Farmer is absolutely correct - the FMLA you would take for appointments is called Intermittent Medical Leave and you can take it as needed and do not have to make up the time, by law. It does need to be for the particular condition you were approved for leave for. It is also illegal for your boss to give you a hard time about this. I'm not sure how large a company you work for, but I would go straight to Human Resources and get everyone on the same page.