Bilirubin is a yellowish pigment that plays a crucial role in understanding your liver health and overall wellbeing. If your doctor has recommended a bilirubin test, or you have noticed it as part of your liver function test results, you may be wondering what exactly this substance is and why measuring it matters. This comprehensive guide will explain everything you need to know about bilirubin testing, from the procedure itself to interpreting your results.
What is Bilirubin?
Bilirubin is a yellow-orange compound that forms naturally in your body as a byproduct of the breakdown of red blood cells. When red blood cells reach the end of their lifespan (approximately 120 days), they are broken down, releasing haemoglobin. This haemoglobin is then converted into bilirubin through a series of chemical reactions.
There are two main forms of bilirubin that are measured in blood tests:
Unconjugated (Indirect) Bilirubin – This is the initial form of bilirubin created when red blood cells break down. It is not water-soluble and travels through the bloodstream attached to a protein called albumin. This form cannot be easily eliminated from the body.
Conjugated (Direct) Bilirubin – When unconjugated bilirubin reaches the liver, it undergoes a process called conjugation, where it is combined with glucuronic acid. This makes it water-soluble, allowing it to be excreted into bile and eventually eliminated from the body through the digestive system.
The total bilirubin measurement on your blood test represents the sum of both conjugated and unconjugated bilirubin.
Why is a Bilirubin Test Performed?
A bilirubin test is commonly ordered as part of a comprehensive liver function panel, but there are several specific reasons your healthcare provider might request this test:
If you are interested in understanding more about how blood tests work generally, our guide on the procedure, results and after effects of blood testing provides helpful information.
The Bilirubin Test Procedure
A bilirubin test is a straightforward blood test that requires minimal preparation. Here is what you can expect:
Before the Test
In most cases, no special preparation is needed for a bilirubin test. However, you should inform your healthcare provider about any medications or supplements you are taking, as some can affect bilirubin levels. If your test is part of a broader liver function panel, you may be asked to fast for 8-12 hours beforehand.
During the Test
The blood sample is collected through a simple venipuncture procedure. A healthcare professional will clean an area on your arm, typically the inside of your elbow, and insert a small needle into a vein. The blood is collected into one or more tubes, and the entire process takes just a few minutes. You may feel a brief pinch when the needle is inserted.
After the Test
Once the blood is drawn, pressure is applied to the site, and a small plaster is placed over it. You can resume normal activities immediately. Some people may experience minor bruising at the puncture site, which typically resolves within a few days.
Understanding Your Bilirubin Results
When you receive your bilirubin test results, you will typically see values for total bilirubin, and possibly separate values for direct (conjugated) and indirect (unconjugated) bilirubin. Understanding these numbers is key to interpreting your liver health.
Normal Bilirubin Levels
Normal reference ranges can vary slightly between laboratories, but generally fall within these parameters:
It is important to note that reference ranges may differ based on the laboratory and testing methods used. Always compare your results to the specific reference range provided on your report.
What High Bilirubin Levels May Indicate
Elevated bilirubin levels, known as hyperbilirubinaemia, can result from various conditions depending on which type of bilirubin is elevated:
High Unconjugated (Indirect) Bilirubin:
High Conjugated (Direct) Bilirubin:
When both types are elevated, it often suggests a more generalised liver problem affecting multiple processes. For a deeper understanding of liver health markers, you may find our article on liver function tests helpful.
What Low Bilirubin Levels May Indicate
Low bilirubin levels are generally not a cause for concern and are rarely clinically significant. In fact, some research suggests that slightly lower bilirubin levels may be associated with reduced antioxidant protection, as bilirubin has been found to have some antioxidant properties. However, this is an area of ongoing research and low levels alone typically do not indicate any health problems.
Conditions Associated with Abnormal Bilirubin
Jaundice
The most visible sign of elevated bilirubin is jaundice, characterised by yellowing of the skin and the whites of the eyes. Jaundice occurs when bilirubin levels exceed approximately 35-50 µmol/L. In addition to the yellow discolouration, you may notice dark urine (due to excess bilirubin being excreted by the kidneys) and pale, clay-coloured stools (due to lack of bilirubin reaching the intestines).
Gilbert Syndrome
This is a common and benign genetic condition affecting approximately 3-7% of the population. People with Gilbert syndrome have reduced activity of the enzyme that conjugates bilirubin, leading to mildly elevated unconjugated bilirubin levels. The elevation is usually harmless and may fluctuate, often becoming more noticeable during fasting, illness, stress, or menstruation.
Liver Disease
Various liver conditions can affect bilirubin processing. Hepatitis (viral, alcoholic, or autoimmune), cirrhosis, and liver cancer can all impair the liver's ability to conjugate and excrete bilirubin. Monitoring bilirubin levels alongside other liver markers provides valuable information about liver function.
Factors That Can Affect Your Results
Several factors can influence your bilirubin test results:
When to Seek Medical Advice
While we provide your raw bilirubin test data at Private Blood Tests London, we recommend sharing your results with your GP or healthcare provider for proper interpretation. You should seek medical advice promptly if you experience:
Bilirubin Testing as Part of Comprehensive Health Monitoring
A bilirubin test is most valuable when interpreted alongside other blood markers. At Private Blood Tests London, bilirubin is included in our liver function test panel, which also measures enzymes such as ALT, AST, ALP, and GGT, as well as proteins like albumin. Together, these markers provide a comprehensive picture of your liver health.
Learn about [decoding your liver function tests](/blog/decoding-your-liver-function-tests-lfts), [liver health and what blood tests reveal](/blog/liver-health-matters-what-blood-tests-can-reveal-about-this-vital-organ), and explore our [liver function test services](/liver-function-test).
Regular health screening can help detect changes in your bilirubin levels over time, allowing for early identification of potential issues. If you are interested in taking a proactive approach to your health, explore our health screening packages or book a liver function test at our CQC-registered clinic in South Kensington.
Conclusion
Understanding your bilirubin test results is an important step in monitoring your liver health and overall wellbeing. While elevated or abnormal levels can indicate various conditions, they must always be interpreted in the context of your complete health picture, symptoms, and medical history.
At Private Blood Tests London, we make it easy to access bilirubin testing and comprehensive liver function panels. Our experienced team ensures a comfortable testing experience, and your results are delivered quickly and securely. For interpretation and any follow-up care, we recommend consulting with your GP or healthcare provider who can advise on the best course of action based on your individual circumstances.