Bilirubin is a yellowish pigment that is made during the body's normal process of breaking down old red blood cells. It is processed by the liver to be removed from the body. If your liver is healthy only small amounts of bilirubin are found in blood but if your liver isn't working properly bilirubin levels rise. This can cause jaundice, a condition that causes your skin and the whites of the eyes to become yellow.

Measuring bilirubin levels in the blood is used to diagnose and monitor liver disorders and is part of the Liver Function Tests panel, a group of tests that measure different liver substances. These tests are all performed on the same blood sample and give information about how your liver is working.

Bilirubin tests are also performed on newborn babies to monitor jaundice. Bilirubin tests are also used to help diagnose and monitor haemolytic anaemia, a disorder in which red blood cells are destroyed faster than they can be made and more rarely, to help detect certain rare genetic disorders in sick babies.

What is being tested?

Bilirubin is an orange-yellow pigment which is formed when haemoglobin, the red-coloured pigment of red blood cells that carries oxygen to tissues, breaks down. Bilirubin is ultimately processed by the liver to allow its elimination from the body. Small amounts of bilirubin are present in blood from damaged or old red cells that have died. If bilirubin levels increase in the blood, the appearance of jaundice becomes more evident.

How is it used?

When bilirubin levels are high, a condition called jaundice (a yellowing of the skin and the whites of the eyes) occurs and further testing is needed to determine the cause. Too much bilirubin may mean that too many red cells are being destroyed, or that the liver is incapable of removing bilirubin from the blood.

It is not uncommon to see high bilirubin levels (sometimes called neonatal bilirubin) in newborn babies (typically 2–7 days old). This transient condition is called physiological jaundice and resolves within a few days. Neonatal jaundice is likely to be abnormal if it persists longer than 8 - 14 days or if the conjugated bilirubin fraction is high. Then it could be caused by abnormal metabolism in the liver or malformation of the bile ducts. If the jaundice is present at birth and is caused by an elevated unconjugated bilirubin concentration, the newborn’s red blood cells may be being destroyed because of blood incompatibility between the baby and mother, called haemolytic disease of the newborn.

In adults or older children, bilirubin is measured to diagnose and/or monitor liver diseases (such as cirrhosis, hepatitis, or gallstones). Patients with sickle cell disease or other causes of haemolytic anaemia may have episodes where excessive red blood cell destruction takes place, increasing bilirubin levels.

When is it requested?

A doctor usually orders a bilirubin test in conjunction with other laboratory tests (alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase) for a patient who shows signs of abnormal liver function. A bilirubin level may be ordered when a patient:

• shows evidence of jaundice
• has a history of drinking excessive amounts of alcohol
• has suspected drug toxicity
• has been exposed to hepatitis viruses

Other symptoms that may be present include:

• dark, amber-coloured urine
• nausea/vomiting
• abdominal pain and/or swelling
• fatigue and general malaise that often accompany chronic liver disease
  Determining a bilirubin level in newborns with jaundice is considered standard medical care.

What does the result mean?

Newborns
Excessive bilirubin damages developing brain cells in infants and may cause mental retardation, physical abnormalities or blindness. It is important that bilirubin in newborns does not get too high. When the level of bilirubin is above a critical threshold, special treatment is used to reduce it. An excessive bilirubin level may result from the breakdown of red blood cells (RBCs) due to blood typing incompatibility between the mother and her newborn.

Adults and children
Doctors may request bilirubin tests (along with other tests, especially when jaundice is present) to determine if liver damage exists. Bilirubin levels can be used to monitor the progression of jaundice and to determine if it is the result of red blood cell breakdown or liver disease. This can be done by measuring two different chemical forms of bilirubin — direct (or conjugated) and indirect (or unconjugated) bilirubin. If the direct bilirubin is elevated there may be some kind of blockage of the liver or bile duct, perhaps due to gallstones, hepatitis, trauma, a drug reaction, or long-term alcohol abuse. If the indirect bilirubin is increased, haemolysis (undesirable breakdown of red blood cells) may be the cause.

Is there anything else I should know?

Although bilirubin may be toxic to brain development in newborns (up to the age of about 2 weeks), high bilirubin in older children and adults does not pose the same threat. In older children and adults, the 'blood-brain barrier' is more developed and prevents bilirubin from crossing this barrier to the brain cells. Elevated bilirubin levels in children or adults, however, strongly suggest a medical condition that must be investigated and treated.

Jaundice results from high levels of bilirubin. Increases in bilirubin may be due to metabolic problems, obstruction of the bile duct, infection, physical or chemical damage to the liver, or an inherited abnormality (Gilbert’s, Rotor’s, Dubin-Johnson or Crigler-Najjar syndromes).

Common questions

• Are some people more at genetic risk of abnormal bilirubin levels?

Several inherited conditions including Gilbert’s syndrome, Dubin-Johnson syndrome, Rotor’s syndrome and Crigler-Najjar syndrome can cause a raised bilirubin level. Of these four syndromes, Crigler-Najjar is the most serious. The first three are usually mild, long-term conditions that can be aggravated under certain conditions but in general cause no significant health problems.

• How do you treat abnormal bilirubin levels and/or jaundice?

Treatment depends on the cause of the jaundice. In newborns, phototherapy (special light therapy), blood exchange transfusion, and certain drugs may reduce the bilirubin level. In Gilbert’s, Rotor’s and Dubin-Johnson syndrome, no treatment is usually necessary. Crigler-Najjar syndrome may respond to certain enzyme drug therapy or may require a liver transplant. Jaundice caused by an obstruction, for example gallstones, is often resolved by surgery to remove the blockage. Jaundice due to cirrhosis is often a result of long-term alcohol abuse and may not respond well to any type of therapy, though abstaining from alcohol and ensuring good nutrition may improve the situation if the liver has not been damaged too badly.

• Is there anything I can do to maintain healthy bilirubin levels?

While there is no one specific thing, it is clear that excessive and long term alcohol consumption can lead to cirrhosis and a permanently damaged liver. Avoiding excessive alcohol consumption, drug toxicity and eating a proper diet can help sustain a healthy liver.

• What are the signs and symptoms of increased bilirubin levels?

The presence of jaundice, dark urine, pale stools and generalised itching may be found in obstructive jaundice.  More severe cases may include severe abdominal pain, anorexia, vomiting and fever.  Increased bilirubin levels may be a sign of another problem, such as cancer, and may be seen in conjunction with swollen glands or an enlarged spleen.

More information

RCPA Manual: Bilirubin- plasma or serum

RCPA Manual: Bilirubin- amniotic fluid

Healthdirect Australia: Jaundice