Medicare Enrollment Periods: Don't Miss These Deadlines

Medicare doesn't let you sign up whenever you feel like it. There are specific windows — enrollment periods — during which you can join, switch, or drop coverage. Missing the right window can mean waiting months for coverage to start, or paying a permanent penalty for years to come.

Here's a clear breakdown of every enrollment period you need to know.

Initial Enrollment Period (IEP): Your First Chance

The Initial Enrollment Period is the window you get when you first become eligible for Medicare — typically when you turn 65. It lasts 7 months:

• 3 months before your birthday month
• Your birthday month
• 3 months after your birthday month

During this window, you can sign up for:

• Medicare Part A (hospital)
• Medicare Part B (medical)
• A Medicare Advantage plan (Part C)
• A Part D prescription drug plan
• A Medigap (Medicare Supplement) policy (during IEP, Medigap Open Enrollment also begins)

When coverage starts depends on when you enroll. Signing up in the three months before your birthday month means coverage starts the first of your birthday month. Enrolling later in the IEP delays the start of coverage.

If you miss your IEP without qualifying for a Special Enrollment Period, you'll have to wait for the General Enrollment Period (January 1 – March 31) to sign up for Parts A and B, with coverage not starting until July 1. And you may owe a late penalty.

Annual Enrollment Period (AEP): Your Yearly Review Window

Dates: October 15 – December 7 each year Coverage start: January 1 of the following year

The AEP is Medicare's annual open enrollment — the time when everyone with Medicare can make changes to their coverage. During AEP, you can:

• Switch from Original Medicare to Medicare Advantage
• Switch from Medicare Advantage back to Original Medicare
• Switch from one Medicare Advantage plan to another
• Join, switch, or drop a Part D prescription drug plan

This is the most important enrollment period for existing Medicare beneficiaries. Every fall, you should review your current plan against available alternatives — because plans change their premiums, formularies, and networks each year.

If you don't make any changes during AEP, your current coverage automatically continues into the next year (with whatever changes the plan has made to its terms).

Note on Medigap: Medigap plans are NOT purchased or changed during AEP. Medigap has its own rules — see below.

Medicare Advantage Open Enrollment Period (OEP): A Mid-Year Second Chance

Dates: January 1 – March 31 each year Coverage start: First of the month following your enrollment

The OEP is specifically for people already enrolled in a Medicare Advantage plan. During this period, you can:

• Switch to a different Medicare Advantage plan
• Drop Medicare Advantage and return to Original Medicare (and add a Part D plan)

You cannot use OEP to switch from Original Medicare to Medicare Advantage, or to join a Part D plan if you're already on Original Medicare. It's strictly for people already in a Medicare Advantage plan.

OEP is useful if you enrolled in an Advantage plan during AEP and then discovered — during January or February — that your doctors aren't in-network, your prescriptions aren't covered as expected, or you're simply not happy with the plan.

Special Enrollment Periods (SEPs): When Life Changes Your Coverage Needs

SEPs allow you to make Medicare changes outside the standard enrollment windows when certain qualifying life events occur. Common SEP triggers include:

Losing employer coverage: If you were delaying Medicare because you had active employer health coverage, you get an 8-month SEP starting the month after employment or coverage ends — whichever comes first. This is one of the most important SEPs and must be used carefully.

Moving: If you move outside your current plan's service area, or move to a new area where different plans are available, you may qualify for an SEP to change plans.

Plan losing its Medicare contract: If your Medicare Advantage or Part D plan is no longer available in your area, you get an SEP to choose a new plan.

Losing Medicaid or Extra Help: If you had Medicaid or the Part D Low-Income Subsidy and lose eligibility, you have an SEP to make changes.

Gaining Medicaid or Extra Help: You get a continuous SEP — you can change your Part D plan once per quarter — if you have both Medicare and Medicaid or receive Extra Help.

Other qualifying events: Moving into or out of a nursing facility, your plan receives certain quality ratings, or other specific circumstances.

SEPs have specific timeframes — usually 2 months from the qualifying event. Don't assume you have unlimited time once a triggering event occurs.

Medigap Open Enrollment: A One-Time Protected Window

Medigap (Medicare Supplement) insurance has its own special enrollment period that's separate from all the above. Your Medigap Open Enrollment Period starts the month you're both 65 or older AND enrolled in Part B — and lasts 6 months.

During this 6-month window, insurers cannot deny you a Medigap policy or charge you more due to pre-existing health conditions. This is called "guaranteed issue" protection.

After this window closes, insurers in most states can use medical underwriting — meaning they can deny you coverage or charge higher premiums based on your health history. This is a one-time window that doesn't come around again, so understanding its value is important.

Quick Reference Calendar

Medicare enrollment is one of those areas where timing genuinely matters. Getting the windows right protects your coverage, your wallet, and your peace of mind.

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Have questions? Call 1-877-443-3251 for free, no-obligation help from a licensed agent.

This is an educational website and is not affiliated with or endorsed by Medicare or any government agency. We connect consumers with licensed insurance agents who can help with Medicare enrollment. Not all plans or options are available in all areas. Please contact Medicare.gov, 1-800-MEDICARE, or your local State Health Insurance Program (SHIP) to get information on all of your options.