How Do Social Security and Medicare Work Together?

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6-minute read

Andy Markowitz and Phil Pruitt,

Updated September 26, 2025

AARP

Reviewed by

Jammie Lyell, M.S

En español

Published September 16, 2025

/ Updated September 26, 2025

You probably know that Social Security and Medicare intersect in some ways, but you might not be clear on exactly what.

Their relationship can be confusing because they are distinct programs. Yet Social Security and Medicare both serve older and disabled Americans.

Here is the crucial connection: Social Security handles enrollment for Medicare Part A hospital insurance and Part B medical insurance.

In this role, the Social Security Administration (SSA) works with the Centers for Medicare & Medicaid Services (CMS) to inform older Americans about their Medicare sign-up options, process their applications and collect some premiums.

How Social Security handles Medicare enrollment

Social Security is involved no matter when or how you enroll in Medicare.

If you’re already receiving Social Security retirement benefits at least four months before you turn 65, the SSA will send you a Welcome to Medicare package that includes your Medicare card at the start of your initial enrollment period, which begins three months before the month you turn 65. For example, if your 65th birthday is July 15, 2025, this period begins April 1.

On your 65th birthday, you’ll automatically be enrolled in parts A and B. You have the right to opt out of Part B, but you might face a penalty in the form of permanently higher premiums if you sign up for it later.

If your spouse is still working at a company with 20 or more employees and you get your health insurance that way, you can stay on your spouse’s plan until that coverage ends and save on Part B premium costs. But because you’ll get your Medicare card automatically as a retiree, you’ll need to follow the instructions in your Welcome to Medicare packet if you don’t want to keep Part B.

Don’t remove the card from the form you got in the mail. Check the box on the top right of the back of the form after “I DON’T want Part B (Medical Insurance),” sign your name and send back the entire form, including the card, in the enclosed envelope before the coverage start date on the front of the card.

Before you send it back, jot down your Medicare number so you’ll have it until you receive a new card in the mail from Social Security designating that you have only Part A.

65 and not yet retired? Apply for Medicare at SSA.gov

If you haven’t filed for Social Security benefits at least four months before age 65, you’ll need to apply for Medicare yourself.

You can do so any time during Medicare’s initial enrollment period, which lasts seven months. For that July 15 birthday, the sign-up window runs April 1 through Oct. 31. If you don’t enroll during that period, you could face those late fees if you do so in the future.

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You don’t have to sign up during your initial enrollment period if you or your spouse:

Are still working
Earned 40 work credits by paying Medicare taxes on your income for a total of 10 years.
Have private health insurance.
Expect to continue working in the near future.

You’ll probably want to get Part A because it’s free if you earned 40 work credits and can be a secondary hospital insurance to your private plan — unless you’re eligible for a health savings account and want to continue to contribute. But you can sign up at any time.

And you’ll be eligible for a special enrollment period later for Part B when your company-based insurance ends.

Once again, the Social Security Administration is at the center of the process. You’ll find comprehensive enrollment information in SSA’s Medicare booklet and links to application forms on the Social Security website.

How Medicare premiums are paid

If you are drawing Social Security benefits, your Medicare Part B premiums are deducted from your monthly payments. If you’re not getting benefits, you’ll receive bills from CMS.

Almost all Medicare beneficiaries pay no premiums for Part A because they worked and paid their 1.45 percent Medicare tax for 40 quarters, long enough to qualify for the program.

The standard Part B premium that most Medicare enrollees pay in 2025 is $185 a month. Also in 2025, the rate rises with a beneficiary’s income, going up in steps for individuals with incomes greater than $106,000 and married couples who file taxes jointly and have a combined income of more than $212,000.

And, yes, the Social Security Administration determines whether you will pay a higher premium based on income information it receives from the IRS.

Medicare tied to SSDI

People younger than 65 who are unable to work due to a serious injury or illness can qualify for Medicare if they are also receiving Social Security Disability Insurance (SSDI).

Like Social Security retirement benefits, SSDI is an earned benefit: You qualify by working and paying Social Security taxes. In addition, you must demonstrate that your medical condition largely prevents you from working and is expected to last at least one year or result in death.

SSDI recipients automatically qualify for Medicare 24 months after becoming entitled to disability benefits. The waiting period is waived for people with amyotrophic lateral sclerosis (ALS) or end-stage renal disease.

Medicare works for people with disabilities much as it does for eligible older adults. You likely won’t have to pay for Medicare Part A if you paid Medicare taxes while you were working. However, you will have monthly premiums for Part B, and for a Part D prescription drug plan if you enroll in one. These costs might be deducted from your SSDI benefit.

Medicare coverage linked to SSDI will end if benefits stop because your condition improves to the point that Social Security no longer considers you to have a disability. The SSA does periodic reviews to determine your medical eligibility for benefits.

SSDI also can end if, while still meeting the medical criteria for disability, you are able to work and your income exceeds a limit known as substantial gainful activity (SGA). In 2025, the limit is $1,620 per month, or $2,700 if you are blind. If you earn more, you can lose your benefits.

In that circumstance, however, you might not lose your Medicare. You may be able to extend coverage for up to seven years and nine months after your SSDI ends. That’s one of several work incentives Social Security offers to help disability beneficiaries return to the labor force.

Social Security–Medicare connection started in 1965

The relationship between Social Security and Medicare is rooted in history and reflected in the title of the legislation President Lyndon Johnson signed July 30, 1965, to create Medicare. It was called the Social Security Amendments Act of 1965.

The SSA spent the following year detailing a plan for starting the program, which officially began July 1, 1966.

More than 19 million people enrolled. Today nearly 70 million benefit from Medicare, and about 9 in 10 are 65 or older.

This story, originally published Feb. 19, 2020, was updated with additional information and a graphic.

Get Started With Medicare, Centers for Medicare & Medicaid Services
Plan for Medicare, Social Security Administration
Medicare booklet, Social Security Administration
Get Ready for Medicare package (automatically enrolled), Medicare.gov
How to drop Part A & Part B, Medicare.gov
New Medicare Card Project, Centers for Medicare & Medicaid Services
Original Medicare (Part A and B) Eligibility and Enrollment, Centers for Medicare & Medicaid Services
When to sign up for Medicare and Sign Up for Medicare, Social Security Administration
Special Enrollment Periods for Part A & Part B, Medicare.gov
Topic No. 751, Social Security and Medicare Withholding Rates, IRS
Premiums: Rules for Higher-Income Beneficiaries, Social Security Administration
Fact sheet: 2025 Medicare costs, Medicare.gov
Report on the Implementation of the 1965 Amendments, Social Security Administration
Medicare Monthly Enrollment, May 2025, Centers for Medicare & Medicaid Services
Disability, Social Security Administration
Medicare and Medicaid Employment Supports, Ticket to Work, Social Security Administration
Disability benefits approval process, Social Security Administration

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Andy Markowitz is an AARP senior writer and editor covering Social Security and retirement. He is a former editor of the Prague Post and Baltimore City Paper.

Phil Pruitt is an AARP writer and editor focusing on Social Security. He is a former editor at Scripps News and Yahoo News and was on the start-up staff at USA Today, where he held numerous editing positions.

Jammie Lyell is the Social Security program manager for AARP's office of community, state and national affairs. He formerly worked at the Social Security Administration as a legal administrative specialist and technical expert.