect). This unconjugated bilirubin is transported to the liver, where it is conjugated (or bound) to glucuronic acid, making it water-soluble and allowing it to be excreted in bile and urine.
