Medicare Annual Enrollment Period: What You Can Actually Change (Oct 15–Dec 7)

Every fall, from October 15 through December 7, Medicare runs its Annual Enrollment Period (AEP). TV ads remind you it is "time to compare your Medicare options." Insurance agents call. Mailers arrive daily.

Most of it is noise. Here is what the Annual Enrollment Period actually allows you to do, what it does not, and how to decide if you should make any changes.

What You Can Change During AEP

Any changes you make during AEP take effect January 1 of the following year.

What You Cannot Change During AEP

The Annual Enrollment Period does not let you add Medigap (Medicare Supplement) coverage without medical underwriting. Medigap Open Enrollment — the period when companies must accept you at standard rates regardless of health — is tied to when you first enroll in Part B, not to the annual enrollment window. Outside of your initial Open Enrollment Period, Medigap companies in most states can charge you more based on health history or deny coverage entirely.

If you want to switch from Medicare Advantage to Medigap, you can return to Original Medicare during AEP — but getting a Medigap policy may require going through underwriting. Some states have more consumer-friendly Medigap rules, so check your state's specific rules.

Should You Actually Change Anything?

The case for reviewing your coverage every year during AEP is real. Plans change their premiums, formularies, and networks annually. A plan that was excellent this year may have dropped your doctor, stopped covering one of your key medications, or significantly increased its premium. Reviewing once a year takes an hour and can save hundreds of dollars.

The case against changing just because you can: disrupting a plan that works for you, especially a Medicare Advantage plan with good care coordination and a network that includes all your doctors, has real costs — new referrals, new preauthorizations, re-establishing care. Do not switch just because a new plan advertises lower premiums without checking the full picture.

How to Review Your Plan in AEP

  1. Get your current plan's Annual Notice of Change (ANOC) — mailed to you in September each year. It shows what is changing in your current plan for the coming year.
  2. Check whether your doctors are still in-network for the coming year.
  3. Run your current medications through the plan's formulary for the coming year — drug coverage can change.
  4. Compare your current plan's total costs (premium + expected out-of-pocket) against alternatives on medicare.gov/plan-compare.
  5. If you find something meaningfully better, make the switch. If not, stay where you are.

The January 1 OEP: Another Window

If you made a change during AEP and regret it, or if you want to revisit, there is also a Medicare Advantage Open Enrollment Period from January 1 through March 31. During this window, you can switch from one Medicare Advantage plan to another, or drop Medicare Advantage and return to Original Medicare (with or without a Part D plan). You can only use this window once.

The most important thing to do during AEP is not find a new plan — it is confirm that your current plan still works for you. Start with your Annual Notice of Change and your doctor list, and only look for alternatives if you find a problem. Switching plans unnecessarily creates administrative hassle and potential care disruption for minimal gain.

Reminder: Ready at 65 is not affiliated with Medicare, CMS, the SSA, or any government agency. This article is general educational information, not financial, legal, medical, or insurance advice. Rules, costs, and deadlines change — verify current details at Medicare.gov or by calling 1-800-MEDICARE before making any decision. Full disclaimer →

Don't Make a Medicare Decision Without the Checklist

The step-by-step enrollment checklist from inside the book — dates, forms, phone numbers. Free, one email, no insurance pitch.

Get the Free Enrollment Checklist