Medicare Supplement

Understanding Medigap: What Those Plan Letters Really Mean

MESA, Ariz. — If you've started shopping for a Medicare Supplement policy, you've probably run into a wall of letters: Plan A, Plan G, Plan N, Plan K. It can feel like alphabet soup. The good news for Mesa residents sorting through their options is that those letters aren't random — they're standardized by federal law, and once you understand the system, comparing policies becomes much simpler.

Here's a plain-language guide to what Medigap does, how the letters work, and where to get trustworthy help.

What Medigap actually does

Medicare Supplement Insurance — commonly called Medigap — is private insurance that works alongside Original Medicare (Part A and Part B). It doesn't replace Medicare. Instead, it helps pay some of the out-of-pocket costs Original Medicare leaves behind, like coinsurance, copayments, and in some cases the Part A hospital deductible.

A few key points to keep in mind:

• Medigap only works with Original Medicare, not with Medicare Advantage plans.
• Medigap policies generally do not include prescription drug coverage. For that, most people add a separate Part D plan.
• You pay a monthly premium to the private insurer, in addition to your Part B premium.

Why the plan letters exist

Before the 1990s, Medigap policies varied wildly, and shopping was confusing. Congress standardized them so that a Plan G from one insurer covers the same benefits as a Plan G from another. What can differ is the price, the customer service, and whether the insurer offers extras like discounts or wellness perks.

In most states, including Arizona, Medigap policies are sold using the same set of standardized letters: A, B, C, D, F, G, K, L, M, and N. (Massachusetts, Minnesota, and Wisconsin have their own systems.)

What the letters cover — in general terms

Each lettered plan covers a specific mix of gaps in Original Medicare. Some highlights, without getting into any one insurer's pricing:

• Plan A offers the most basic set of benefits every Medigap plan must include.
• Plans B through N build on that with additional coverage, such as help with the Part A deductible, skilled nursing coinsurance, or foreign travel emergencies.
• Plans K and L have lower premiums but cap your out-of-pocket costs and share coinsurance differently.
• Plans C and F are only available if you became eligible for Medicare before January 1, 2020. Newer enrollees can't buy them.
• Plan G and Plan N are among the most commonly purchased plans for people newly eligible.

You can see a side-by-side benefits chart on Medicare.gov — it's the clearest way to compare what each letter includes.

Timing matters: the Medigap Open Enrollment Period

One of the most important things to understand about Medigap is when you can buy it without medical underwriting.

Your Medigap Open Enrollment Period is a one-time, six-month window that starts the month you're 65 or older and enrolled in Part B. During this window, insurers must sell you any Medigap policy they offer at their best available rate, regardless of your health history.

Outside that window, in most states, insurers can ask health questions and either charge more or decline coverage. Arizona generally follows federal rules here, so Mesa residents should pay close attention to this timing.

How this fits with other 2026 Medicare changes

Even if you stay with Original Medicare and Medigap, other parts of Medicare are shifting in 2026:

• The Part D out-of-pocket cap is $2,100 for 2026.
• The Part D maximum deductible is $615.
• The coverage gap ("donut hole") was eliminated as of 2025; Part D now has three phases.
• The Medicare Prescription Payment Plan lets you spread drug costs across monthly payments if that helps your budget.
• IRMAA surcharges — extra premiums for higher earners — begin above $109,000 in income for a single filer in 2026.

Mesa is in Maricopa County, where beneficiaries have a wide range of stand-alone Part D and Medicare Advantage plans available. Availability and plan counts are set at the county level, so what's offered in Mesa is the same as what's offered elsewhere in Maricopa County.

Key enrollment dates to remember

• Medicare Annual Enrollment Period: October 15 – December 7 (for Part D and Medicare Advantage changes).
• Medicare Advantage Open Enrollment: January 1 – March 31 (for people already in a Medicare Advantage plan).
• Medigap Open Enrollment: the six months starting when you're 65 and enrolled in Part B — this one is personal to you.