I llnoked this up a little while ago on the NSW industrial relations website, and it sort of implied sick leave could be used to take time off if you are sick, or if you are looking after a sick relative. It didnt say anything about using sick leave for attending doctors visits. It might be up to your employer whether they want to allow you to use sick leave for that or not.
This was just in the general leave info section, so it might be different if you are on a specific award?