If you’re already getting benefits from Social Security or the Railroad Retirement Board (RRB), you’ll automatically get Part A and Part B starting the first day of the month you turn 65. (If your birthday is on the first day of the month, Part A and Part B will start the first day of the prior month.)
If you’re under 65 and have a disability, you’ll automatically get Part A and Part B after you get disability benefits from Social Security or certain disability benefits from the RRB for 24 months.
If you have ALS (amyotrophic lateral sclerosis, also called Lou Gehrig’s disease), you’ll get Part A and Part B automatically the month your Social Security disability benefits begin.
If you’re automatically enrolled, you’ll get your red, white, and blue Medicare card in the mail 3 months before your 65th birthday or 25th month of disability benefits. If you do nothing, you’ll keep Part B and will have to pay Part B premiums through your Social Security benefits. You can choose not to keep Part B, but if you decide you want Part B later, you may have to wait to enroll and pay a penalty for as long as you have Part B.