Medicare Open Enrollment: What You Need To Know

Your guide to the Annual Enrollment Period, plan changes, and how to make the most of your Medicare options

Medicare Open Enrollment can mean different things depending on which enrollment period you are referring to. There are two distinct windows each year when Medicare beneficiaries can make changes to their coverage. Knowing the difference — and knowing what you can and cannot do during each — can save you money and help ensure your coverage fits your needs.

The Annual Enrollment Period (AEP) – October 15 to December 7

The Annual Enrollment Period, commonly called AEP or simply "Medicare Open Enrollment," runs from October 15 through December 7 each year. This is the primary window when most Medicare beneficiaries can review their current coverage and make changes for the coming year.

AEP lasts just 54 days, so it moves quickly. During this period you will typically see mailboxes filled with plan mailings and television ads urging you to review your options. That sense of urgency is warranted. The decisions you make during AEP affect your coverage for the entire following year.

What You Can Change During AEP

During the Annual Enrollment Period you are permitted to make the following changes:

Switch from one Medicare Advantage (MA) plan to another — If your current plan is raising premiums, dropping providers, or no longer covering your prescriptions at a level you find acceptable, you can move to a different MA plan.
Switch from one Medicare Part D drug plan to another — Stand-alone prescription drug plans can change their formularies and cost-sharing year to year. According to the American Association for Medicare Supplement Insurance, beneficiaries with a stand-alone Part D plan could save an average of $486 per year simply by comparing and switching plans.
Switch from Medicare Advantage back to Original Medicare — If you prefer the broader provider access of Original Medicare with a Medigap supplement, AEP is one window to make that transition.
Switch from Original Medicare to a Medicare Advantage plan — If you currently have Original Medicare and want to explore the bundled benefits that many MA plans offer, AEP is the time to enroll.
Add, drop, or change a Part D plan — You can add drug coverage if you do not currently have it, or drop a stand-alone plan if you are switching to an MA plan that includes drug coverage.

All changes made during AEP take effect on January 1 of the following year.

Medicare Advantage Open Enrollment Period – January 1 to March 31

The Medicare Advantage Open Enrollment Period (MA OEP) runs from January 1 through March 31 each year. This period is often confused with AEP, but it is a separate and more limited window.

MA OEP is available only to people who are already enrolled in a Medicare Advantage plan. During this period you have a one-time opportunity to:

Switch to a different Medicare Advantage plan — including one that either includes or does not include prescription drug coverage.
Drop your Medicare Advantage plan and return to Original Medicare — If you switch back, you may also join a stand-alone Part D drug plan at the same time.

MA OEP does not allow you to switch from Original Medicare into a Medicare Advantage plan, and it does not allow you to make changes to a stand-alone Part D plan if you are not enrolled in Medicare Advantage.

Changes made during MA OEP take effect on the first day of the month following your enrollment request.

When Do Changes Take Effect?

Knowing when your coverage actually changes is just as important as making the change itself. Here is a straightforward summary:

AEP changes (Oct 15 – Dec 7): All changes take effect January 1 of the following year.
MA OEP changes (Jan 1 – Mar 31): Changes take effect the first day of the month after you enroll. A change made in January is effective February 1, a change made in February is effective March 1, and so on.

It is important to keep your current coverage active and continue paying premiums until your new coverage begins. Do not cancel an existing plan before your new plan is confirmed as effective.

Tips for Reviewing Your Plan Each Year

Many Medicare beneficiaries stay in the same plan year after year without reviewing whether it still serves them well. Plans change annually — premiums go up, drug formularies shift, and provider networks can narrow. A plan that was excellent two years ago may no longer be the best fit today.

Here are practical steps to take before AEP closes each December 7:

Read your Annual Notice of Change (ANOC). Plans are required to mail this document to you in September. It outlines every change to your plan — cost-sharing, formulary, network, and benefits — taking effect January 1. If you have not received your ANOC by October 1, call your plan directly to request a copy.
Check whether your doctors are still in-network. Medicare Advantage plans use networks, and providers can leave a network mid-year or at renewal. Confirm your primary care physician and any specialists you use regularly are still covered.
Review your prescription drug costs. Run a formulary check on Medicare.gov or ask a local agent to compare what your current plan charges for your specific medications versus what competing plans would charge.
Consider your health changes from the past year. If you had surgery, were diagnosed with a chronic condition, or began seeing new specialists, your coverage needs may have shifted. A plan optimized for low premiums may not be right if you now need more frequent care.
Compare total out-of-pocket exposure, not just premiums. A plan with a lower monthly premium can end up costing more if its deductibles, copays, and out-of-pocket maximums are higher. Look at the full picture.
Do not wait until December 7. Licensed Medicare agents book up quickly as AEP draws to a close. If you want professional help comparing options, reach out early — ideally in October or early November.

How a Local Medicare Agent Can Help

Medicare plan options vary significantly by county and ZIP code. A local Medicare agent understands what plans are available in your specific area, which provider networks are strong, and which drug formularies are most favorable for common prescriptions. That local knowledge is difficult to replicate on your own.

A licensed and independent Medicare agent can:

Compare multiple Medicare Advantage and Part D plans side by side on your behalf
Run a drug cost comparison across available plans using your actual prescription list
Explain the difference between Medicare Advantage and Original Medicare with a Medigap supplement, and help you choose the right structure for your situation
Walk you through the enrollment process and confirm that your application was received and processed correctly
Be available after enrollment for questions and service throughout the year

Independent agents are typically compensated by the insurance carriers, not by you directly, so their advice costs you nothing out of pocket. Working with someone who represents multiple carriers — rather than a single company — gives you access to a broader range of options.

Find a Local Medicare Agent →