On Medicare? 4 Important Dates to Mark on Your Calendar

Your health insurance plan is a huge difference-maker in how much you spend annually. The right plan covers the providers, treatments, and prescription drugs you need at the lowest possible cost, while the wrong plan could leave you paying full price for services you can't afford.

It's important for everyone to review their health insurance coverage carefully each year, but this is especially important for seniors living on a fixed income. The Medicare open enrollment period is often your only chance to switch plans for the coming year.

Here are the important dates you need to mark on your calendar so you don't miss the opportunity to find your best health insurance for 2026.

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1. Oct. 15, 2025

Oct. 15, 2025, is the start of Medicare's annual open enrollment period. This is the window when everyone on Original Medicare can review their existing plans and change their coverage for 2026.

You should have already received notices from Medicare and any Part D or Medigap plan providers you work with, detailing what's changing with their plans next year. Review this carefully and note any gaps in the coverage you want filled. This is particularly important if you've experienced health changes recently or if you've started new prescription medications.

You can compare plan options in your area on Medicare's website. You can choose from Part D plans for prescription drugs, as well as Medigap and Medicare Advantage plans. Medigap plans are separate health insurance plans available through private insurers. These are intended to fill some of the holes in Original Medicare. They have their own premiums, copays, and deductibles.

Medicare Advantage plans are alternatives to Original Medicare. Private insurers offer these plans, which cover everything in Original Medicare, as well as some extras. If you opt for one of these, you'll only have a single premium, copay, and deductible.

2. Dec. 7, 2025

The 2025 Medicare open enrollment period ends on Dec. 7, 2025. You must choose a new plan by then if you want your coverage to begin on Jan. 1, 2026.

If you miss this window, you will remain on your existing Medicare plan(s) in 2026. You likely won't be able to change coverage until the next open enrollment period begins in October 2026.

There is an exception if you qualify for a special enrollment period, though. This might be the case if you move or if you lose existing health insurance, like if you quit your job and are no longer on your employer's plan.

3. Jan. 1, 2026

If you change your Medicare coverage during the open enrollment period, your new coverage will begin on Jan. 1, 2026. This is also when any benefit or cost changes will take effect if you choose to remain on your existing plan.

Jan. 1, 2026, also marks the beginning of the period when those already on Medicare Advantage plans can switch their coverage. You can switch to a different Medicare Advantage plan or back to Original Medicare during this time. If you switch to Original Medicare, you'll also have the chance to enroll in a Part D plan.

If you change your Medicare Advantage plan during this window, coverage will begin on the first of the month after you elect the change. For example, if you choose a new plan on Jan. 15, 2026, the change will take effect on Feb. 1, 2026.

4. March 31, 2026

This is your last opportunity to change your Medicare Advantage plan coverage for 2026. If you make a change on this day, your new plan will go into effect on April 1, 2026.

If you have questions about your existing Medicare coverage or any of the other plans you're considering, you can always call 1-800-MEDICARE for help comparing options. It's best to start as soon as possible so you have plenty of time to find the plan that will keep your retirement healthcare expenses manageable for next year.

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