Medicare’s Annual Enrollment Period runs from October 15 through December 7 every year. During this window, current Medicare beneficiaries can switch between Original Medicare and Medicare Advantage, add or drop Part D prescription drug coverage, or change their existing Medicare Advantage or Part D plan. Any changes made during this period take effect January 1 of the following year. This is the primary opportunity for most beneficiaries to adjust their coverage to match changing health needs and prescription requirements.

Understanding Medicare Open Enrollment

Medicare Open Enrollment, officially called the Annual Enrollment Period (AEP), is a federally mandated window that allows current Medicare beneficiaries to review and modify their coverage. According to the Centers for Medicare & Medicaid Services, this period occurs at the same time each year, from October 15 through December 7 (Medicare.gov, 2026). Unlike the Initial Enrollment Period (when someone first becomes eligible for Medicare at age 65), the Annual Enrollment Period applies to people already enrolled in Medicare who want to make changes.

The period exists because Medicare is not a one-size-fits-all program. Beneficiaries’ health needs, prescription drug requirements, preferred doctors, and financial situations change over time. Open enrollment gives everyone a guaranteed opportunity to reassess and adjust their coverage without medical underwriting or penalties.

Who Can Make Changes During This Period

Any current Medicare beneficiary can use the Annual Enrollment Period to make coverage changes, regardless of their current plan type or health status. This includes:

  • People enrolled in Original Medicare (Parts A and B) who want to add prescription drug coverage (Part D) or switch to a Medicare Advantage plan
  • Medicare Advantage enrollees who want to return to Original Medicare or switch to a different Medicare Advantage plan
  • Part D prescription drug plan enrollees who want to change to a different standalone Part D plan
  • Dual-eligible beneficiaries (those with both Medicare and Medicaid)

Importantly, you do not need to have a qualifying life event (such as moving or losing other coverage) to make changes during this period. The window is open to everyone with Medicare, and health status or pre-existing conditions cannot be used to deny enrollment or charge higher premiums.

What Coverage Changes You Can Make

The Annual Enrollment Period allows several specific changes to Medicare coverage:

Switch between Original Medicare and Medicare Advantage. You can move from Original Medicare (Parts A and B) to a Medicare Advantage plan (Part C), which bundles hospital and medical coverage and often includes prescription drug coverage. Conversely, you can disenroll from a Medicare Advantage plan and return to Original Medicare.

Add, drop, or change Part D prescription drug coverage. If you have Original Medicare, you can enroll in a standalone Part D plan, switch from one Part D plan to another, or drop Part D coverage entirely (though dropping coverage without other creditable prescription coverage can result in late enrollment penalties if you rejoin later). If you have a Medicare Advantage plan with drug coverage, you cannot add a standalone Part D plan.

Change Medicare Advantage plans. You can switch from one Medicare Advantage plan to another offered in your county. Plans vary in network, covered drugs, premiums, deductibles, and extra benefits like dental or vision coverage, so comparing options annually is important as plan details change each year.

Add or drop extra benefits. Some Medicare Advantage plans include additional coverage for dental, vision, hearing, fitness memberships, or over-the-counter allowances. You can select a plan with these benefits or move to one without them if they are not needed.

As discussed in foundational public health resources such as the NCBI Bookshelf’s health and medicine library, understanding coverage options and enrollment periods is essential for managing healthcare access and costs effectively.

Important Deadlines and Timeline

The enrollment window runs exactly 54 days, from October 15 through December 7. Any enrollment or plan change submitted by 11:59 PM on December 7 will take effect on January 1 of the following year. Missing this deadline means you generally cannot make changes until the next Annual Enrollment Period, unless you qualify for a Special Enrollment Period due to specific life events (such as moving out of your plan’s service area or losing employer coverage).

Plan materials for the upcoming year, including the Annual Notice of Change (ANOC) and Evidence of Coverage (EOC), are mailed to current enrollees in late September. These documents detail any changes to premiums, deductibles, covered drugs, and provider networks for the next year. Reviewing these materials before the enrollment period opens allows you to compare your current plan against alternatives and make an informed decision.

