A high level of circulating bilirubin in a newborn, called hyperbilirubinemia, is commonly treated with:

1. Bilirubin, a byproduct of red blood cell breakdown, must be cleared by the liver and excreted in bile. 2. Newborns lack a fully functional blood-brain barrier, making high bilirubin levels particularly dangerous, since it is neurotoxic. 3. Breast milk's laxative properties help clear bilirubin through the stool, but if hyperbilirubinemia still develops, direct treatment is needed. 4. This treatment is phototherapy, because UV light helps break down bilirubin quickly. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 28 "Development and Inheritance", p.1353 §Changes in the Composition of Breast Milk_