When a baby is born, one of the first things doctors check is the baby’s skin and eyes for signs of jaundice. Jaundice is a yellowing of the skin and eyes that happens when there is too much bilirubin in the blood. Most newborns have mild jaundice, which is common and usually harmless. However, if bilirubin levels become too high, it can be dangerous and even life-threatening.
This guide explains what bilirubin is, why levels can rise in newborns, what counts as a dangerous level, and how doctors treat and prevent complications.
Understanding Bilirubin
Bilirubin is a yellow pigment that forms when the body breaks down old red blood cells. Normally, the liver filters bilirubin out of the blood and removes it through the stool.
In newborns, this process often takes time to mature. Their livers are still developing, and their red blood cells break down faster than those of adults. As a result, bilirubin can build up in the baby’s body and cause jaundice, making the baby’s skin and eyes look yellow.
Why Newborns Have Higher Bilirubin Levels
Newborns naturally produce more bilirubin than adults because:
- They have more red blood cells. Babies are born with a high number of red blood cells, which break down quickly after birth.
- Their liver is immature. The newborn liver is not yet efficient at removing bilirubin.
- They pass stool less often at first. Bilirubin leaves the body through stool, and if a baby is not feeding or passing stool well, bilirubin can build up.
For most babies, this mild increase is temporary and harmless. The yellow color usually appears around the second or third day of life and fades within one to two weeks.
Types of Jaundice in Newborns
Not all jaundice is the same. Doctors look at the timing, cause, and severity to determine whether it is normal or dangerous.
1. Physiological jaundice – This is the most common type. It happens in most healthy babies and appears after 24 hours of life. It usually peaks around day 3 to 5 and fades without treatment.
2. Breastfeeding jaundice – This type occurs in the first week when the baby is not getting enough breast milk. Less feeding means less stool, and bilirubin stays longer in the body.
3. Breast milk jaundice – Some babies develop jaundice after the first week due to substances in breast milk that slow bilirubin processing. It is usually mild and harmless.
4. Hemolytic jaundice (due to blood group incompatibility) – This happens when the mother’s and baby’s blood types are incompatible (such as Rh or ABO incompatibility). The baby’s red blood cells break down quickly, raising bilirubin levels sharply. This type can be severe and needs medical attention right away.
5. Other medical causes – Premature birth, infections, liver disease, or enzyme deficiencies can also raise bilirubin levels and make jaundice more serious.
What Is a Dangerous Level of Bilirubin?
The definition of a dangerous level depends on several factors, including the baby’s age in hours, weight, and health condition.
Doctors measure bilirubin in milligrams per deciliter (mg/dL) or micromoles per liter (µmol/L). The safe and dangerous ranges vary with time after birth because bilirubin naturally rises in the first few days.
Here is a general guide for term babies (born after 37 weeks):
| Baby’s Age | Typical Bilirubin Level (mg/dL) | Risk Level |
| Less than 24 hours | Below 5 | Usually normal |
| 24–48 hours | Up to 10 | Often normal but should be watched |
| 49–72 hours | Up to 12–15 | May still be normal in some babies |
| Over 72 hours | Above 15 | Needs attention and possible treatment |
| Any time | Over 20 | Considered dangerous |
For premature babies, the dangerous threshold is lower, often above 10–15 mg/dL, because their brains and livers are more fragile.
Why High Bilirubin Levels Are Dangerous
When bilirubin levels become too high, it can cross into the brain tissues. This condition is called kernicterus, a rare but serious type of brain damage caused by excess bilirubin.
Kernicterus can lead to:
- Permanent brain injury
- Hearing loss
- Developmental delays
- Muscle stiffness or paralysis
- Learning problems later in life
That is why doctors carefully monitor bilirubin levels in newborns, especially during the first few days after birth.
Signs That Bilirubin Levels Might Be Too High
It can be difficult for parents to know how high bilirubin is just by looking at the baby, but there are warning signs that need medical attention:
- Yellow skin spreading from the face to the chest, arms, legs, and soles of the feet
- Yellowing of the whites of the eyes
- Baby is very sleepy or hard to wake
- Refusal to feed or poor sucking
- Weak or high-pitched cry
- Arching of the back or neck
- Unusual limpness or stiffness
If any of these signs appear, parents should contact their doctor right away or go to the emergency room.
How Bilirubin Levels Are Checked
Doctors use one of two methods to measure bilirubin:
- Transcutaneous bilirubin test (TcB): A light sensor is placed on the baby’s skin to estimate bilirubin levels. It is quick, non-invasive, and often used for screening.
- Blood test (Total Serum Bilirubin, TSB): A small blood sample gives an exact measurement. This test is used when jaundice appears early, looks severe, or when TcB readings are high.
The doctor then plots the bilirubin result on a bilirubin nomogram, a chart that shows normal and dangerous ranges based on the baby’s age in hours. This helps determine whether treatment is needed.
How Doctors Treat High Bilirubin Levels
Treatment depends on how high the bilirubin level is and how fast it is rising. The main goal is to lower bilirubin safely and prevent brain damage.
1. Phototherapy
This is the most common treatment. The baby is placed under special blue lights that change bilirubin into a form that can be removed through urine and stool.
- The baby wears only a diaper, and the eyes are protected.
- Phototherapy can last from several hours to a few days.
- The treatment is safe and effective in most cases.
If bilirubin levels drop to normal, phototherapy can be stopped.
2. Exchange transfusion
If bilirubin is extremely high and does not respond to phototherapy, the baby may need an exchange transfusion. In this procedure, the baby’s blood is replaced with donor blood in small portions to quickly remove bilirubin.
