If a medical issue comes up during the semester (i.e. might need surgery) how does UNC handle medical leave? Can you defer acceptance to a different semester or do they offer other options like online options?
A lot depends on the timing. For a non-mental health medical issues, it should be rather straight forward. Apply for a leave and return when you have medical clearance. I believe you will need to reapply but if you are a student in good standing that should not be an issue. If properly done, the courses for that semester will not appear on your transcript. If you are close to the end of the semester than you might have the option to take an incomplete and work with the professors and school to complete the course. I doubt online courses will be an real option but others can comment.
For mental heath leaves, the process is similar but different. They are not treated the same.
There could be ramifications for financial aid. You could have to pay back some of your federal aid. You will need to discuss this with the FA department. Also you will lose some or all of what you have paid for the semester.
Did you have a specific question?