Americans age 65 and older are only automatically enrolled in Medicare if they began receiving Social Security or Railroad Retirement Board (RRB) benefits at least 4 months before their 65th birthday. Enrollment is also automatic for those who qualify for Medicare due to a disability or illness. Everyone else must choose to sign up for Medicare.

When are you automatically enrolled in Medicare?

There are only three scenarios in which you are automatically enrolled in Medicare:

• You are age 65 or older AND began receiving Railroad Retirement Board or Social Security retirement benefits at least 4 months before turning 65
• You are under age 65 and have received Social Security disability benefits for 24 months (or certain disability benefits from the RRB)
• You are under age 65 and have amyotrophic lateral sclerosis (ALS), more commonly known as Lou Gehrig's disease

If any of the above scenarios apply to you, Medicare enrollment occurs automatically.

What happens when you're automatically enrolled in Medicare?

Most Medicare beneficiaries who are automatically enrolled get their Part A and Part B benefits starting the first day they're eligible. This is the:

• First day of the month you turn 65 if you age into the Medicare program (if your birthday falls on the first, your benefits begin the first of the month BEFORE your birth month)
• First day of your 25th month of collecting disability benefits
• Month your disability benefits begin if you have ALS

You will receive your red, white, and blue Medicare card in the mail 3 months before your Medicare eligibility month. For those who age into the program, this is 3 months before your 65th birthday. If you qualify due to a disability, your card should arrive during month 22 of your benefits.

The timeline is slightly different for those who are eligible due to ALS, since there isn't the same waiting period as those who qualify due to a disability. If you have Lou Gehrig's disease, you will receive your Medicare card the same month that your disability benefits begin.

What's included with Medicare auto enrollment?

Medicare auto enrollment includes Part A, hospital insurance, and Part B, medical insurance. Together, this is known as Original Medicare.

Medicare Part A helps pay for inpatient care received in a hospital or skilled nursing facility (SNF). Medicare Part B covers outpatient services like doctor visits, mental health care, durable medical equipment (DME), lab work, and more. Find the full list on Medicare.gov.

There are two other "parts" to Medicare:

• Medicare Part C is more commonly known as Medicare Advantage. These health plans are provided by private insurance companies working within the guidelines set by the Centers for Medicare & Medicaid Services (CMS). Medicare Advantage plans combine your Parts A and B benefits into a single plan that is similar to the group health insurance plans many of us had through an employer. Most Advantage plans – around 90 percent – also provide additional benefits, like prescription drug coverage.
• Medicare Part D helps pay for prescription medications. Also provided by private insurers who contract with CMS, you may join either a standalone Medicare prescription drug plan (PDP) or a Medicare Advantage Prescription Drug plan (MA-PD).

Even if you're automatically enrolled in Medicare, you have to choose whether to join a Part C or Part D plan. The best time to do this is during your Initial Enrollment Period (IEP), which we discuss in depth below.

Who must choose to sign up for Medicare?

You must choose to sign up for Medicare if you:

• Did not begin collecting Social Security or RRB retirement benefits at least 4 months before turning 65
• Qualify for Medicare due to end-stage renal disease (ESRD)

In both of these scenarios, signing up for Medicare is a choice. Enrollment is through the Social Security Administration.

The best way to sign up for Medicare is by completing the online application here. It takes less than 10 minutes to complete the online form, which is available 24 hours a day, 7 days a week.

You may also call Social Security at 1-800-772-1213 or TTY 1-800-325-0778. Representatives are available during regular business hours Monday through Friday.

Please note that local Social Security offices have not been available for in-person services since March of 2020 due to the COVID-19 pandemic. However, you may search for your local SSA office here. Always call first to both see that the local office is open and to schedule an appointment.

What happens if you live in Puerto Rico?

People who live in Puerto Rico must always choose to sign up for Medicare Part B (Part A enrollment occurs automatically). The best time is during your Initial Enrollment Period (see the next section). To sign up for Part B, please call Social Security at the toll-free number listed above.

Does everyone get an Initial Enrollment Period?

Yes, every Medicare beneficiary has an Initial Enrollment Period, even those who are automatically enrolled and those who qualify before turning 65. However, if you're automatically enrolled, all you need to do during you Initial Enrollment Period is choose a Part D plan (and Part C, if you decide you want an Advantage plan instead of Original Medicare).

Those who are not automatically enrolled must sign up for Parts A and B during their IEP. They may then join a Part C and/or Part D plan.

The Initial Enrollment Period lasts for 7 months. When it begins and ends depends on how you qualify for Medicare and when your birthday lands.

• Age into the program, born between the 2nd and last days of the month: Your IEP begins 3 months before your birth month and ends 3 months after your birth month. So, a June 4 birthday gives you an IEP lasting from March 1 through September 30.
• Age into the program, born on the 1st: Your IEP begins 4 months before your birth month and ends 2 months after it. So, if your birthday is June 1, your IEP begins February 1 and ends on August 31.
• Qualify due to a disability: Your IEP begins during your 22nd month of collecting SSDI and ends in month 28. So, if your 25th month of collecting disability benefits is in June, your IEP goes from March 1 through September 30.

Finally, if you qualify for Medicare due to ALS or ESRD, your IEP starts the same month that your Medicare benefits begin and ends 7 months later.

When else can you sign up for Medicare?

Medicare provides a variety of enrollment periods and chances to change your Medicare coverage.

• Annual Enrollment Period (AEP): From October 15 through December 7, all Medicare beneficiaries may make any changes they wish to their current plan or coverage. This includes joining or leaving a Medicare Advantage or Part D plan. Coverage choices take effect on January 1.
• General Enrollment Period (GEP): From January 1 through March 31, you may sign up for Medicare Part A and/or Part B if you are not already enrolled. Then, from April 1 through June 30, you may join a Part D or Part C plan (or both). Your coverage choices will begin on July 1.
• Medicare Advantage Open Enrollment Period (OEP): Current Medicare Advantage enrollees have from January 1 through March 31 to either switch to a new Advantage plan or return to Original Medicare. If making that changes results in you losing your prescription drug coverage, you may also join a standalone Part D plan during this time.
• Special Enrollment Period (SEP): A variety of special circumstances may qualify you for a Special Enrollment Period. Typically, these come down to losing your current coverage due to retiring, changing jobs, moving, etc. There are many ways to qualify for an SEP. Find the full list here.

Please note that failure to maintain creditable coverage may result in you owing a late enrollment penalty for Part B or Part D (and in rare cases, Part A). Learn how to avoid this fee with our article, Medicare Part B Penalty Exceptions.

What about Medigap?

Medicare Supplement Insurance, more commonly known as Medigap, helps pay your out-of-pocket Medicare costs. Coverage varies depending on which Medigap plan you choose, but all of them cover at least a portion of:

• Medicare Part A coinsurance
• Medicare Part B coinsurance or copayments
• Hospice care coinsurance or copays
• First 3 pints of blood

You also get an additional 365 lifetime reserve days for inpatient hospital care (Part A only gives you 60 lifetime reserve days). Please note that no Medigap plan pays your Part B premium.

The best time to sign up for Medicare Supplement Insurance is during your Medigap Open Enrollment Period. This 6-month period begins the day you're both enrolled in Original Medicare AND age 65 or older. During your Medigap OEP, you cannot be denied a plan nor charged a higher rate, even if you have preexisting medical conditions.