Read also: Medicare Open Enrollment 2026: Key Decisions to Make Before December 7 in the US

What You Cannot Change During Open Enrollment

While the Annual Enrollment Period is broad, it does not allow every possible change. You cannot use this period to enroll in Medicare for the first time (that requires the Initial Enrollment Period or a Special Enrollment Period). You also cannot drop Medicare Part A or Part B during this window. Part A (hospital insurance) is premium-free for most people, and dropping Part B (medical insurance) is only possible during specific times and has consequences if you want to re-enroll later.

Additionally, you cannot enroll in a Medicare Supplement (Medigap) policy during the Annual Enrollment Period with guaranteed issue rights unless you meet specific conditions. Medigap policies have their own enrollment rules, and open enrollment for Medigap occurs only during the six-month period starting when you first enroll in Medicare Part B at age 65 or older.

Why This Period Matters

Medicare Advantage and Part D plans change their coverage, costs, and networks every year. A plan that worked well last year may no longer cover your prescriptions, include your preferred doctors, or offer the same premium. According to CMS, plans can modify their formularies (lists of covered drugs), adjust copayments, change provider networks, and alter premiums annually (CMS.gov, 2026).

Reviewing your coverage every year, even if you are satisfied with your current plan, ensures you are not paying for benefits you do not use or missing out on better options. For example, if your prescription needs have changed, a different Part D plan may offer better coverage at a lower cost. If you have developed a new chronic condition, a Medicare Advantage plan with a different network or lower specialist copays may be more appropriate.

Common Mistakes to Avoid

One frequent error is assuming your current plan remains unchanged. Always review the Annual Notice of Change mailed in September rather than automatically re-enrolling. Another mistake is focusing only on the monthly premium. A plan with a low premium but high deductibles, copays, or out-of-pocket maximums may cost more overall, especially if you use healthcare frequently or take multiple prescriptions.

Some beneficiaries also wait until the last few days of the enrollment period to make changes. While the December 7 deadline is firm, submitting changes earlier in the period reduces the risk of technical issues, allows more time to compare plans, and ensures you receive confirmation before the deadline.

Finally, do not drop your current coverage before your new coverage is confirmed to start. Coverage changes take effect January 1, so if you disenroll from a plan before that date without another plan in place, you may have a gap in coverage.

How to Review and Compare Coverage

Medicare’s online Plan Finder tool at Medicare.gov allows you to enter your prescriptions, preferred pharmacies, and doctors to compare all available plans in your area. The tool estimates your total annual costs (premiums plus out-of-pocket expenses) for each plan based on your specific situation. You can also call 1-800-MEDICARE (1-800-633-4227) to speak with a representative who can help compare options.

State Health Insurance Assistance Programs (SHIPs) offer free, unbiased counseling to Medicare beneficiaries. SHIP counselors can review your current coverage, explain plan differences, and help you enroll in a new plan. Contact information for your state’s SHIP is available at Medicare.gov or by calling 1-800-MEDICARE.

Taking Action Before December 7

If you are satisfied with your current plan and have confirmed that your doctors, prescriptions, and coverage will remain the same for the next year, you do not need to take action. Your plan will automatically renew. However, if you want to make a change, you can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or by contacting the plan directly. Some plans also allow enrollment through licensed insurance agents.

Keep a record of your enrollment confirmation, including the plan name, confirmation number, and effective date. If you do not receive confirmation within a few weeks, follow up with the plan or Medicare to verify your enrollment was processed.

This article provides general educational information about Medicare open enrollment and is not personalized insurance, financial, or legal advice. Medicare rules, plan availability, and coverage details vary by location and individual circumstances. For guidance specific to your situation, consult a licensed insurance agent, your State Health Insurance Assistance Program (SHIP), or call 1-800-MEDICARE. Coverage decisions should be based on your current health needs, prescription requirements, preferred providers, and financial situation. Always verify plan details and confirm enrollment before the December 7 deadline.