The first thing to know about how to sign up for Medicare is that some people don't have to do anything at all, while others have to apply themselves. Which group you're in depends on one fact: whether Social Security was already paying you well before your 65th birthday. This guide walks through how to tell which path is yours, how to apply through the Social Security Administration if you need to, and what you choose along the way.
Start here: are you automatic, or do you apply?
Before you do anything, settle one question, because it decides everything that follows. Were you already receiving Social Security or Railroad Retirement Board (RRB) benefits at least four months before you turn 65? If so, your enrollment is handled for you. If not (and that includes claiming Social Security only a month or two before your birthday), you have to apply, and the window to do it on time is narrow.
If Social Security started at least four months before 65, you're automatic
If you started collecting Social Security or RRB benefits at least four months before you turn 65, the government enrolls you in Medicare automatically. If you claim Social Security later than that, you are not auto-enrolled and have to apply yourself. That trap is worth knowing, because waiting for a card that isn't coming is how people miss their enrollment window. The automatic path also covers you if you're under 65 and have received Social Security Disability Insurance (SSDI) for 24 months. If you're in one of those groups, you don't fill out anything.Centers for Medicare & Medicaid Services. (n.d.). How do I sign up for Medicare?. medicare.gov. Retrieved Jul 15, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/sign-up/how-do-i-sign-up-for-medicare
Your red, white, and blue Medicare card arrives in the mail about three months before your coverage starts, which works out to roughly three months before the month you turn 65, or before your 25th month of SSDI benefits. When it shows up, you'll already be signed up for both Part A (hospital) and Part B (medical), with coverage starting the first day of the month you turn 65. One carve-out: in Puerto Rico, automatic enrollment gives you premium-free Part A only, and you have to actively enroll in Part B yourself.
There's one decision the automatic path still leaves to you. Because Part B carries a monthly premium, you're allowed to decline it. Most people shouldn't. If you turn down Part B and do not qualify for a Special Enrollment Period or a Medicare Savings Program, you can owe a late penalty that adds 10% to your premium for each full 12-month period you could have had Part B but didn't, and it follows you for as long as you have Part B. You'll also wait for a later enrollment window to pick it up. The most common Special Enrollment Period is the one for people still working with employer coverage, covered below. Creditable drug coverage is what excuses the Part D penalty, not the Part B one.Centers for Medicare & Medicaid Services. (n.d.). Avoid late enrollment penalties. medicare.gov. Retrieved Jul 15, 2026, from https://www.medicare.gov/basics/costs/medicare-costs/avoid-penalties
How to sign up for Medicare if you're not automatic
If you're approaching 65 and haven't started Social Security, the responsibility is yours. The Social Security Administration handles the application, and you have three ways to do it. Online is the fastest, but all three reach the same place.
| How to apply | What you do | Good to know |
|---|---|---|
| Online | Go to ssa.gov/medicare/sign-up and complete the application | Fastest option; you'll need a free "my Social Security" account, which takes a few minutes to set up |
| By phone | Call 1-800-772-1213 (TTY 1-800-325-0778) | SSA now points people to this line to get help or set up an appointment rather than to walk in; expect a wait at busy times |
| In person | Visit a local Social Security office | Best if you have questions or documents to bring; make an appointment first rather than dropping in |
Through any of these, you're applying for Part A and Part B together, or for Part A alone. Apply during the three months before your birthday month and your coverage can begin the first day of the month you turn 65. The full set of windows, including what happens if you miss this one, is covered in our guide to Medicare enrollment periods.Centers for Medicare & Medicaid Services. (n.d.). How do I sign up for Medicare?. medicare.gov. Retrieved Jul 15, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/sign-up/how-do-i-sign-up-for-medicare
What you'll need on hand
You don't need much, but having it ready makes the application go quickly. Gather your Social Security number, your birth certificate or other proof of birth, and proof of U.S. citizenship or lawful residence if you weren't born here. If you're delaying because you have job-based coverage, you'll later need your employer to complete CMS-L564 (Request for Employment Information), confirming when that coverage started and ended. SSA will tell you exactly what applies to your situation as you go.
After Parts A and B: the choices you make separately
Signing up through SSA gets you Original Medicare, Parts A and B. It does not, on its own, give you prescription drug coverage, an out-of-pocket cap, or the extras some plans offer. Those come from separate enrollments you handle after your Part A and B are in place, and you make them with the plans and insurers directly rather than through SSA.
You have a few directions to go from here:
- Add a Part D drug plan. Original Medicare doesn't cover most outpatient prescriptions, so most people enrolled in Parts A and B add a standalone Part D plan. You can compare plans and enroll using Medicare's Plan Finder at medicare.gov/plan-compare.
- Or switch to a Medicare Advantage plan. Instead of Original Medicare, you can choose a Medicare Advantage (Part C) plan, which bundles Parts A and B and usually drug coverage into one private plan. You enroll through the plan, also using the Plan Finder.
