The body produces bilirubin when it breaks down red blood cells, and the liver helps excrete it. High bilirubin levels in adults can result from liver disease, pancreatitis, some cancers, and other health problems.

Elevated bilirubin can lead to jaundice, which causes yellowing of the skin and eyes. High bilirubin levels can occur in adults and newborns.

In adults, jaundice is usually caused by a medical condition. This is called pathologic jaundice and is more severe. In 75% of jaundice cases in newborns, the cause is physiologic or non-pathologic.

The skin normally becomes yellow once levels reach over 3 mg/dL. Any person who experiences yellowing of the skin or eyes should see a doctor. It may be a sign of a serious condition.

This article defines bilirubin and examines the causes of elevated bilirubin levels in adults and newborns. It also looks at the symptoms and treatment options for high bilirubin levels.

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The breakdown of red blood cells (RBCs) in the body produces bilirubin.

The RBCs have a lifespan of around 120 days, and they renew continually. RBCs contain hemoglobin, which helps transport oxygen around the body.

The process of removing iron from each cell’s hemoglobin helps the cells break down into bilirubin and other substances.

Bilirubin is transported to the liver by albumin, a simple protein. Liver cells absorb bilirubin, which then undergoes several chemical processes.

Once in the liver, bilirubin becomes “conjugated.” This means it is water-soluble, and the body can excrete it. The body ultimately expels bilirubin through stool. Bilirubin is brown and yellow, and it is this pigment that makes feces brown.

Unconjugated bilirubin is toxic. Conjugated bilirubin is usually not because it can come out of the body as long as nothing interferes with its removal.

High levels of bilirubin in the blood is known as hyperbilirubinemia. Elevated bilirubin levels can cause jaundice. Jaundice makes the skin and the whites of the eyes appear yellow, due to the brown and yellow bilirubin in the blood.

A doctor can usually detect a person’s bilirubin levels through a blood test. In adults, the approximate normal range of bilirubin in the blood is less than 1.0 milligram per deciliter (mg/dL).

Several conditions can cause high bilirubin levels before reaching the liver, after leaving the liver, or within the liver itself.

Before reaching the liver

Some conditions cause elevated bilirubin levels before it reaches the liver.

This is the pre-hepatic or the “pre-liver” phase. The cause is hemolytic anemia and the reabsorption of internal pools of blood by the body.

Hemolytic anemia occurs when too many red blood cells break down before their natural life cycle ends.

In the liver

If the liver is not working as it should, it may be unable to make bilirubin water-soluble. This may result in too much bilirubin building up in the liver.

Causes for this include:

After leaving the liver

Once bilirubin has left the liver, in the “post-hepatic phase,” its levels may be elevated because it is unable to leave the body.

This may result from a blockage in one of the other organs that assist excretion, such as from gallstones in the gallbladder.

Other causes may include inflammation or cancer of the gallbladder, or pancreatitis.

Gilbert’s syndrome

Gilbert’s syndrome is a mild form of high bilirubin. The levels go up and down because Gilbert’s syndrome slows down the process of removing it from the body.

The fluctuation is rarely enough to cause the skin to yellow, but some people may experience symptoms such as stomach pain or fatigue.

Doctors estimate that about 1 in 3 people with Gilbert’s syndrome do not experience any symptoms at all. In fact, doctors often discover the condition with a blood test performed for some other reason.

There is a gene linked to Gilbert’s syndrome that shows family patterns of heredity. This gene codes for an enzyme that enables the liver to convert bilirubin to its conjugated form. The absence of this gene in Gilbert’s syndrome means that this enzyme does not work.

Newborns with elevated levels of bilirubin have a condition that doctors call neonatal hyperbilirubinemia or jaundice in neonates.

A doctor generally considers anything above these values to be elevated:

1 day1.4–8.7 mg/dL
1–2 days 3.4–11.5 mg/dL
2–5 days 1.5–12.0 mg/dL
Over 5 days 0.3–1.2 mg/dL

According to a 2023 overview of research, approximately 50% of full-term infants and 80% of preterm infants have visible jaundice in the first 2–4 days after birth if their serum bilirubin levels are at or above 5 mg/dL.

In adults, bacteria in the gut break down the conjugated bilirubin to create a by-product called urobilinogen, some of which is excreted by the kidneys as urobilin. The urobilin is also what gives urine its yellow color.

