What is Bilirubin?

Red cells are replaced continuously, so bilirubin is being made all the time and the liver has to keep clearing it. What ends up in blood therefore depends on two things: how fast red cells are breaking down, and how well the liver and bile ducts carry the pigment away. One bilirubin figure cannot say which of the two has changed.

Haemoglobin and Haematocrit describe the red cell pool bilirubin is made from. ALP comes from the cells lining the ducts that carry it away. A change in bilirubin while both of those hold steady points instead to the liver's own handling of the pigment.

Faster red cell breakdown, as in haemolysis, raises the pigment load, and a blockage in the bile ducts slows its exit. A day or two without food raises bilirubin as well.

The liver clears bilirubin within hours, so a cause that has passed leaves no trace by the next day. A yearly measurement therefore tests whether the liver is still clearing the pigment as fast as it is made. This is Do Health's monitoring schedule, not a general recommendation for everyone.