Medicare open enrollment is generally for people who are already covered by Medicare and looking to review or change their plans. If you are about to turn 65, you can enroll in Medicare outside of the open enrollment period. Your seven-month enrollment window begins three months before the month of your 65th birthday, includes the month you turn 65, and ends three months after the month you turn 65. Once you have Part A and Part B coverage, you can decide if you want to enroll in a Medicare Advantage Plan or add a prescription drug plan to your coverage.