How and When to Enroll or Switch Medicare Advantage or Medicare Supplement Insurance Plans

Overview

You’ve had your Medicare coverage for a while, but your healthcare needs have changed. Maybe your doctor is no longer in your network, or you’ve realized you need lower out-of-pocket costs. Can you switch now—or do you have to wait?

Many people are surprised to learn that you can’t enroll in a Medicare Advantage or Medicare Supplement Insurance plan anytime. Each type of plan follows specific enrollment windows and switching rules. Missing those windows could delay coverage or cost you more.

This guide breaks down how and when to enroll or switch Medicare Advantage or Medicare Supplement Insurance plans, so you can make confident coverage decisions.

Can You Enroll in a Medicare Advantage or Medicare Supplement Insurance Plan Anytime?

In most cases, you can only enroll in a Medicare Advantage or Medicare Supplement Insurance plan during specific enrollment periods. The tables below show how the timelines and rules differ between the two types of plans.

Here’s how they work:

Enrolling in a Medicare Advantage Plan

Note: You can only be enrolled in one Medicare Advantage plan at a time. Switching between plans or returning to Original Medicare must occur during these designated periods unless you qualify for a Special Enrollment Period.

How to Enroll in a Medicare Advantage Plan

Enrolling in a Medicare Advantage plan involves a few clear steps:

1. Confirm eligibility.
   You must have Medicare Part A and Part B and live in the plan’s service area.

2. Compare plan options.
   Use MedicareGuide’s parent company, Healthcare.com, or browse the best Medicare Advantage companies for 2026 to see which insurers offer top-rated coverage in your area.

3. Check coverage details.
   Review doctor networks, prescription formularies, out-of-pocket maximums, and extra benefits like dental or vision.

4. Enroll during an eligible period.
   You can apply online at Medicare.gov, directly through the insurer, or via a licensed Medicare agent.

How to Enroll in a Medicare Supplement Insurance Plan

Unlike Medicare Advantage, Medicare Supplement Insurance plans (also called Medigap) work alongside Original Medicare to cover costs like deductibles and coinsurance.

Your best opportunity to enroll is during your Medigap Open Enrollment Period, which lasts for six months starting the month you’re 65 or older and enrolled in Part B.

During this window:

• You can buy any Medicare Supplement Insurance plan available in your state. Our Medicare by State guide shows which Medicare Supplement Insurance plans are available where you live and how rules differ across the U.S.

• You have guaranteed issue rights, meaning insurers can’t deny you coverage or charge more due to preexisting conditions.

After this window ends, you can still apply for a Medicare Supplement Insurance plan, but insurers can require medical underwriting—they can deny your application or charge higher premiums based on your health history.

Before enrolling, review the best Medicare Supplement Insurance companies for 2026 to compare coverage, premiums, and customer satisfaction ratings.

Outside these windows, you can only join a Medicare Advantage or Medicare Supplement Insurance plan if you qualify for a Special Enrollment Period (SEP)—for example, if you move out of your plan’s area or lose existing coverage.

If you’re unsure which enrollment window applies to you, check out our 2026 Guide to Medicare Plans for a full breakdown of timelines and eligibility rules.

When Can You Switch Medicare Advantage or Medicare Supplement Insurance Plans?

Switching Medicare Advantage or Medicare Supplement Insurance plans depends on what type of plan you have now.

Switching Medicare Advantage Plans

You can change your Medicare Advantage plan:

• During the Annual Enrollment Period (Oct 15 – Dec 7).
  Your new coverage starts Jan 1.

• During the Medicare Advantage Open Enrollment Period (Jan 1 – Mar 31).
  You can switch to another Medicare Advantage plan or go back to Original Medicare.

If you’re thinking about making the switch, check our in-depth guide on switching from Medicare Advantage to Original Medicare to understand what happens to your coverage and when it’s allowed.

If you move or experience a major life change (like losing employer coverage), you might qualify for a Special Enrollment Period to change plans at any time.

Switching from Medicare Advantage to Medicare Supplement Insurance

You can drop your Medicare Advantage plan and return to Original Medicare during the same enrollment periods above. However, you might not always be able to buy a Medicare Supplement Insurance plan immediately—unless you qualify for guaranteed issue rights (for example, if your Medicare Advantage plan ends coverage in your area).

How to Switch Medicare Supplement Insurance Plans

You can technically apply to switch Medicare Supplement Insurance plans any time of year, but there’s an important catch:

• Outside your Medigap Open Enrollment Period, insurance companies can require medical underwriting and may deny coverage or charge more.

  Scenario	Can You Switch Anytime?	Underwriting Required?
  Within first 6 months of Part B enrollment	✅ Yes	❌ No
  After open enrollment	✅ Yes	✅ Usually yes
  Guaranteed issue event (e.g., Medicare Advantage plan ends, move out of service area)	✅ Yes	❌ No

Tips for switching Medicare Supplement Insurance plans:

• Don’t cancel your current policy until the new one is approved.

• Compare premiums and coverage benefits before switching.

• Consider potential waiting periods for preexisting conditions.

Tips for a Smooth Transition

Switching your Medicare Advantage or Medicare Supplement Insurance plan doesn’t have to be stressful. Keep these best practices in mind:

• Review your annual “Medicare & You” handbook for up-to-date coverage details.

• Check provider networks before switching to a new plan to ensure your doctors are covered.

• Coordinate prescription coverage (Part D) if you’re leaving a Medicare Advantage plan that includes drug benefits.

• Avoid coverage gaps by aligning your effective dates when switching.

• Compare total costs, not just premiums—consider copays, coinsurance, and out-of-pocket maximums.

For a broader look at plan types, benefits, and timelines, read our 2026 Guide to Medicare Plans, which covers everything from Medicare Advantage options to Medicare Supplement Insurance policies and drug coverage.

Bottom Line

Understanding when and how to enroll—or switch—your Medicare Advantage or Medicare Supplement Insurance plan can save you time, money, and frustration. Whether you’re joining a Medicare Advantage plan for extra benefits or a Medicare Supplement Insurance plan for cost protection, the key is knowing your enrollment windows and acting during the right time.