This is a rare treatment used only when the risk of brain injury is high.
3. Treating underlying causes
When jaundice is due to another condition like blood incompatibility or infection, the doctor will treat that cause as well. For example:
- Giving IV fluids for dehydration
- Treating infections with antibiotics
- Giving special immune globulin (IVIG) for Rh or ABO incompatibility
When Parents Should Worry
Most cases of jaundice are mild and go away with time or light therapy. However, parents should seek help if:
- The yellow color appears within the first 24 hours of life
- The baby’s skin looks more yellow than before
- The baby is feeding poorly or not gaining weight
- The baby seems weak, floppy, or hard to wake
- The yellow color spreads to the arms, legs, or palms and soles
- The baby is born early (before 37 weeks)
- There is a family history of severe jaundice or blood type incompatibility
Doctors often ask parents to return for a follow-up bilirubin test within a few days after discharge, especially if the baby was born early or showed mild jaundice before going home.
Can Dangerous Bilirubin Levels Be Prevented?
In many cases, yes. Parents and healthcare providers can work together to prevent bilirubin from reaching dangerous levels.
1. Ensure proper feeding
Frequent feeding helps bilirubin leave the body through stool. Newborns should feed 8 to 12 times a day in the first week.
- Breastfed babies may need extra help latching.
- Formula-fed babies should feed regularly to stay hydrated.
2. Follow-up visits
Schedule follow-up checkups within a few days after birth to check for jaundice. This is especially important if the baby was discharged early.
3. Know your baby’s risk
Babies at higher risk include:
- Premature infants
- Babies with blood type differences from the mother
- Babies with siblings who had severe jaundice
- Babies who are bruised at birth or have cephalohematoma (a scalp swelling with blood)
If your baby has any of these risk factors, your doctor will monitor bilirubin closely.
4. Keep an eye on changes at home
Parents should watch their baby’s skin color under natural light. Gently pressing on the skin can help reveal yellowing. The doctor can advise when a bilirubin test is needed.
Bilirubin Levels by Risk Zone
Pediatricians often classify bilirubin readings into risk zones based on age in hours and bilirubin value. These zones guide treatment decisions.
| Risk Zone | Bilirubin (mg/dL) | Meaning |
| Low Risk | Below 10 | Usually safe |
| Low-Intermediate Risk | 10–14 | Watch closely, may need recheck |
| High-Intermediate Risk | 14–18 | Possible phototherapy |
| High Risk | Above 18–20 | Needs immediate treatment |
Each hospital may have slightly different cutoffs, but these levels give a general idea of when bilirubin becomes dangerous.
How Long Does Jaundice Last?
In most healthy full-term babies, jaundice appears around day 2, peaks at day 3–5, and disappears by the second week.
In premature babies, it can last longer, sometimes up to three weeks.
If jaundice lasts more than two weeks in full-term babies or three weeks in premature babies, it may be due to another cause like:
- Liver disease
- Blocked bile ducts
- Thyroid issues
- Infection
In such cases, the doctor will do further tests to find the cause.
Long-Term Outlook
When treated early, even high bilirubin levels usually leave no lasting problems. Most babies recover fully with normal growth and development.
However, untreated severe jaundice can cause permanent brain damage or hearing loss. That is why timely diagnosis and treatment are so important.
What Parents Can Expect During Treatment
If your baby needs treatment in the hospital:
- You can usually stay nearby and continue feeding the baby.
- Nurses will check bilirubin levels every few hours.
- The baby may need extra fluids to prevent dehydration during phototherapy.
- The light treatment might make your baby’s stool more frequent and loose, which is normal.
Once bilirubin levels fall to a safe range, the baby can go home, but follow-up visits may be scheduled to ensure it does not rise again.
Home Phototherapy
For babies with moderate jaundice, doctors sometimes recommend home phototherapy. Parents rent or borrow a special light blanket or pad that delivers safe light therapy while allowing normal feeding and bonding.
The doctor will monitor bilirubin levels with regular blood tests or home nurse visits to make sure the treatment is working.
Frequently Asked Questions
1. Is mild jaundice harmful?
No, mild jaundice is very common and usually harmless. It just means the baby’s body is adjusting after birth.
2. Can breast milk cause jaundice?
Breast milk itself does not cause dangerous jaundice. Some babies develop mild, longer-lasting jaundice related to substances in breast milk, but it is usually not harmful.
3. What if my baby looks yellow but acts normal?
You should still tell your doctor. A simple test can show whether bilirubin levels are safe.
4. Can sunlight help lower bilirubin?
Gentle exposure to natural light can help, but it should not replace medical treatment. Direct sunlight can harm a baby’s delicate skin.
5. When should I go to the hospital?
If your baby is very yellow, hard to wake, not feeding well, or has any of the serious signs listed earlier, go to the hospital immediately.
Key Takeaways
- Bilirubin is a yellow substance formed when red blood cells break down.
- Jaundice happens when bilirubin builds up in a baby’s blood.
- A dangerous level is usually above 20 mg/dL in full-term babies and above 10–15 mg/dL in premature babies.
- High bilirubin can cause brain damage if not treated.
- Phototherapy is the most common and safe treatment.
- Feeding often, watching for signs, and keeping follow-up appointments can prevent problems.
Conclusion
Jaundice in newborns is common and usually nothing to worry about. Most babies recover on their own or with a short course of light therapy. The key is to keep a close eye on your baby’s color, feeding, and alertness during the first week after birth.
Knowing what levels of bilirubin are dangerous helps parents act early and prevent complications. With timely care and medical support, babies with high bilirubin levels can grow and thrive just like any other child.