In neonates, the liver takes several days to start adequately processing bilirubin. Neonatal jaundice occurs when the liver is not quite ready to process the bilirubin, and the accumulation in the blood causes certain tissues to look yellow.

Are elevated bilirubin levels in newborns a cause for concern?

The seriousness and medical significance of elevated bilirubin will depend on the cause. The infant’s age, as well as whether they were born premature, is also a factor.

Doctors need to distinguish whether the cause is pathologic or non-pathologic. Doctors consider jaundice in newborns to be pathologic if:

  • jaundice is present on the first day of life
  • bilirubin levels rise by 5 mg/dL per day or more per day, or more than 0.2 mg/dL per hour
  • jaundice is present for over 2–3 weeks

For premature infants, the earlier the delivery occurs in the gestation period, the lower the threshold at which health professionals consider bilirubin levels to be excessive.

High bilirubin levels can be toxic to the nervous system and cause brain damage. However, most jaundice in infants is not severe, and the symptoms resolve naturally.

Prolonged jaundice is more common in infants who are breastfeeding. This type of jaundice is usually not harmful but requires close monitoring. The neonatal doctor might recommend seeing a lactation consultant, among other treatments if they diagnose jaundice.

Some infants receive phototherapy, where a physician exposes the baby to a special kind of blue-green light. This is a standard treatment in which the light converts the bilirubin to a different form that the liver and kidneys can remove.

High levels of bilirubin in the blood can cause jaundice, which may cause symptoms such as:

Because an underlying condition, such as liver disease or hemolytic anemia, may cause high bilirubin levels, a person may also experience other symptoms, including:

Blood tests can measure bilirubin levels.

In adults, a healthcare professional will collect a blood sample via a needle from a vein in the arm.

A healthcare professional will collect a blood sample in newborns via a heel-prick. In some cases, they may instead place a device called a transcutaneous bilirubin meter on the skin. However, this may still need to be followed up with a blood test.

A doctor will often request a bilirubin blood test alongside other laboratory tests to assess the function of the liver.

Other tests may include:

  • further blood tests to assess liver function and test for hepatitis, if indicated
  • a physical exam, where a doctor may feel the abdominal area to see if the liver is swollen or tender
  • imaging tests to visualize the liver, which might include an ultrasound, computerized X-ray with a CT scan, or high-powered images with an MRI scan
  • endoscopic retrograde cholangiopancreatography if imaging tests suggest there is an obstruction of the bile duct or pancreatic duct
  • an endoscopy to look at the ducts in which the bile travels to the gut
  • a liver biopsy, while uncommon, involves a small sample of liver tissue evaluated at a lab

Treatment depends on the underlying cause of the high bilirubin. If the cause is known, a person might remove bilirubin through treatment or lifestyle changes, such as avoiding alcohol.

Infants may need phototherapy, which helps the liver break down bilirubin using a special type of blue-green light, to treat their high bilirubin levels.

An exchange transfusion may also be necessary to remove the blood through a thin plastic tube and replace it with blood from a suitable donor.

Here are some common questions about high bilirubin levels.

Is high bilirubin life threatening?

High levels of bilirubin are often a symptom of another underlying health condition, which can range in terms of severity and prognosis.

In infants, high levels of bilirubin in the blood can lead to serious complications if left untreated, including kernicterus, a condition that can lead to brain damage, intellectual disabilities, and issues with hearing or vision.

Who is at a higher risk for elevated bilirubin levels?

According to a 2023 review, newborns and older adults are at a higher risk for developing jaundice caused by elevated bilirubin levels. However, the prevalence of specific causes of elevated bilirubin can also vary depending on several factors, including age and sex.

What does it mean to have elevated bilirubin with normal liver enzymes?

If a person has normal levels of liver enzymes, it may mean that there is another condition contributing to the elevated bilirubin levels besides liver disease.

However, keep in mind that a person can still have liver damage with normal liver enzyme levels, so it is best to talk with a medical professional to determine the cause and best course of treatment.

When the RBCs break down, they produce bilirubin. Usually, the body removes excess levels of bilirubin via stool and urine. However, elevated bilirubin levels can occur when it is unable to leave the body.

This can happen due to a variety of medical conditions, such as liver disease, pancreatitis, and other health problems.

Doctors usually request blood tests to test for elevated bilirubin levels, and the treatment a person requires will depend on the underlying cause.