If you had more than one student loan that you paid interest on and only entered one of them, the student loan interest deduction is limited to $2500. So if you have already entered $2500, you don't need to amend your return because you can't enter any more interest.
You don't deduct student loans per se. You can deduct qualified education expenses paid with student loans or out of pocket for education tax benefits unless you are claimed by someone else.
