My Good cholesterol low.

Has anyone had low good cholesterol. Mine is at 31 ( High Risk Is 45 Normal is 80. I have heart problems. Doctor said it is more than likly linked to that and my major life change. He told me to keep excercising and he would do more lab work in a few months., He said. As I lose weight it will more than likly go away. Does anyone know what this is all about. I think I had this before but it is called another name. Like eltrotrictes or something like that. Take Care Barb