- Consider Medigap if you keep Original Medicare. A Medigap (Medicare Supplement) policy pays the deductibles and coinsurance Original Medicare leaves to you. You buy it from an insurer, not from SSA. Your best shot at any policy regardless of health is the six-month Medigap Open Enrollment Period that opens once you're both 65 and enrolled in Part B: during it, an insurer must sell you any policy it offers, can't use medical underwriting to turn you down over a pre-existing condition, and can't charge you more because you have health problems.Centers for Medicare & Medicaid Services. (2025). Choosing a Medigap Policy: A Guide to Health Insurance for People with Medicare (CMS/NAIC, 2025) - Medicare.gov. medicare.gov. Retrieved Aug 22, 2026, from https://www.medicare.gov/publications/02110-choosing-a-medigap-policy.pdf
Deciding between Original Medicare plus Medigap and a Medicare Advantage plan is the bigger fork in the road, and it shapes your costs and which doctors you can see. Our guide to Original Medicare vs. Medicare Advantage lays out that comparison.
How to sign up for Medicare if you're still working at 65
Plenty of people keep working past 65 and stay on a health plan from a current employer, either their own or a spouse's. As long as the group coverage is based on that current employment, you can delay Part B without a penalty and sign up later, when the job or the coverage ends. Not every job-based plan counts: Medicare gives this guidance for group health insurance that is available to everyone at the company, and tells people who are self-employed, or whose plan is not available to everyone at the company, to ask their insurance provider whether it is employer group health plan coverage as the IRS defines it, and to sign up at 65 if it is not. This Special Enrollment Period does not apply if you're eligible for Medicare based on End-Stage Renal Disease (ESRD).Centers for Medicare & Medicaid Services. (n.d.). When does Medicare coverage start?. medicare.gov. Retrieved Aug 9, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start
When that happens, you get an eight-month Special Enrollment Period (SEP) to enroll without penalty. CMS counts those eight months from the month the job ends or the coverage ends, whichever comes first, and Social Security counts from the month after, so count from the earlier one. Coverage under this Special Enrollment Period generally starts the first month after you sign up. If you sign up for Part B while you're still working, or within the first full month after the employer coverage ends, you can ask to delay your Part B start date up to 3 months.Centers for Medicare & Medicaid Services. (n.d.). When does Medicare coverage start?. medicare.gov. Retrieved Aug 9, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start Here's the trap worth knowing now: COBRA and retiree coverage do not count as current-employer coverage for this purpose, so neither one extends that window. If you're relying on COBRA after leaving a job, the Special Enrollment clock may already be running.Centers for Medicare & Medicaid Services. (n.d.). When does Medicare coverage start?. medicare.gov. Retrieved Aug 9, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start Our guide to how Medicare works with other insurance explains the timing in detail before you make a decision you can't undo.
Part D runs on a different clock, and this is where the costly mistake happens. That eight-month Special Enrollment Period covers Part B and premium Part A only. It does not extend your Medicare drug coverage deadline. Part D has its own trigger: a late enrollment penalty applies once you go 63 days or more without creditable drug coverage. Employer drug coverage often is creditable, and your plan must tell you in writing whether yours is, so keep that notice. But if you assume the eight months covers Part D too and let more than 63 days pass, the penalty is added to your Part D premium for as long as you have Part D.Centers for Medicare & Medicaid Services. (n.d.). When does Medicare coverage start?. medicare.gov. Retrieved Aug 9, 2026, from https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start
Frequently Asked Questions
Do I sign up for Medicare through Medicare or through Social Security?
Through Social Security. The Social Security Administration processes Medicare enrollment for Parts A and B, even though the program itself is Medicare. You can apply online at ssa.gov/medicare/sign-up, by phone at 1-800-772-1213, or at a Social Security office. The official walkthrough also lives on the Medicare page covering how to sign up.
When should I apply if I'm not automatically enrolled?
Apply during the three months before the month you turn 65. Doing it in that window means your coverage can start the first day of your birthday month, with no gap. You can also sign up during the month you turn 65 or the three months after, but coverage then starts a little later.
How do I know if I'll be enrolled automatically?
If you started receiving Social Security or Railroad Retirement Board benefits at least four months before you turn 65, you're enrolled automatically and your card arrives by mail. If you're under 65 and have gotten SSDI for 24 months, you're also enrolled automatically. If you haven't started Social Security, or you start it inside those last four months, you must apply yourself.
Can I sign up for just Part A and skip Part B?
Yes, you can take premium-free Part A and turn down Part B. But unless you qualify for a Special Enrollment Period (a current employer's plan is the usual route) or for a Medicare Savings Program, declining Part B can mean a lifelong late penalty when you do enroll. Think carefully before skipping it.
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The information on Brevy.com is for educational purposes only and is not a substitute for professional legal, financial, or medical advice. Rules vary by state and program and change frequently. Always verify with the relevant agency or a qualified professional. Brevy is not a law firm, financial advisor, or healthcare provider.