Medicare Supplement

Medigap letters from A to N: a Rochester explainer

ROCHESTER, N.Y. — If you've spent any time reading about Medicare, you've probably run into a wall of letters: Plan A, Plan G, Plan N, Plan K. Those are Medicare Supplement plans, also called Medigap. And once you understand how the lettering system works, the choices get a lot less intimidating.

What Medigap is — and what it isn't

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 — things like coinsurance, copayments, and in some cases the Part A deductible.

One important thing to know up front: Medigap is different from Medicare Advantage. You can't have both at the same time. Medigap pairs with Original Medicare; Medicare Advantage (Part C) is a separate way of getting your Medicare benefits through a private plan.

Why the letters exist

Before the early 1990s, shopping for a Medicare supplement was a mess. Every insurance company sold its own version, and comparing them was nearly impossible.

To fix that, the federal government stepped in and standardized the plans. Today, in most states, Medigap plans are labeled with letters — A, B, C, D, F, G, K, L, M, and N. Each letter represents a fixed set of benefits set by law. That means Plan G from one insurance company covers the exact same things as Plan G from another company. The price can differ, and customer service can differ, but the benefits inside the letter are identical.

For details straight from the source, Medicare.gov has a plain-language breakdown of what each letter covers.

How the letters actually differ

Think of the letters as a menu of coverage levels, from lighter to more comprehensive.

• Plan A offers the most basic set of benefits every Medigap plan must include.
• Plans B through N add more coverage in different combinations — for example, help with the Part A deductible, skilled nursing coinsurance, or foreign travel emergency coverage.
• Plans K and L use a cost-sharing approach, where you pay a percentage until you hit an annual out-of-pocket limit.
• Plan N has small copays for some office and ER visits in exchange for lower premiums.

A key note: Plans C and F are no longer sold to people who became eligible for Medicare on or after January 1, 2020. If you were eligible before that date, you may still be able to buy them. This was a federal change tied to how the Part B deductible is handled.

What Medigap does not cover

Medigap plans generally don't include prescription drug coverage. If you want help paying for medications, you'd typically add a stand-alone Part D drug plan.

That matters more than ever in 2026, because Part D now has a $2,100 annual out-of-pocket cap on covered drugs, and the maximum Part D deductible is $615. The old "donut hole" coverage gap was eliminated in 2025, so drug costs now move through just three phases. Medicare also offers the optional Medicare Prescription Payment Plan, which lets you spread your drug costs across the year in monthly payments.

Medigap also doesn't cover routine dental, vision, hearing aids, or long-term custodial care.

Timing matters: the Medigap Open Enrollment window

The single most important thing to understand about buying Medigap is timing.

You get a six-month Medigap Open Enrollment Period that starts the month you're 65 and enrolled in Part B. During that window, insurance companies can't turn you down or charge you more based on your health. Outside that window, in most states, they generally can — so a health condition that develops later could make switching plans harder or more expensive.

New York has some of the more consumer-friendly Medigap rules in the country, but the safest strategy for anyone is still to understand your options before that six-month window closes.

A quick word on where you live

Rochester is in Monroe County, and Medicare plan availability is set at the county level. The count of Medigap carriers licensed to sell in New York is separate from the Medicare Advantage and Part D plan counts you'll see quoted locally. If you want a personalized look at what's available in Monroe County, the Plan Finder tool at Medicare.gov lets you search by ZIP code.