Bilirubin is a yellow substance formed when red blood cells break down and is processed by the liver before being eliminated in stool and urine. Changes in bilirubin levels can indicate how well the liver and bile ducts are working.
High bilirubin levels may be linked to conditions like hepatitis, gallstones, blood disorders, or the use of certain medications. These changes can affect how bilirubin is processed or eliminated from the body.
When bilirubin builds up in the blood, it can cause symptoms such as yellowing of the skin and eyes, dark urine, and pale stools, known as jaundice. Bilirubin levels are measured through blood tests that assess total, direct, and indirect bilirubin to help identify the underlying cause.
Bilirubin blood test
Bilirubin can be assessed using the following blood tests:
-
Indirect bilirubin: Also called unconjugated bilirubin, this form is produced when red blood cells are broken down and is then carried to the liver.
-
Direct bilirubin: This form is made in the liver from indirect bilirubin, is joined to a sugar (conjugated), and is processed into bile so it can be removed from the body in stool and urine.
-
Total bilirubin: This measures the overall amount of bilirubin in the blood (both direct and indirect).
Bilirubin testing is usually done to assess how well the liver and bile ducts are working. It may also be ordered to check for conditions that affect red blood cells or cause them to break down.
Preparing for the test
In most cases, no special preparation is needed for a bilirubin test. Some labs may recommend fasting for about 4 hours before the exam. It is also important to inform the healthcare professional about any medications being taken, especially propranolol or rifampin, as they may affect the results.
Normal values
Normal bilirubin levels are generally:
In newborns, bilirubin levels can vary after birth. Higher levels are common in the first few days of life and usually begin to decrease after the fifth day.
Symptoms of high bilirubin
According to the NHS, jaundice from bilirubin buildup can cause symptoms such as:
- Yellowing of the skin
- Yellow eyes
- Itchy skin
- Dark urine that looks like cola
- Paler stools
Other symptoms may include abdominal pain, abdominal swelling, weakness, nausea, and vomiting. These symptoms are usually linked to problems affecting the liver, bile ducts, or blood.
Learn more about how to identify symptoms of liver disease and when to see a doctor.
Causes of high bilirubin
High bilirubin levels are usually caused by increased production or difficulty eliminating bilirubin from the body.
According to the NHS, jaundice can be caused by conditions such as hepatitis, gallstones, alcohol-related liver disease, pancreatitis, and sickle cell disease. The underlying cause depends on the type of bilirubin affected.
High direct bilirubin
High direct bilirubin is usually linked to conditions that make it harder for the body to eliminate bilirubin. This can happen with hepatitis, gallstones, primary sclerosing cholangitis, or narrowing of the bile ducts due to tumors or surgery.
Some medications, such as acetaminophen, antibiotics, and anti-inflammatory drugs, can also increase direct bilirubin levels, especially when used without medical guidance.
High indirect bilirubin
Indirect bilirubin levels can become high when red blood cells are destroyed faster than usual, as can happen with autoimmune hemolytic anemia, thalassemia, or hereditary spherocytosis. T
hey can also increase due to genetic conditions that affect how the liver processes bilirubin, such as Gilbert’s syndrome or Crigler-Najjar syndrome.
Certain medications, such as rifampin, gentamicin, and some antiretrovirals, may also increase indirect bilirubin levels, as can large bruises or blood transfusions.
High total bilirubin
High total bilirubin can result from elevated direct bilirubin, indirect bilirubin, or both. The cause varies and may include liver conditions like hepatitis or cirrhosis, certain medications, or blood disorders.
Low bilirubin
Low bilirubin levels are usually not a cause for concern. In healthy people, bilirubin is naturally processed and eliminated, so levels typically stay within the normal range.