It depends. Some people get Part A and Part B automatically, and some have to sign up. If you're already getting benefits from Social Security or the Railroad Retirement Board, you'll automatically get Part A and Part B starting the first day of the month you turn 65. If you're close to 65 but aren't getting those benefits, you'll need to sign up for Medicare.
What matters most
Automatic if you already get benefits
If you're getting benefits from Social Security (or the Railroad Retirement Board) at least 4 months before you turn 65, you'll automatically get Part A. You'll also be signed up for Part B, unless you live in Puerto Rico or outside the U.S.
Sign up yourself if you don't
If you're close to 65 but aren't getting Social Security or Railroad Retirement Board (RRB) benefits, you'll need to sign up for Medicare. You can apply for Part A and Part B at SSA.gov/medicare/sign-up, or contact Social Security 3 months before you turn 65 to set up an appointment.
Your card comes in the mail
If you get Medicare automatically, you'll get your red, white, and blue Medicare card in the mail 3 months before your 65th birthday or your 25th month of disability benefits. If you sign up yourself, Medicare mails you a welcome package with your Medicare card about 2 weeks after you sign up.
Want the detail? How it works, a worked example and common mix-ups are in .
Words on this page
Part A
the part of Medicare that helps pay for hospital and inpatient care
Part B
the part of Medicare that helps pay for doctor visits and outpatient care
Initial Enrollment Period
the 7 months around the month you turn 65 when you can first sign up for Medicare
Who can answer for your situation
You sign up for Medicare through Social Security: online at SSA.gov/medicare/sign-up, by phone at 1-800-772-1213, or through your local Social Security office. If you or your spouse worked for a railroad, call the Railroad Retirement Board at 1-877-772-5772.
The key is whether you're getting benefits from Social Security (or the Railroad Retirement Board) at least 4 months before you turn 65. If you are, you'll automatically get Part A and Part B starting the first day of the month you turn 65, unless you live in Puerto Rico or outside the U.S., where you aren't signed up for Part B. If your birthday is on the first day of the month, your Part A and Part B start the first day of the prior month.
Because you pay a monthly premium for Part B, you can choose whether to keep it or not. Most people choose to keep Part B. If you don't want Part B, let Medicare know before the coverage start date on your Medicare card. If you do nothing, you'll keep Part B and pay Part B premiums through your Social Security or RRB benefits.
How to sign up if it's not automatic
If you're close to 65 but aren't getting Social Security or RRB benefits, you'll need to sign up for Medicare. Medicare provides your coverage, but you'll sign up through Social Security (or the Railroad Retirement Board), because they need to see if you're eligible for Medicare. Signing up online at Social Security is the easiest and fastest way to sign up.
Your first chance to sign up is called your Initial Enrollment Period. It lasts for 7 months, starting 3 months before you turn 65 and ending 3 months after the month you turn 65. You can only sign up for Part B at certain times. If you don't sign up for Part B when you turn 65, you might have to wait to sign up and pay a monthly late enrollment penalty.
An example
Say you started getting Social Security benefits at 63. You'll automatically get Part A and Part B starting the first day of the month you turn 65. Now say you plan to wait until 67 to start Social Security, so you aren't getting benefits when you're close to 65. Then you'll need to sign up for Medicare yourself.
Still working at 65?
If you or your spouse are still working, you may be able to wait to sign up for Medicare without paying a late enrollment penalty.
Common mix-ups
These are the pairs people most often mix up.
Part B is a choice, but timing matters
Because you pay a monthly premium for Part B, you can choose whether to keep it or not. But you can only sign up for Part B at certain times. If you don't sign up for Part B when you turn 65, you might have to wait to sign up and pay a monthly late enrollment penalty.
Puerto Rico and outside the U.S.
If you live in Puerto Rico or outside the U.S. and get Social Security benefits, you get Part A automatically, but you aren't signed up for Part B. If you want Part B, you need to sign up for it.
1 What the source says · How do I sign up for Medicare? (introduction)
Some people get Medicare Part A (Hospital Insurance) and Part B (Medical Insurance) automatically, and some have to sign up for it.
Checked October 1, 2026
3 What the source says · Why do some people get Medicare automatically?
If you're getting benefits from Social Security (or the Railroad Retirement Board) at least 4 months before you turn 65, you'll automatically get Part A coverage. You'll also be signed up for Part B (unless you live in Puerto Rico or outside the U.S.).
Checked October 1, 2026
4 What the source says · Why do some people get Medicare automatically?
Because you pay a monthly premium for Part B coverage, you can choose whether to keep it or not.
Checked October 1, 2026
8 What the source says · Know when to sign up for Part B
You can only sign up for Part B at certain times. If you don't sign up for Part B when you turn 65, you might have to wait to sign up and pay a monthly late enrollment penalty.
Checked October 1, 2026
9 What the source says · Your answer: Contact Social Security to sign up for Medicare, Ways to sign up
Online (at Social Security) – It's the easiest and fastest way to sign up and get any financial help you may need.
Checked October 1, 2026
10 What the source says · Your answer: Contact Social Security to sign up for Medicare
About 2 weeks after you sign up, we'll mail you a welcome package with your Medicare card.
Checked October 1, 2026
11 What the source says · Why do I contact Social Security?
Medicare provides your coverage, but you'll sign up through Social Security (or the Railroad Retirement Board) because they need to see if you're eligible for Medicare
Checked October 1, 2026
15 What the source says · Sign up for Part B if you live in Puerto Rico or outside the U.S.
You get Part A automatically. If you want Part B, you need to sign up for it.
2 What the source says · Section 1: How Medicare works, Signing up for Medicare (p. 15)
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.
Checked October 1, 2026
5 What the source says · Section 1: How Medicare works, Will I have to sign up for Part A and/or Part B? (p. 15)
If you're close to 65, but AREN'T getting Social Security or RRB benefits, you'll need to sign up for Medicare. Visit SSA.gov/medicare/sign-up to apply for Part A and Part B. You can also contact Social Security 3 months before you turn 65 to set up an appointment.
Checked October 1, 2026
6 What the source says · Section 1: How Medicare works, Signing up for Medicare (p. 15)
If you get Medicare automatically, 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, and you don't need to pay a premium for Part A (sometimes called "premium-free Part A").
Checked October 1, 2026
7 What the source says · Section 1: How Medicare works, Signing up for Medicare (p. 15)
Most people choose to keep Part B. If you don't want Part B, let us know before the coverage start date on your Medicare card. If you do nothing, you'll keep Part B and pay Part B premiums through your Social Security or RRB benefits.
Checked October 1, 2026
14 What the source says · Section 1: How Medicare works, Signing up for Medicare (p. 15)
If your birthday is on the first day of the month, your Part A and Part B starts the first day of the prior month.
12 What the source says · Your first chance to sign up (Initial Enrollment Period)
This is called your Initial Enrollment Period. It lasts for 7 months, starting 3 months before you turn 65, and ending 3 months after the month you turn 65.
General education, not individualized advice. For your own situation, you can call 1-800-MEDICARE or your State Health Insurance Assistance Program (SHIP).
