The timing of the appearance of jaundice helps with the diagnosis.
Jaundice appearing in the first 24 hours is quite serious and usually requires immediate treatment.
When jaundice appears on the second or third day, it is usually "physiologic." However, it can be a more serious type of jaundice.
When jaundice appears on the third day to the first week, it may be due to an infection.
Later appearance of jaundice, in the second week, is often related to breast milk feedings, but may have other causes.
Laboratory testing for hyperbilirubinemia may include:
- Direct and indirect bilirubin levels: These levels reflect whether the bilirubin is bound with other substances by the liver so that it can be excreted (direct), or is circulating in the blood circulation (indirect).
- Red blood cell counts
- Blood type and testing for Rh incompatibility (Coombs' test)