How do I enroll in a Medicare Advantage plan?

What you need before you sign up for a Medicare Advantage plan, which enrollment windows you can use, and the five checks to run first.

Updated September 3, 2026 · 3 min read · by Gerino Alejos

Key points

You need both Part A and Part B before you can join a Medicare Advantage plan.
You can sign up with the plan, on Medicare.gov, or with a licensed agent, and the price is the same either way.
Run the five checks on your doctors, your hospital and your drugs before you sign, not after.

Signing up is quick once you are eligible. You need Part A and Part B first, and you have to be inside one of the enrollment windows. The work worth doing happens before you sign.

What you need first: Part A and Part B

Enrollment in both Part A, the hospital part, and Part B, which pays for doctor visits. Advantage requires both.
Your Medicare number and your Part A and Part B start dates, printed on your red, white and blue card.
A home address inside the plan's service area, the counties where that plan is sold.

If your Medicare card has not come yet, start there. See how to sign up for Medicare. Health history is not a barrier. See how Advantage plans treat conditions you already have.

When you can enroll

You can only join during a window.

Your Initial Enrollment Period, the seven months around your 65th birthday.
Annual Enrollment, October 15 to December 7, with coverage starting January 1.
Advantage Open Enrollment, January 1 to March 31, if you are already in an Advantage plan.
A special enrollment period, a window that opens after a life event. It applies if you moved, lost employer coverage, gained or lost Medicaid or Extra Help (help paying drug costs), or your plan left the area.

See all of the windows in one place.

Do these five checks before you enroll

Call the billing office at each of your doctors. Ask whether they are contracted with the exact plan name for the coming year.
Check the hospital your doctor admits to. Ask that hospital on its own.
Price your medicines on the plan's formulary, the list of drugs it covers, at your own pharmacy. Watch for a prior authorization flag, meaning the plan has to approve the drug first, or a step therapy flag, meaning you try another drug first.
Write down the yearly out of pocket maximum, the most the plan can ask you to pay in a year. That is your worst case.
A PPO (preferred provider organization) also covers some care outside its network of contracted doctors. On one, ask for the combined in and out of network maximum too.

Running these checks after you enroll is how January goes badly. Before, they take an afternoon.

The enrollment itself

You can sign up with the plan, on Medicare.gov, or with a licensed agent. The price is the same on all three routes. The premium, the monthly bill for the coverage, is set by the plan and filed with the Centers for Medicare and Medicaid Services. An agent adds nothing to your cost.

What an agent adds is the comparison across companies, and someone to call in February when something is denied. See how to compare Advantage plans.

After you enroll

You get a confirmation. Keep it, with the date and plan name.
Your member card arrives before coverage starts. Your Medicare card stays in your wallet too.
Your old Advantage or Part D plan ends on its own when the new one begins. You do not cancel it yourself.
Call your doctors' offices with the new plan information before your first visit.
Read the Evidence of Coverage, the booklet that spells out what the plan pays for, and check its prior authorization rules.

The decision to make before you enroll

If this is your first Medicare decision at 65, your six month Medigap window is running too. Medigap, or a supplement, is a policy that pays part of what Original Medicare leaves you. It does not come back.

Choosing Advantage now can mean a supplement is not open to you later on affordable terms. So look at both paths while both are still on the table. See the two side by side and the downsides of Advantage.

Run the five checks, pick your window, and enroll. To have someone go through your doctor and drug lists with you, call our McAllen office at (956) 687 3334, or enter your ZIP code in the plan pricing box on this page.

Common follow-up questions

Does using an agent cost more?

No. Plan premiums are filed with the Centers for Medicare and Medicaid Services. You pay the same whether you sign up with the plan, on Medicare.gov, or with a licensed agent.

Do I keep my red, white and blue Medicare card?

Yes. Keep it. You show the plan's member card at the doctor, but you are still enrolled in Medicare. You need it again if you go back to Original Medicare.

How long does enrollment take to process?

Usually a few weeks. Your coverage still starts on the effective date of your enrollment window. Your member card comes before that date.

Want this looked at properly?

We are an independent agency in McAllen serving Hidalgo, Cameron and Starr counties. There is no obligation to talk it through.

Call (956) 687 3334

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