Total bilirubin

Bilirubin is a yellow pigment formed when the red blood pigment haemoglobin is broken down. Total bilirubin is measured in serum; it is made up of bilirubin not yet processed by the liver (indirect) and bilirubin already converted (direct). Its amount in the blood depends on how much is formed and how well the liver excretes it. The blood sample is taken in a practice. In the test catalogue the value is listed as “Billirubin gesamt” in the liver function profile.

What bilirubin does in the body

Red blood cells live for about 120 days. They are then broken down mainly in the spleen, and the haem part of haemoglobin is turned into bilirubin via the intermediate biliverdin. Bilirubin is fat-soluble and is carried to the liver in the blood bound to albumin. There the enzyme UGT1A1 attaches glucuronic acid, making bilirubin water-soluble so that it reaches the gut with the bile. Gut bacteria convert it into urobilinogen and stercobilin, which give faeces their brown colour; a small part is absorbed and colours the urine yellow. Bilirubin also acts as an antioxidant.

Low bilirubin – what happens in the body?

Low bilirubin values are generally unremarkable. Because bilirubin can neutralise free radicals, research is investigating whether low values go along with more oxidative stress. Studies have observed lower values in smokers and in people with cardiovascular disease, while people with the harmless Gilbert's syndrome and slightly raised bilirubin showed cardiovascular disease less often. Whether a low value plays a role of its own or merely reflects other influences has not been clarified.

Raised bilirubin – what happens in the body?

Bilirubin rises when more of it is produced or less is excreted. If more red blood cells are broken down (haemolysis), more indirect bilirubin is produced than the liver can process. In Gilbert's syndrome (Meulengracht's disease) the enzyme UGT1A1 works more slowly for inherited reasons; the value rises particularly during fasting, stress or infections and is harmless. If liver cells are damaged or bile becomes congested, for example due to gallstones, direct bilirubin passes into the blood: the skin and the whites of the eyes turn yellow, urine becomes dark, faeces pale, and congested bile acids can cause itching.

The interpretation is given in your report.