Bilirubin is formed by the breakdown of red blood cells in the body. The liver helps to excrete it. The levels of bilirubin in the blood can indicate the health of the liver.
High levels of bilirubin can lead to jaundice. This disorder is easily recognizable due to a yellowing of the skin or eyes. The medical term jaundice comes from the French word for yellow, jaune.
High bilirubin levels can occur in adults, but the disorder is more common in newborns. This is because a baby has fewer bacteria in the gut to help break down and dispose of bilirubin.
The approximate normal range of bilirubin in the blood serum is:
- For adults, 1.2 milligrams per deciliter (mg/dL)
- For children under 18 years, usually 1 mg/dL
The skin normally becomes yellow when levels reach 3 mg/dL or more.
Anyone who gets yellowing of the skin or eyes should see their doctor. It may be a sign of a serious condition.
What is bilirubin?
Bilirubin is created by the breakdown of red blood cells (RBCs) in the body. The bilirubin travels to the liver, is secreted to the bile duct, and is ultimately excreted from the body in the stool. Bilirubin is brownish-yellow in color and it is this pigment that gives feces its brown color.
High levels of bilirubin can lead to yellowing of the eyes and skin.
The RBCs have a lifespan of around 120 days and they are continually renewed. Red blood cells contain hemoglobin and it is this that gets broken down into bilirubin and other substances. The bilirubin is carried to the liver by albumin.
Once in the liver, bilirubin gets “conjugated.” This means it becomes water-soluble and can be excreted.
Unconjugated bilirubin is toxic, but conjugated bilirubin is not because it is removed from the body.
High bilirubin levels
A high level of bilirubin in the blood is known as hyperbilirubinemia.
High bilirubin levels can cause jaundice. In a person with jaundice, the skin and the whites of the eyes look yellow because of the brownish-yellow bilirubin in the blood.
There are three main reasons why bilirubin levels can rise and lead to jaundice. These problems can happen before, during, or after the production of bilirubin.
Before reaching the liver
Some conditions can cause bilirubin levels to be high before it reaches the liver. This is called the pre-hepatic or “pre-liver” phase and it can be caused by hemolytic anemia and reabsorption of internal pools of blood. Hemolytic anemia happens when too many red blood cells are broken down.
In the liver
If the liver is not working properly, it may be unable to conjugate the bilirubin to make it soluble with water. This may result in too much bilirubin staying in the liver.
- Viruses, for example hepatitis A
- Medicines, including acetaminophen
- Autoimmunity, where a disorder of the immune system causes it to attack the body’s own cells
After leaving the liver
Once the bilirubin has left the liver, levels may be high because the bilirubin is unable to leave the body. This may be due to a blockage in one of the other organs that help with excretion such as gallstones in the gallbladder. This is called the post-hepatic phase.
Other causes include:
Blood and urine tests can measure bilirubin levels.
If a urine test detects bilirubin, a doctor will look at blood serum tests to confirm the results and see if there is any damage to the liver. If there is no bilirubin in the urine, doctors will check whether or not increased red cell breakdown is causing the problem.
Other tests include:
- Further blood tests to assess liver function.
- A physical exam, where a doctor may feel the abdominal area to see if the liver is enlarged or tender.
- Imaging tests to visualize the liver. These might include ultrasound, computerized X-ray with a CT scan, or high-powered images with an MRI scan.
- An endoscopy is sometimes carried out to look at the ducts in which the bile travels to the gut.
- A liver biopsy is sometimes needed, although this is very rare. In this procedure, a small sample of liver tissue is sent to a lab for evaluation.
Treatment of high bilirubin levels
A doctor will need to identify the cause of high bilirubin levels. Treatment depends on what the underlying cause of the high bilirubin is. If the cause is known, bilirubin may be removed through treatment or lifestyle changes, such as avoiding alcohol.
What is Gilbert’s syndrome?
Gilbert’s syndrome is a mild form of high bilirubin. The levels go up and down because the process of removing it from the body is slowed down.
The fluctuation is rarely enough to cause the skin to yellow, but some people may experience symptoms such as stomach pain or fatigue.
Gilbert’s syndrome is often discovered when a blood test is done 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 this enzyme does not work.
High bilirubin in newborn babies
Newborns with high levels of bilirubin have a condition that doctors call neonatal hyperbilirubinemia, or jaundice in neonates. The Merck Manual state that almost half of newborns have visible jaundice in the first week after birth.
High levels of bilirubin in newborn babies can be treated with phototherapy.
In adults, bacteria in the gut break down the conjugated bilirubin to create urobilin, and this is excreted in feces. In neonates, the lack of gut bacteria means this does not happen so effectively. Newborns also have an enzyme that may reabsorb unconjugated bilirubin, causing higher levels in the body.
The level of concern will depend on the cause. The age of the baby and whether it was born too soon are also factors. In a healthy infant born at full term, bilirubin levels tend to be of concern when they exceed around 18 mg/dL.
For premature infants, the threshold goes down the earlier the delivery.
High bilirubin can be toxic to nerves and lead to brain damage.
Treatment will address the underlying cause.
Most cases of jaundice in babies are not serious and the symptoms disappear naturally. However, jaundice is more common in breastfed babies, and a doctor may recommend that a mother stop breastfeeding.
Some babies are given phototherapy, where they are exposed to a special kind of fluorescent white light. This is a standard treatment in which the light converts the bilirubin into a different form that can be removed from the body by the liver and kidneys.