By Andrea Bonner
Updated May 20, 2020

Key Takeaways

  • You are automatically enrolled in Original Medicare if you have received Social Security benefits for at least four months before turning 65; or you are under 65 but eligible for Medicare because you have a disability
  • If you want to enroll or make changes to an Original Medicare, Medicare Advantage, Medicare Part D, or Medicare Supplement plan, there are several different periods you can make your elections
  • The Initial Enrollment Period (IEP) begins three months before the month you turn 65 and ends three months after your birthday month
  • If you do not sign up for Original Medicare during the IEP, you can enroll during the General Enrollment Period, which runs from January 1 to March 31 each year
  • If you want to reevaluate your coverage options and make enrollment changes, Open Enrollment starts on October 15 and ends on December 7 each year
  • If you qualify for special circumstances, you can make changes to your Medicare Part D or Medicare Advantage plans during the Special Enrollment Period

Knowing when to sign up for Medicare is important because if you miss an enrollment deadline, you could face financial penalties, expensive premiums, or experience a gap in healthcare coverage. Keep reading to find out if — and when — you have to sign up for Medicare. By signing up at the right time, you will be safeguarding your access to care — and your wallet.

Do You Have to Enroll in Medicare?

Many people who are eligible for Medicare do not actually have to sign up. This is because they will be automatically enrolled in Parts A and B (also known as Original Medicare).

How do you know if this group includes you? In most cases, it depends upon whether or not you are receiving Social Security benefits.

Who is Automatically Enrolled in Medicare?

In most cases, you will not need to sign up for Medicare Parts A and B if you:

1. Have received Social Security benefits for at least four months before you turn age 65:

  • You will be automatically enrolled in Part A and Part B starting the first day of your birthday month.
  • If your birthday is on the first day of the month, you will be automatically enrolled on the first day of the previous month (i.e. if your birthday is August 1, your coverage would begin July 1).
  • You should receive your Medicare card in the mail three months before your 65th birthday.

2. Are under 65 and are eligible for Medicare because you have a disability:

  • You will be automatically enrolled in Part A and Part B after you have received disability benefits from Social Security (or the Railroad Retirement Board) for 24 months. These don't have to be consecutive months.
  • You will receive your Medicare card in the mail three months before your 25th month of disability benefits.

It is important to note that even if you are automatically enrolled in Medicare Parts A and B, you will still have to sign up for a Medicare Advantage plan, Medicare Part D, or Medicare Supplement plan if you choose one of those plan options.

Who Must Enroll in Medicare?

If you will not have received Social Security benefits for at least four months before you turn 65, you must sign up for Medicare Parts A and B.

In order to do this, you must first enroll with Social Security in one of the following ways:

Find a Medicare plan that fits your budget

When to Enroll in Medicare and Medicare Supplement Plans

If you do have to sign up for Medicare, or you were automatically signed up and want to purchase a Medicare Supplement, Medicare Advantage, or Part D plan, there are specific periods in which you can enroll.

These periods include:

Initial Enrollment Period (IEP)

If you are new to Medicare, you can sign up for Parts A and B, Part C (a Medicare Advantage plan), Part D (a prescription drug plan), or a Medicare Supplement (Medigap) plan during your Initial Enrollment Period (IEP).

Most people who sign up for Part A during their IEP are eligible for premium-free Part A. Your IEP is seven months long and:

  • Begins three months before the month you turn 65
  • Includes your birthday month
  • Ends three months after your birthday month

Example: If you turn 65 on September 17, your IEP begins on June 1 and ends on December 31.

If you want to purchase a Medicare Advantage policy, Medicare Part D, or a Medigap plan to supplement your Original Medicare, the best time to do so is during your IEP. The reasons for this include:

  • You will typically enjoy lower prices and more choices among policies.
  • You will not be subject to underwriting, meaning that insurers cannot reject you or charge you more if you have health problems.

Medicare General Enrollment Period

If you did not sign up for Parts A and B during your Initial Enrollment Period, the next time you can sign up will be during the General Enrollment Period. This period runs from January 1 to March 31 each year.

If you sign up during this period, you will not get premium-free Part A. Instead, you will have to pay — the cost for which could be anywhere from $252-$458 per month.

Medicare Open Enrollment (Annual Enrollment)

If you already are a Medicare beneficiary, you may want to periodically reevaluate your coverage. If you decide to make changes, you can do so during the Open Enrollment Period. Open Enrollment starts on October 15 and ends on December 7 each year.

Any changes you make during Open Enrollment will take effect on January 1 of the next year. For example, a change made during the 2020 Open Enrollment Period will take effect on January 1, 2021.

The following is what you can do during the Open Enrollment Period:

  • Switch from Original Medicare to Medicare Advantage
  • Switch from Medicare Advantage back to Original Medicare
  • Change to a different Medicare Advantage plan
  • Sign up for Part D if you have not done so already (although a late enrollment fee may apply)
  • Change to a different Part D plan, if you already have one
  • Drop your Medicare Part D coverage completely

Medicare Special Enrollment

There are certain periods of time when you can make changes to your Medicare Advantage and Medicare Part D coverage due to special circumstances. These are called Special Enrollment Periods (SEPs).

There is a long list of circumstances that would make you eligible for a Special Enrollment Period, and each instance has its own rules. Listed below are three of the most common reasons people qualify for an SEP:

1. If you move to a location where your current plan is not available. In this case, you can:

  • Switch to a new Medicare Advantage plan
  • Switch to a new Medicare Part D plan.
  • Switch from Medicare Advantage to Original Medicare

If you let your plan provider know before you move, you can switch plans beginning the month before the month you move, and through the full two months after you move. For example, if you move in September, you could switch plans between August through November.

If you inform your plan provider after you move, you can switch plans beginning the month that you tell your plan provider, and for two more full months thereafter. For example, if you moved in July, but did not inform your plan provider until August, you could switch plans during the months of August through October.

2. If you have lost coverage involuntarily (from Medicaid, an employer, etc.), you can:

  • Join a Medicare Advantage plan
  • Join a Medicare Prescription Drug plan

You can sign up for two full months after the month your previous coverage ends. For example, if you left your job and your group health insurance ended in October, you could sign up through December.

3. If your plan is no longer available (Medicare has terminated its contract with your plan), you can:

  • Switch to a different Medicare Advantage Plan
  • Switch to a different Medicare Part D plan

You can sign up beginning two months before the plan's contract with Medicare ends, and ending one full month after the contract ends. For example, if your plan is terminated in May, you could sign up for a new plan beginning in March and ending in June.

Know When to Enroll in Medicare

With all of these options, one is left to wonder exactly when you should sign up for Medicare. Overall, the very best time to sign up for Original Medicare, a Medicare Advantage Plan, Medicare Part D, or a Medicare Supplement is when you first become eligible — which is during your Initial Enrollment Period. This is why you should carefully research the types of coverage that are available to you well before your Initial Enrollment Period starts.

Andrea Bonner is a healthcare writer with more than 10 years of experience covering senior health. She is from the Raleigh-Durham area in North Carolina.