Diseases & Conditions



Hyperbilirubinemia is an abnormally high level of bilirubin in the blood.

Aging red blood cells are removed by the spleen, and the hemoglobin from these red blood cells is broken down and recycled. The heme portion of the hemoglobin molecule is converted into a yellow pigment called bilirubin, which is carried in the blood to the liver where it is chemically modified and then excreted in the bile into the newborn's digestive tract. It is removed from the body when the newborn passes stools. Bilirubin in the stools of newborns gives them their yellow color.

In most newborns, the level of bilirubin in the blood increases in the first days after birth, causing the newborn's skin and the whites of the eyes to appear yellow (jaundice). If feedings are delayed for any reason, as occurs when newborns are sick or have a digestive tract problem, blood levels of bilirubin can become high. Also, breastfed newborns tend to have somewhat higher blood levels of bilirubin during the first week or two.

Hyperbilirubinemia may also occur when a newborn has a serious medical disorder, such as infection in the blood (sepsis). It may also be caused by hemolysis (rapid breakdown of red blood cells), as occurs with Rh incompatibility (see Pregnancy Complications: Rh Incompatibility ) or ABO incompatibility.

In the large majority of cases, elevated levels of bilirubin in the blood are not serious. However, very high bilirubin levels can produce brain damage (kernicterus). Very premature and critically ill newborns are at higher risk for developing kernicterus. In almost all cases, moderately elevated blood levels of bilirubin due to breastfeeding are not of concern. However, newborns who are slightly premature and are breastfeeding, especially if discharged early from the hospital, must be monitored closely for hyperbilirubinemia because they can develop kernicterus if the bilirubin level becomes very high.

Symptoms and Diagnosis

Newborns with hyperbilirubinemia have a yellow color to their skin and the whites of their eyes (jaundice). It may be more difficult to recognize jaundice in dark-skinned newborns. Jaundice usually first appears on the newborn's face and then, as the bilirubin level increases, progresses downward to involve the chest, abdomen, and finally the legs and feet.

Newborns with hyperbilirubinemia who are showing symptoms of kernicterus may become lethargic and feed poorly; these newborns should be examined immediately by a doctor. The later stages of kernicterus involve irritability, muscle stiffening or seizures, and a fever.

It is important that a doctor assess the degree of jaundice in all newborns during the first days of life. Some newborns have developed dangerously high levels of bilirubin after being discharged from the hospital on the first day after birth before their blood level of bilirubin had risen. Therefore, it is very important that newborns discharged early be examined at home by a visiting nurse or in the doctor's office within a few days after discharge to assess their bilirubin levels. This is especially true for newborns born a few weeks prematurely and those breastfeeding.

A doctor first examines the newborn under good lighting and then measures the level of jaundice by holding a specialized piece of equipment (bilirubinometer) against the newborn's skin or by testing a small sample of blood.


Mild hyperbilirubinemia does not require special treatment. Offering frequent feedings accelerates the passage of stools, thus reducing the reabsorption of bilirubin from the intestinal contents and lowering the bilirubin level. Moderate hyperbilirubinemia can be treated with phototherapy, in which the newborn is placed without clothes under fluorescent bilirubin lights. The light exposure alters the composition of the bilirubin in the newborn's skin, changing it to a form that is more readily excreted by the liver and kidneys. The newborn's eyes are shielded with a blindfold. Newborns can also be treated at home by having them lie on a fiber-optic "bilirubin blanket," which exposes their skin to bright light. These newborns need to have their blood levels of bilirubin tested repeatedly until they decrease.

Rarely, it may be necessary for a mother to change from breastfeeding to formula feeding temporarily to ensure that the newborn is obtaining adequate volumes with each feeding. The mother should resume breastfeeding as soon as the bilirubin levels start to decrease. Moderate hyperbilirubinemia sometimes continues for weeks in infants who are breastfed, a normal phenomenon that poses no problems for the infant and that does not usually require withholding of breastfeeding.

If the newborn's blood level of bilirubin approaches a dangerous level, it can be lowered rapidly by performing an exchange blood transfusion. In this procedure, a sterile catheter is placed into the umbilical vein located in the cut surface of the umbilical cord. The newborn's bilirubin-containing blood is removed and replaced with equal volumes of fresh blood.

Last full review/revision February 2003

Source: The Merck Manual Home Edition