How to Sign Up for Medicare Advantage During Open Enrollment

How Medicare Advantage enrollment works

Medicare Advantage is a way to get your Medicare coverage through a private insurance company instead of Original Medicare. To sign up, you must be enrolled in Medicare Part A and Part B first, and you can only join during specific windows: the Annual Enrollment Period (October 15 to December 7 each year), when you first turn 65, or if you may have access to for a Special Enrollment Period due to a life event like moving or losing other coverage.

The process itself is straightforward — you choose a plan, contact the insurance company or Medicare directly, and submit your enrollment. Most people complete it in under an hour. The key is knowing which window applies to you and having the right information ready before you start.

Key Takeaways

You must already have Medicare Part A and Part B to join a Medicare Advantage plan, and enrollment happens only during the Annual Enrollment Period (October 15 to December 7) or a Special Enrollment Period.
You will need your Medicare card, Social Security number, and information about any current coverage when you enroll.
You can enroll through Medicare.gov, by phone at 1-800-MEDICARE, by mail, or directly through the insurance company offering the plan.
Your coverage starts on January 1 if you enroll by December 7, or on the first of the month following your enrollment outside the Annual Enrollment Period.
If you miss the Annual Enrollment Period and do not may have access to for a Special Enrollment Period, you cannot join a Medicare Advantage plan until the following October.

Check your enrollment window before you start

The Annual Enrollment Period runs October 15 through December 7 each year. If you enroll during this window, your coverage begins January 1. This is the main enrollment period, and most people use it.

If you do not enroll during the Annual Enrollment Period, you may still be able to join if you have a may have access to life event. These include turning 65, losing employer coverage, moving to a new state, getting married or divorced, or becoming a U.S. citizen. A Special Enrollment Period typically lasts 60 days from the date of your may have access to event. You will need to prove the event occurred — for example, a notice from your employer that coverage ended, or a marriage certificate.

If you miss both windows and have no may have access to event, you cannot join a Medicare Advantage plan until the next Annual Enrollment Period. This is a hard important date, so mark your calendar now if you are outside the enrollment window.

Gather your documents and plan information

Before you enroll, have these items ready: your Medicare card, your Social Security number, and information about any current health coverage (such as employer coverage or Medicaid). You will also need to know which plan you want to join.

To find plans available in your area, visit Medicare.gov and use the plan finder tool. You can search by your ZIP code and see which Medicare Advantage plans are offered near you, what they cost, which doctors and hospitals they cover, and what prescription drugs are included. Write down the plan name and the insurance company name — you will need both when you enroll.

If you take prescription medications, check the plan's formulary (the list of covered drugs) to make sure your medications are included. If a drug you need is not covered, contact the insurance company to ask about exceptions or alternative drugs the plan does cover.

Enroll through Medicare, your insurance company, or by mail

You have four ways to enroll in a Medicare Advantage plan. The fastest is usually online through Medicare.gov: go to the plan finder, select your plan, and follow the prompts to complete enrollment. You will receive a confirmation email and your plan documents will arrive by mail.

You can also call 1-800-MEDICARE (1-800-633-4227) and speak to a representative who will help you enroll over the phone. This takes about 20 to 30 minutes. Have your Medicare card and plan information in front of you when you call.

A third option is to contact the insurance company directly. Find the phone number on Medicare.gov or on the plan's website, call them, and tell them you want to enroll. They will walk you through their enrollment process.

Finally, you can enroll by mail. read the CMS-10003 form from Medicare.gov, fill it out, and mail it to the address listed on the form. Mail enrollment takes longer — allow two to three weeks for processing — so use this method only if you cannot enroll online or by phone.

Understand your coverage start date

Your coverage start date depends on when you enroll. If you enroll between October 15 and December 7, your coverage begins January 1 of the following year. If you enroll outside the Annual Enrollment Period (during a Special Enrollment Period), your coverage usually starts on the first day of the month after you enroll, or sometimes the first day of the second month after you enroll — the insurance company will tell you the exact date when you enroll.

Until your Medicare Advantage coverage starts, you remain on your current coverage. If you were on Original Medicare, you stay on Original Medicare. If you had employer coverage, that coverage continues until your Medicare Advantage plan begins. Do not cancel any coverage until you confirm your new plan has started.

What happens after you enroll

After you submit your enrollment, the insurance company will send you a welcome packet by mail within two weeks. This packet includes your member ID card, plan documents, and information about how to use your coverage. Keep your member ID card with you — you will need it at the doctor's office and the pharmacy.

Before your coverage starts, review the plan documents to understand your costs: what your monthly premium is, what your deductible is (if any), what you pay for doctor visits and hospital stays, and whether you need referrals to see specialists. If you have questions, call the insurance company's member services line — the number is on your welcome packet.

If you change your mind after enrolling, you have a limited window to disenroll. During the Annual Enrollment Period, you can switch to a different Medicare Advantage plan or go back to Original Medicare anytime between October 15 and December 7. Outside that window, you have only 30 days from the date you receive your welcome packet to cancel and return to Original Medicare.

Common mistakes to avoid

The most common mistake is waiting until after December 7 to enroll and then discovering you have no may have access to event for a Special Enrollment Period. If this happens, you cannot join a Medicare Advantage plan until the following October. Mark your calendar now and enroll during the Annual Enrollment Period if you are interested.

A second mistake is enrolling in a plan without checking whether your current doctors and hospitals are in the plan's network. Medicare Advantage plans have networks — lists of doctors and hospitals you can use. If your doctor is not in the network, you may have to pay more or switch doctors. Always check the plan's provider directory on Medicare.gov or call the insurance company before you enroll.

A third mistake is not reviewing the plan's formulary for your prescription drugs. Some Medicare Advantage plans cover different drugs than others. If your medications are not on the plan's formulary, you may have to pay out of pocket or switch to a different drug. Check this before you enroll.

Frequently Asked Questions

Can I enroll in Medicare Advantage if I have not turned 65 yet?

No. You must be 65 or older and enrolled in Medicare Part A and Part B to join a Medicare Advantage plan. If you are under 65 and have Medicare due to disability or end-stage renal disease, you can enroll once you have been on Medicare for at least 24 months.

What if I miss the December 7 important date?

If you miss the Annual Enrollment Period and do not have a may have access to life event, you cannot join a Medicare Advantage plan until the next October 15. may have access to events include turning 65, moving to a new state, losing other coverage, or becoming a U.S. citizen. You have 60 days from the event to enroll.

Can I switch Medicare Advantage plans after I enroll?

Yes, but only during the Annual Enrollment Period (October 15 to December 7) or if you have a may have access to life event. Outside these windows, you are locked into your plan for the year. If you want to switch, you must wait until the next Annual Enrollment Period.

Do I need to cancel Original Medicare when I enroll in Medicare Advantage?

No. When you enroll in a Medicare Advantage plan, Medicare automatically disenrolls you from Original Medicare. You do not need to take any action to cancel it. However, if you have a Medigap policy (supplemental insurance), you should contact that insurance company to cancel it, as you cannot use both Medigap and Medicare Advantage at the same time.

What if my plan is discontinued or I move out of the service area?

If your plan ends or you move outside its service area, you may have access to for a Special Enrollment Period. You have 60 days to join a different Medicare Advantage plan or return to Original Medicare. The insurance company or Medicare will notify you if this happens.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.