Serum bilirubin levels vary among different ethnicities and infant maturation levels, but concern for bilirubin toxicity occurs when the bilirubin level is above 25 mg per dL, states American Family Physician. When hemolysis in the term newborn is present, a bilirubin level above 20 mg per dL is a concern.
Bilirubin toxicity occurs when bilirubin crosses the blood-brain barrier before the bilirubin reaches the liver. In newborns, the bilirubin level is frequently above 5 mg per dL without any complications, reports American Family Physician. As the level rises, the risk of neurological damage increases. Early effects of bilirubin toxicity include poor feeding, hypotonia and lethargy. Late effect symptoms are demonstrated after the first week of life and include irritability, seizures, apnea and hypertonia. Chronic encephalopathy may develop, causing cerebral palsy, hearing loss and even mental retardation.
Elevated bilirubin levels of 5 mg to 6 mg per dL are common in newborns. It is considered pathological if jaundice emerges within the first 24 hours, the bilirubin levels increase by 5 mg per dL a day, or if the bilirubin level is greater than 17 mg per dL, according to American Family Physicians. Treatments such as phototherapy exist to decrease bilirubin levels and prevent bilirubin toxicity.