Medicare Supplement

Medigap standardized letters explained for Seattle shoppers

SEATTLE — If you've started shopping for a Medicare Supplement policy, you've probably noticed the letters: Plan A, Plan G, Plan N, and several more. Those letters aren't marketing labels. They're a federal shorthand that tells you exactly what a Medigap policy has to cover, no matter which insurance company sells it.

Here in Seattle, where thousands of King County residents age into Medicare each year, understanding those letters can make comparing policies a lot less confusing.

What Medigap actually does

Medicare Supplement Insurance, better known as Medigap, is private insurance that helps pay some of the out-of-pocket costs Original Medicare leaves behind — things like coinsurance, copayments, and the Part A hospital deductible. It's designed to sit alongside Original Medicare, filling the "gaps" the name suggests.

Medigap does not replace Medicare. You still have Parts A and B, and Medicare pays its share of the bill first. Your Medigap policy then picks up part or all of what's left, depending on which lettered plan you chose.

One important note: Medigap and Medicare Advantage are different roads. You can't use a Medigap policy to cover costs under a Medicare Advantage plan. You pick one lane or the other.

Why the letters exist

Before the plans were standardized, comparing supplement policies was a mess. Every company sold something a little different, and it was almost impossible to know if you were comparing apples to apples.

Today, in most states — including Washington — Medigap plans are standardized into lettered categories: A, B, C, D, F, G, K, L, M, and N. (Plans C and F are only available to people who became eligible for Medicare before January 1, 2020.) The federal government sets the benefits inside each letter, so a Plan G from one carrier covers the same core benefits as a Plan G from another carrier.

What can differ between companies:

• The monthly premium
• Customer service and extras like fitness perks
• How the premium is priced (by age, or the same for everyone in a group)

That last point matters in Washington, where the state has its own rules about how Medigap policies can be issued and switched. It's worth asking questions before you buy.

The best time to buy

The single most important date in Medigap shopping is the start of your Medigap Open Enrollment Period. It's a six-month window that begins the month you're 65 or older and enrolled in Part B. During this window, insurance companies can't turn you down or charge you more because of your health history.

Outside that window, in most cases, carriers can use medical underwriting, which may affect whether you can get a policy or what it costs. If you're already past that window and thinking about switching, check with Washington's SHIBA program (the state's SHIP counselor) before you make a move.

What Medigap does not cover

Medigap policies don't cover:

• Prescription drugs (you'd add a stand-alone Part D plan)
• Long-term care
• Vision, dental, and hearing services
• Private-duty nursing

For Part D in 2026, keep in mind the program-level figures: the annual out-of-pocket cap on covered drugs is $2,100, and the maximum Part D deductible is $615. The old "donut hole" coverage gap is gone, replaced by a simpler three-phase structure. If drug costs are a worry, Medicare also offers the Medicare Prescription Payment Plan, which lets you spread your drug costs across the year in monthly installments.

A quick Seattle snapshot

Seattle is in King County, where Medicare-eligible residents can choose Original Medicare (and add a Medigap policy plus a Part D plan) or enroll in a Medicare Advantage plan. King County generally has a wide range of both, and availability can shift each year during the Annual Enrollment Period, which runs October 15 through December 7.

Because Medigap is regulated at the state level, Washington residents have some flexibility other states don't. That's another reason to talk with a SHIBA counselor before locking in a decision.