An overview of bilirubin
A bilirubin test measures the levels of bilirubin in your blood. Bilirubin is a yellowish pigment that is made during the breakdown of red blood cells. Higher than usual levels of bilirubin may indicate liver or bile duct problems. Bilirubin testing is usually done to investigate jaundice, determine bile duct blockage, detect liver disease, evaluate anemia or drug toxicity, and monitor treatments. The test is performed using a blood sample, and results are typically expressed as direct, indirect, or total bilirubin.
What is bilirubin used for?
Bilirubin testing is done to measure the levels of bilirubin in the blood. Bilirubin is a yellowish pigment that is made during the breakdown of red blood cells. Higher than usual levels of bilirubin may indicate different types of liver or bile duct problems. Bilirubin testing is usually one of a group of tests to check the health of your liver. It may be done to investigate jaundice, determine whether there might be blockage in your bile ducts, help detect liver disease, evaluate anemia caused by the destruction of red blood cells, or monitor the progression of a treatment. The test is done using a blood sample, and results are expressed as direct, indirect or total bilirubin.
How is bilirubin conducted?
A bilirubin test is conducted by obtaining a blood sample from a vein in the arm or a heel stick in newborns. The blood is sent to a laboratory for analysis, and the results are expressed as direct, indirect, or total bilirubin. Typical results for total bilirubin are 1.2 mg/dL for adults and 1 mg/dL for those under 18, while direct bilirubin results are generally 0.3 mg/dL. These values may vary slightly based on the laboratory, the individual's age and sex, and other factors.
How are bilirubin results reported?
Bilirubin test results are typically reported as total bilirubin or direct bilirubin. Total bilirubin is the sum of direct and indirect bilirubin, and it's the most common result reported. Direct bilirubin refers to the part of bilirubin that is bound to the albumin in the blood. Normal ranges for total bilirubin are around 1.2 milligrams per deciliter (mg/dL) for adults and 1 mg/dL for those under 18. Normal ranges for direct bilirubin are generally around 0.3 mg/dL. However, these values can vary slightly between laboratories and may be influenced by factors such as recent physical activity, certain foods, or medications. Therefore, it's important to inform your healthcare provider about any relevant details before the test.
Understanding the report
Bilirubin test results are typically interpreted based on the levels of direct and total bilirubin in the blood.
- Total bilirubin: This is the sum of direct and indirect bilirubin. Normal total bilirubin levels are usually 1.2 milligrams per deciliter (mg/dL) for adults and 1 mg/dL for those under 18. Elevated levels may indicate liver or bile duct problems, or an increased rate of red blood cell destruction.
- Direct bilirubin: This is the portion of bilirubin that is filtered through the liver. Normally, direct bilirubin levels are around 0.3 mg/dL. Higher levels may indicate liver damage or disease.
- Indirect bilirubin: This is the portion of bilirubin that isn't filtered through the liver. Elevated levels may be caused by other factors, such as Gilbert's syndrome or hemolysis.
It's essential to consider other factors that may affect the test results, such as food, medications, or strenuous exercise. Always inform your healthcare provider about your activity levels and any consumed food or medications before the test.
Limitations and Considerations
The bilirubin test is a useful tool for evaluating liver function and detecting potential issues. However, there are some limitations to the test:
- It only measures bilirubin levels, which may not provide a complete picture of liver health. Additional tests, such as liver function tests, are often needed to assess liver function comprehensively.
- Bilirubin levels can be influenced by factors other than liver or bile duct problems, such as blood transfusions, certain medications, or hemolysis (breakdown of red blood cells). Therefore, interpreting the test results may require consideration of other clinical information and context.
- The test may not always accurately detect or diagnose specific liver diseases or conditions. Additional tests and evaluations may be necessary for a definitive diagnosis.
- The test may not be suitable for individuals with certain medical conditions that affect bilirubin levels, such as severe sepsis, shock, or hemolysis. In these cases, alternative tests may be required for assessing liver function.
- Results may vary between laboratories, and the reference ranges provided may not be applicable to all populations. It is important to discuss your individual results with your healthcare provider to understand their significance in your specific case.