If you are turning 65 in Arizona or Alabama, you have one big decision to make: Medicare Advantage or a Medicare Supplement plan (also called Medigap). Both fill gaps in Original Medicare, but they work in completely different ways. Here is a plain-English comparison, plus what is specific to each state in 2026.
First, the gap you are filling
Original Medicare (Part A for hospital, Part B for medical) covers a lot, but not everything. You still owe deductibles and 20 percent coinsurance on most Part B services, and there is no annual cap on what you can spend out of pocket. That is the gap both options exist to fill.
How Medicare Advantage works
A Medicare Advantage plan (Part C) replaces Original Medicare. A private insurance company bundles your Part A and Part B benefits, usually adds prescription drug coverage, and often includes extras like dental, vision, and hearing. Most plans use a network (HMO or PPO), so which doctors you can see matters.
Premiums are low, and many plans in both states charge $0 per month on top of your Part B premium. The tradeoff is that you pay copays as you go, and you must use the plan's network and follow its rules, such as prior authorization for some services.
How Medigap works
A Medigap plan supplements Original Medicare instead of replacing it. You keep Original Medicare and see any doctor in the country who accepts it, no networks and no referrals. The Medigap policy then pays most or all of your share, depending on the plan letter you pick (Plan G and Plan N are the most popular). You pay a higher monthly premium in exchange for very predictable costs. Medigap does not include drug coverage, so most people pair it with a standalone Part D plan.
The key differences at a glance
- Monthly cost: Medicare Advantage premiums are low or $0. Medigap premiums are higher but your out-of-pocket costs are small and predictable.
- Doctor access: Medigap works with any provider that accepts Medicare nationwide. Medicare Advantage uses networks that are usually local or regional.
- Drug coverage: usually built into Medicare Advantage. With Medigap you add a separate Part D plan.
- Extras: Medicare Advantage often includes dental, vision, and hearing. Medigap does not.
- Switching later: you can join or change Medicare Advantage plans every year. Getting a Medigap plan after your initial window usually requires health underwriting, and you can be declined.
What is specific to Arizona
Arizona retirees, especially in Maricopa and Pima counties, have a deep bench of Medicare Advantage plans, including many $0-premium options. Arizona has no special state rule for switching Medigap plans (some states have a birthday rule, but Arizona does not), so the standard federal windows apply. If you are on Medicare under age 65 due to disability, Medigap options in Arizona are extremely limited, so a Medicare Advantage plan is often the practical route until you turn 65.
What is specific to Alabama
Alabama has 98 Medicare Advantage plans available statewide in 2026, up from 93 in 2025, and the average Medicare Advantage premium in the state fell from $15.76 to $10.62. That statewide number is not what you will see on your own screen, though: the count available in any single Alabama county runs from roughly 36 to 67, so what matters is your county, not the state total. Rural Alabama residents should look closely at provider networks before choosing Medicare Advantage, since some networks thin out away from Birmingham, Huntsville, and Mobile. Medigap can be attractive there for exactly that reason. Like Arizona, Alabama does not guarantee Medigap access for people under 65, so insurers can decline or charge more based on health.
The deadline that matters most
When you enroll in Part B at 65, you get a one-time, six-month Medigap open enrollment window. During those six months, insurers must sell you any Medigap plan regardless of your health history. After the window closes, they can ask health questions and say no in both Arizona and Alabama. If you think you may ever want Medigap, this window is the time to decide.
Medicare Advantage, by contrast, has yearly chances to enroll or switch: the Annual Enrollment Period from October 15 to December 7, and the Medicare Advantage Open Enrollment Period from January 1 to March 31 for people already on an Advantage plan.