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Bilirubin Blood Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Bilirubin Blood Test

A bilirubin blood test measures the levels of bilirubin in your blood to help evaluate liver health, diagnose jaundice, or monitor liver disease.

What is a bilirubin blood test?

A bilirubin blood test measures the levels of bilirubin in your blood. Bilirubin is a yellowish substance made during your body's normal process of breaking down old red blood cells. It is found in bile, a fluid your liver makes to help you digest food.

If your liver is healthy, it will remove most of the bilirubin from your body through your bile ducts (the tubes that carry bile from your liver). If your liver is damaged or your bile ducts are blocked, bilirubin can leak out of your liver and into your blood. When too much bilirubin gets into the bloodstream, it can cause jaundice, a condition that causes your skin and eyes to turn yellow. If you have jaundice, your health care provider may order a bilirubin blood test to check for liver disease or damage.

Bilirubin is usually tested with a blood test but can also be tested in your urine.

What is it used for?

A bilirubin blood test may be used to check the health of your liver, look for the cause of jaundice, or determine how well a treatment is working. The test is also commonly used to help diagnose newborn jaundice. While many healthy babies develop jaundice because their livers haven't developed enough to get rid of the bilirubin, high levels can lead to brain damage, so infants are often tested as a precaution.

Why do I need a bilirubin blood test?

Your health care provider may order a bilirubin blood test for the following reasons:

  • If you have symptoms such as jaundice, dark urine, clay-colored stool, or stomach pain, which could indicate hepatitis, cirrhosis, or other liver diseases.
  • To find out if there is a blockage in your bile ducts.
  • To monitor an existing liver disease.
  • To diagnose disorders related to your body breaking down red blood cells too quickly, such as hemolytic anemia.

What happens during a bilirubin blood test?

A health care professional will take a blood sample from a vein in your arm using a small needle. You may feel a little sting when the needle goes in or out, and the process usually takes less than five minutes. If the test is done on a newborn, they will have a heel stick test, where a professional cleans the heel, pokes it with a small needle, and collects a few drops of blood.

Will I need to do anything to prepare for the test?

Your provider may tell you to fast (not eat or drink) for several hours before your blood test. You may also need to stop taking certain medicines, so tell your provider about everything you take. Do not stop taking any medicines unless your provider tells you to.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

The results will show if the amount of bilirubin in your blood is in the normal range. If the results are outside your lab's reference range, you may need further testing.

High bilirubin levels (hyperbilirubinemia) may be due to:

  • Hemolytic anemia
  • Liver disease
  • Blockage in your bile ducts

Low bilirubin levels (hypobilirubinemia) are not usually a cause for concern but may be due to medicines such as antibiotics, birth control pills, sleeping pills, and seizure medicines.

Abnormal results don't always mean you have a medical condition that needs treatment, as higher-than-normal levels can be caused by some medicines, certain foods, or strenuous exercise.

Is there anything else I need to know about a bilirubin blood test?

A bilirubin blood test is only one measure of your liver health. If your provider suspects a liver disease or a red blood cell disorder, you may need other tests, such as:

  • Liver function tests
  • Liver protein tests
  • Urine tests
  • An ultrasound
  • A liver biopsy

Frequently Asked Questions

In newborns, bilirubin testing is often done via a simple skin test called transcutaneous bilirubinometry, which uses a small device to measure light reflection from the skin without a needle. If levels are high, a blood test is confirmed. This is critical because infant livers are immature and can struggle to clear bilirubin, leading to jaundice. Unlike adults, where high levels usually point to liver disease or blockage, high levels in babies can lead to brain damage if not treated promptly with phototherapy, making early and frequent monitoring essential in the first few weeks of life.
Yes, certain medications and supplements can interfere with bilirubin levels or the accuracy of the test. For example, some antibiotics, diuretics, and high doses of vitamin C can potentially affect how bilirubin is measured or metabolized. It is important to provide a complete list of all prescription drugs, over-the-counter medications, and herbal supplements you are taking to your healthcare provider before the test so they can interpret the results accurately and rule out medication-induced changes.
No, fasting is generally not required for a standard bilirubin blood test. You can eat and drink normally before the appointment unless your healthcare provider gives you specific instructions otherwise. However, if the test is part of a broader liver function panel that includes lipid or glucose measurements, your provider may ask you to fast for 8 to 12 hours. Always confirm with your clinic to ensure you follow the correct protocol for your specific order.
High bilirubin levels indicate that your body is not processing or excreting bilirubin efficiently, which can result from liver damage, bile duct obstruction, or excessive breakdown of red blood cells. While mild elevations can sometimes be due to benign conditions like Gilbert syndrome, which is a common genetic trait that does not require treatment, significantly high levels often signal serious issues such as hepatitis, cirrhosis, or gallstones. Your provider will interpret these results alongside other liver enzymes and symptoms to determine the cause and severity.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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