Since you are already getting Social Security benefits, you are automatically enrolled in Medicare A and B when you turn 65. Medicare Part A hospital insurance is free for most people and cannot be declined unless you’re willing to give up your monthly Social Security benefits. You can, however, opt out of Part B—and its monthly fee of $185 for people with a modified adjusted gross income of $106,000 or less—by signing the back of the Medicare card and checking the box indicating “I do NOT want Part B (Medical Insurance).”