What could be the cause of abnormally high bilirubin levels?

High billirubin. Elevation of billirubin can be caused production. Accelerated breakdown of red blood cells. Liver disease one of many functions is to remove from blood stream. Blocked excretion billirubin should be deposited in gall bladder as bile salts any thing blocking exit can raise billirubin. I have simply covered about a couple hundred disease conditions. Need to consult your doctor.