Bilirubin (direct)

The fraction of bilirubin the liver has already processed and is ready to send out in bile.

It is the half that says the problem is at or after the liver rather than before it, which is the split that matters most.

A raised direct fraction is the one worth taking seriously; it points at the liver or the bile ducts rather than at red cells. It also rules Gilbert syndrome out, because there the direct fraction stays normal.

Worth discussing any clearly raised value.