It depends. If you’re receiving benefits from Social Security or the Railroad Retirement Board (RRB) at least four months before you turn 65, you do NOT need to sign up; you’ll automatically get Part A and Part B starting the first day of the month that you turn 65. You should receive your Medicare card in the mail three months before your 65th birthday. If you are NOT receiving benefits from Social Security or the RRB at least four months before you turn 65, you will need to sign up with Social Security to get Parts A and B. To sign up to receive Parts A and B, you can enroll online with Social Security, call Social Security at 1-800-772-1213, or visit your local Social Security office.