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Unpacking Medicare: What you need to know about Medicare enrollment periods (and when you can change your plan)

Christina Joseph By Christina Joseph

 You mark every important date in your life on the calendar: a grandchild’s birthday, your wedding anniversary, summer vacation, even doctor appointments. But there are other critical moments you’ll want to make sure to remember, too — like when you can sign up for a Medicare plan.

The timeframe for enrolling in a Medicare plan is called an enrollment period.

You have a seven-month window around the month you turn 65 to first sign up for a Medicare plan.

If you miss the right time to enroll, your coverage may be delayed, or you could face penalties later on. And that may end up costing you more.

Here are the key enrollment periods you need to know:

1.     Initial Enrollment Period

Congratulations, you’re turning 65! Now you can enroll in a Medicare plan. You have a seven-month window to join during this period — from three months before the month you turn 65, through your birthday month and to three months after the month you turn 65. During this time, you can:

  • Enroll in Medicare (Parts A and B) – contact Social Security to learn more
  • Enroll in a stand-alone Medicare prescription drug plan (Part D)
  • Enroll in a Medicare Advantage plan (Part C)

If you don’t sign up for Medicare Parts A and B or Part D when you’re first eligible, you could face penalties in the form of higher premiums. Read more about avoiding penalties.

You may be eligible to get Medicare earlier if you have a disability, end-stage renal disease (ESRD) or ALS (also called Lou Gehrig’s disease).

Check out our chart on coverage start dates when you enroll for the first time.

Tip: If you’re already receiving Social Security when you turn 65, you will be automatically enrolled in Original Medicare (Parts A and B).

Find more information on the different parts of Medicare here.

2.     Medicare Supplement Open Enrollment Period

If you’re looking to supplement your Original Medicare coverage to help with additional costs, the best time to buy a Medicare Supplement plan is during the six-month enrollment period that starts the first day of the month you turn 65 — as long as you have signed up for Medicare Part B.

If you don’t sign up for a Medicare Supplement plan during this Open Enrollment Period, you may not be able to buy a Medicare Supplement plan.  Unless you have a guaranteed issue right, you may be required to answer medical questions.

You can find information here on Medicare Supplement plans and how they may help you cover the gaps in Original Medicare.

3.     General Enrollment Period

You can also sign up for Part A and/or Part B between January 1 and March 31 each year if both of these conditions apply:

  • You didn't sign up when you were first eligible.
  • You aren’t eligible for a Special Enrollment Period (see below).

Your coverage will start July 1. And you may be subject to penalties.

4.     Annual Enrollment Period 

Anyone can make changes to their coverage and enroll in a Medicare plan each year, from October 15 to December 7.

  • If you have Original Medicare, you can switch to a Medicare Advantage plan — or vice versa.
  • You can switch from a Medicare Advantage plan with drug coverage to one without — or vice versa.
  • You can join or drop a Medicare prescription drug plan.
  • You can also update your coverage by switching to a new plan from your current insurer or switching to a new insurer.

If you choose to make a change during the Annual Enrollment Period, your new coverage won’t begin until January 1.

For more detail on your coverage options, check out the coverage comparison chart here.

Tip:  If you’re happy with your current coverage, you’re not required to make a change. In most cases, your current Medicare plan will automatically renew on January 1.

5.     Medicare Advantage Open Enrollment Period

This period takes place from January 1 through March 31 annually. It allows individuals enrolled in a Medicare Advantage plan to make a one-time election to go to either another Medicare Advantage plan with or without prescription drug coverage or Original Medicare. You’ll also be able to enroll in a Medicare prescription drug plan.

In either case, your new coverage will start on the first day of the month following the month you make a change.

Tip: If you go back to Original Medicare, you can also add a Medicare Supplement plan. However, unless you’re still within the six-month Medicare Supplement Enrollment Period, the insurance companies will require you to answer medical questions to qualify for coverage.

Medicare Advantage plans are only available through private insurers like Aetna®. Medicare Advantage plans may also include prescription drug coverage. Learn more about Medicare Advantage here.

6.     Special Enrollment Period

During a Special Enrollment Period (SEP), you can join, switch or drop a Medicare Advantage or prescription drug plan outside the basic enrollment periods. In order to qualify for an SEP, certain events must occur that require you to change your coverage. Common scenarios include:

  • You move out of your plan’s service area.
  • You move back to the U.S. after living abroad.
  • You move into or out of a skilled nursing facility, psychiatric facility, rehab hospital or long-term care facility.
  • Your employment or your employer-provided plan ends.

Rules vary on what changes you can make and when you can make them. Refer to for more details.

Find out what happens after you enroll in an Aetna Medicare Advantage plan.

About the author

Christina Joseph Robinson is a veteran editor and writer from New Jersey who still loves to read the old-fashioned newspaper. She’s raising two fruit-and-veggie loving daughters to balance all the treats Grandma sends their way. Christina’s health goal is to resume her workout routine after being sidelined by injuries.