Bilirubin is the product that is formed from further breakdown of heme. As a waste product, bilirubin is secreted into bile and is also what gives urine it's yellow color. Additionally, yellow bruises obtain their color also from bilirubin in a condition called jaundice. Since bilirubin is a breakdown from hemoglobin, it is generated in large quantities as red blood cells undergo turnover. Phagocytes then absorb the dead red blood cells where it is converted into free bilirubin and then released into plasma and eventually absorbed by liver cells. Finally, bacteria in the intestine metabolizes bilirubin where it is eliminated as urine or feces, which is also one of the reasons for its brown color.
Bilirubin Blood Test
As the name suggests, the bilirubin test measures the amount of bilirubin in a blood sample usually taken from a heel stick for a baby or from the vein for an adult. The reason for this test is because it can be used to check for liver function and watch out for early signs of liver disease, diagnose conditions that affect the destruction of red blood cells, or to find out if something blocking
Conditions that may affect the test are caffeine, which can lower bilirubin levels, and fasting, which increases bilirubin levels.
"Biliary Excretion of Waste Products: Elimination of Bilirubin." About.com: Biology. N.p., n.d. Web. 5 Dec. 2012. <http://biology.about.com/library/organs/bldigestliver4.htm>.
Pope, John. "Bilirubin." WebMD. Healthwise, 13 May 2010. Web. 5 Dec. 2012. <http://www.webmd.com/digestive-disorders/bilirubin-15434>.