What is the definition or description of: total bilirubin?

See answer details.: Bilirubin, a product of hemoglobin breakdown, is present in two forms in the human body: unconjugated (indirect bilirubin, insoluble) and conjugated (direct bilirubin, soluble). Unconjugated bilirubin is conjugated in the liver and released into the small intestine in bile, the fluid in the gallbladder. Total bilirubin measures indirect bilirubin plus direct bilirubin; part of a liver test panel.