Is 2.3 serum bilurbin is high?

Depends on what: Units of measurement you are referring to. But if your total or direct bilirubin is measured in mg/dL, then 2.3 would be elevated; not significantly but still on the high side.

Hyperbilirubinemia: Yes, it is elevated..and several things can attribute to this. Alcoholic hepatitis, gallstones, cirrhosis, transfusion reactions and pancreatic cancers to name several causes. Gilbert's syndrome is a common, mild liver condition in which the liver doesn't properly process a substance called bilirubin. Bilirubin is produced by the breakdown of red blood cells.