AMT Phlebotomy Practice Exam

Phototherapy works by using blue light to convert bilirubin into water-soluble isomers that the body can excrete more easily without needing further conjugation by the liver. When phototherapy is effective and the infant is exposed adequately, a substantial portion of the bilirubin pool can be cleared in a short time. In many clinical situations, about half of the bilirubin concentration decreases after one hour of light exposure, assuming good light intensity and exposure. The exact amount can vary based on how strong the light is, how much skin is exposed, the distance from the skin, and the starting bilirubin level. So, roughly a 50% decrease after one hour is a commonly cited expectation.