Red blood cells in the bloodstream live for approximately 120 days. When they age, red blood cells break down, and bilirubin is produced in the body as a result of this breakdown process. Every day, billions of red blood cells exit the body, and the same amount of new red blood cells are produced in bone marrow.
A molecule called haem plays a key role in the haemoglobin in red blood cells; oxygen circulating in the bloodstream binds to it. The haem that is produced when red blood cells break down cannot be reused, and the body has to get rid of it. The haem molecule forms bilirubin through breaking down. Free bilirubin is fat-soluble and does not dissolve in water. In the bloodstream, bilirubin binds to albumin (transport protein) and goes to the liver. It enters liver cells to be treated, and the liver cells conjugate the bilirubin with glucuronic acid. Bilirubin becomes soluble in water and is excreted in the bile. From there, its journey continues towards the gut and out of the body with faeces. Bilirubin is yellow, and it gives faeces its distinctive colour.
Bilirubin can therefore exist in three forms:
- Free bilirubin (approx. 90% of bilirubin) – in the bloodstream, soluble in fat, and can cause damage if it ends up in the brain
- Albumin-bound – bilirubin binds to albumin in the blood and is transported to the liver
- Conjugated bilirubin – bilirubin conjugates in the liver with glucuronic acid, becomes soluble in water, and is excreted in the bile
When is a good time to measure bilirubin levels?
A bilirubin test is a good idea in conjunction with the following symptoms:
- The whites of the eyes or the skin begin to turn yellow
- Urine is dark or faeces is of a clay grey colour
- Nausea and vomiting
- Stomach pain and/or bloating
- Fatigue and general malaise
In addition, bilirubin levels are examined as part of examining diseases of the liver and bile duct, possible anaemia, or yellowness in the newborn
How to interpret the bilirubin test result?
Normally, the result is:
- 5–25 umol/l
Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.
Read more about defining reference values.
What can cause elevated bilirubin values?
Bilirubin can become elevated through several mechanisms. The bilirubin concentration can increase due to decreased excretion of bilirubin, increased production, or both reasons at the same time.
If the passage of bile is obstructed and the bile cannot exit the gall bladder through the bile duct, bile accumulates in the liver cells and eventually some of it returns to the blood. The typical cause of an obstruction is a gallstone in the bile duct. A tumour in the pancreas or bile duct also obstructs the passage of bile.
High values also occur in connection with liver damage (hepatitis, liver necrosis) when liver cells are damaged. The functioning of sick cells is disturbed so much that passing the bilirubin to the gall bladder does not normally succeed. Liver damage can also be caused by some medicinal agents (e.g., antibiotics, oral contraceptives, non-steroidal anti-inflammatory drugs). In liver damage, it is typical that the concentrations of both overall bilirubin and conjugated bilirubin increase.
Excessive breaking down of red blood cells, haemolysis, increases the production of bilirubin and its concentration in blood. With increased haemolysis, the amount of free bilirubin in particular increases, and the liver cannot remove bilirubin at the same rate.
Newborn babies can have high bilirubin values because their capability to treat bilirubin is still insufficient.
What can cause decreased bilirubin values?
A level of bilirubin below the reference range is not connected to any disorder, so you should not worry about it.
The most typical additional bilirubin tests:
- Gamma-glutamyl transferase is a sensitive indicator of liver diseases (1489, S-GT)
- Alanine aminotransferase, indicator of liver cell damage (1026 S-ALAT)
- Aspartate aminotransferase reacts quickly to liver, cardiac muscle, and musculoskeletal cell damage (1128 S-ASAT)
- Alkaline phosphatase is elevated in liver and bone diseases (1046 S-AFOS)
SYNLAB test list: Bilirubin (1185 S-Bil, 4592 P-Bil) https://www2.synlab.fi/laboratoriokasikirja/tutkimuskuvaukset/bilirubiini/
SYNLAB tests: Bilirubin, bilirubin conjugates https://www.yml.fi/tuotekuvaus_show.php?tuotenro=54
Terveyskirjasto health library: Bilirubiini (P-Bil) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=snk03074&p_hakusana=bilirubiini
Hyvä Terveys: Seerumin bilirubiinipitoisuus https://www.hyvaterveys.fi/artikkeli/terveys/seerumin_bilirubiinipitoisuus
Lab Test online: Bilirubin https://labtestsonline.org.uk/tests/bilirubin
Fasting is not required
This examination does not require fasting