Everything you need to know about bilirubin and newborns 2026

Labilirubin is a yellowish substance found in the blood. It is formed after red blood cells are broken down, and travels through the liver, gallbladder and finally the digestive tract, before finally being excreted through feces.

The medical condition of having high levels of bilirubin is known as hyperbilirubinemia, and is quite common among newborns. In fact, many babies are often born with high bilirubin, causing a condition called jaundice of the newborn (physiological jaundice).

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What is newborn jaundice?

Newborn jaundice, also known medically as physiological jaundice, is a condition that occurs when a baby has a high level of bilirubin in the blood, resulting in two very obvious symptoms: both their skin and eyes tend to turn yellowish.

This is an extremely common condition, usually caused by two reasons. The most normal is due to the - common - existence of a newborn's liver that is still immature, as it is an organ that is still developing, so it is not capable of metabolizing it well.

Added to this is that most neonates have a large number of red blood cells (or red blood cells). Some of these red blood cells are usually destroyed two or three days after birth, causing bilirubin to increase.

That is, the newborn's still developing liver may not yet be mature enough to be able to eliminate excess bilirubin, especially if some of the red blood cells present in large quantities after birth tend to be destroyed after two or three days.

For this reason, it is very common for newborn jaundice to appear two or three days after birth.

Breastfeeding may also be related. It occurs in 10 percent of newborns, and is due to the presence in breast milk of a substance that blocks the elimination of bilirubin.

However, it is not harmful, and this does not mean - obviously - that breast milk is bad for the newborn (quite the opposite!). However, when it occurs, it usually starts between 4 to 7 days, and lasts between 3 to 12 weeks.

How is excess bilirubin in the newborn treated?

The good news is that, in most cases, newborn jaundice tends to go away on its own as the baby's liver matures and develops; especially when the little one begins to feed, which helps bilirubin pass through the body until it is eliminated through feces.

Therefore, in most cases, jaundice usually disappears within 2 to 3 weeks. However, if after this time it remains and does so for more than 3 weeks, it may be a symptom of the existence of an underlying condition.

In addition, high levels of bilirubin in the blood can put the baby's health at risk, potentially attacking the brain and producing a disease known as kernicterus, which would lead to mental retardation by putting the baby at risk of deafness, cerebral palsy or other forms of brain damage.

We must keep in mind that bilirubin is destroyed by light. Therefore, when it is detected in time, the baby is usually placed in a special crib or incubator to place it under light sources. Furthermore, so that the light does not damage the eyes, they usually remain blindfolded for the entire duration of the treatment.

Thanks to the action of these foci, the high - and worrying - level of bilirubin in the blood of the newborn begins to acquire normal values. And, once the jaundice is overcome, the child will not suffer from it again.

For all these reasons, newborns are examined for jaundice before hospital discharge, and again between 3 to 5 days after discharge, in this case by the midwife or by the pediatrician at the child's first check-up after leaving the hospital.