Medicare Advantage

Medicare Supplement Coverage Basics for Phoenix Residents

For 2027, Phoenix is looking at 92 Medicare Advantage plans: 17 new, 13 gone since 2026, and 33 still here but changed on premium, deductible, plan type or name, 13 of them under a new name. Below, how the lineup shifted in Maricopa County and what to compare, with no plan ranked or recommended.

PHOENIX — The calendar just turned, and with it a short but powerful door opens for people already enrolled in a Medicare Advantage plan. From January 1 through March 31, the Medicare Advantage Open Enrollment Period lets you make one change if your current plan isn’t working out. Miss it, and in most cases you’re locked in until the fall.

That timing matters here. Phoenix is in Maricopa County, where Medicare Advantage choices are unusually broad — 79 plans from 16 carriers for 2027 — and many Valley residents finalized 2027 coverage during the fall Annual Enrollment Period without really test-driving it. The winter window is a chance to course-correct.

What this window is — and what it isn’t

The Medicare Advantage Open Enrollment Period (often called MA-OEP) is narrow on purpose. According to CMS, it applies only if you were enrolled in a Medicare Advantage plan as of January 1. If you’re on Original Medicare only, this window is not for you.

During MA-OEP you can do one of two things, one time:

• Switch from your current Medicare Advantage plan to a different Medicare Advantage plan.
• Drop your Medicare Advantage plan, return to Original Medicare (Parts A and B), and add a stand-alone Part D drug plan.

You cannot use this window to join a Medicare Advantage plan for the first time from Original Medicare, and you cannot use it to pick up a stand-alone Part D plan if you’re staying on Original Medicare.

Why the first 90 days of the year matter

Most people don't truly know how their plan works until they use it. January is when the new plan year kicks in — new provider networks, new drug formularies, new prior-authorization rules. Phoenix retirees often discover in those first weeks that a preferred doctor at Banner or HonorHealth isn't in-network the way they expected, or that a maintenance medication landed in a different cost tier.

That’s the exact problem MA-OEP was designed to fix. You get a second look after real-world use.

How the dates line up across the year

It helps to see the full calendar in order:

• October 15 – December 7 (Annual Enrollment Period): Anyone with Medicare can join, switch, or drop Medicare Advantage or Part D plans. Changes take effect January 1.
• January 1 – March 31 (Medicare Advantage Open Enrollment): One change, for current MA enrollees only. Changes generally take effect the first of the following month.
• Special Enrollment Periods (year-round, if you qualify): Triggered by events like moving, losing other coverage, or qualifying for Extra Help.
• General Enrollment Period (January 1 – March 31): A different window, for people who missed signing up for Part B when first eligible.

Two of those overlap in the same three months, which is a common source of confusion. MA-OEP is about switching plans; the General Enrollment Period is about first-time Part B sign-up.

What happens if you miss March 31

If March 31 passes and you haven't made a change, your Medicare Advantage plan is generally your coverage for the rest of the year. The next chance to switch, for most people, is the Annual Enrollment Period starting October 15, with those changes taking effect January 1, 2028.

The main exception is a Special Enrollment Period. Common triggers include:

• Moving to a new address outside your plan’s service area (or into one with new options).
• Losing employer or union coverage.
• Entering, living in, or leaving a nursing facility.
• Becoming eligible for Medicaid or the Extra Help program for drug costs.

If any of those apply, you may have rights to change plans outside the standard windows. A quick call to 1-800-MEDICARE or Arizona’s SHIP (the State Health Insurance Assistance Program) can confirm whether you qualify.

A quick word on drug coverage for 2027

Even if you're happy with your medical plan, the drug side of Medicare continues to evolve. The Part D out-of-pocket cap is $2,100 in 2026 and $2,400 in 2027, and the maximum Part D deductible is $615 in 2026 and $700 in 2027. The old coverage gap ("donut hole") is gone — replaced by a simpler three-phase structure that took effect in 2025. There's also the Medicare Prescription Payment Plan, which lets you spread drug costs across the year in monthly installments instead of paying a big bill at the pharmacy counter.

None of those changes require you to switch plans. But if your prescriptions changed or your plan’s formulary changed, MA-OEP is when you can act on it.

How to decide before the window closes

A few practical steps for Phoenix-area readers weighing a change:

1. Pull out your plan's 2027 Evidence of Coverage and Annual Notice of Change. 2. Confirm your doctors and preferred hospitals are in-network for the new plan year. 3. Check that every prescription is on the formulary and note its tier. 4. Use the Plan Finder tool at medicare.gov to compare options in Maricopa County. 5. If anything is unclear, talk to a SHIP counselor — the service is free and unbiased.