If you already get benefits from Social Security, you’ll get Medicare Part A and Part B automatically when you’re first eligible. You don’t need to sign up. Medicare will send you a “Welcome to Medicare” packet three months before you turn 65. You’ll still have other important deadlines and actions to take, so read all of the materials in the packet.
If you’re over 65 (or turning 65 in the next three months) and NOT already getting benefits from Social Security, you’ll need to sign up to get Medicare Part A (hospital insurance) and Part B (medical insurance). You won’t get Medicare automatically.