Medicare Supplement

How Medigap's Lettered Plans Work: A Plain-English Guide

ISSAQUAH, Wash. — If you're new to Medicare, the alphabet soup of Medigap plans can feel confusing. Plan A, Plan G, Plan N — what do the letters mean, and why do two different insurance companies sell "the same" Plan G? Here's a plain-English look at how Medicare Supplement Insurance works and why those letters matter.

What Medigap actually does

Medigap, also called Medicare Supplement Insurance, is a private policy that works alongside Original Medicare (Part A and Part B). After Medicare pays its share of a covered service, your Medigap plan helps pay some of what's left — things like coinsurance, copayments, and deductibles.

A few important points, according to Medicare.gov:

• You must be enrolled in Part A and Part B to buy a Medigap policy.
• Medigap does not work with Medicare Advantage. You choose one path or the other.
• Medigap generally does 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 there are letters

In most states, Medigap plans are standardized by the federal government. That means the benefits inside "Plan G" from one company must match "Plan G" from another. The letter tells you exactly what the plan covers.

Currently, Medigap plans are labeled 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.) Each letter offers a different mix of cost-sharing help. For example, some letters cover the Part A hospital deductible in full, while others cover only a portion.

Because the benefits are standardized, the main things that vary between companies selling the same letter are:

• The monthly premium
• Customer service and how the company handles claims
• Extra perks the insurer chooses to add on top

Shopping the letter, not the logo

Since a Plan G is a Plan G no matter who sells it, comparison shopping usually comes down to price and the company's reputation. Issaquah is in King County, Washington, where multiple insurers offer Medigap policies. Medicare's official plan finder at medicare.gov lets you look up which insurers sell each letter in your ZIP code and see current premium ranges.

Washington state also has some unique Medigap rules that can make switching plans easier than in most states. A local SHIP counselor can walk you through what applies in your situation.

When you can buy in — and why timing matters

The best window to buy Medigap is your Medigap Open Enrollment Period: a one-time, six-month window that starts the month you turn 65 and are enrolled in Part B. During this window, insurance companies cannot deny you a policy or charge you more because of health problems.

Outside that window, insurers in most states can use medical underwriting, which may affect whether you qualify or what you pay. This is why many people who want Medigap sign up as soon as they're eligible.

How Medigap fits with the rest of Medicare in 2026

Medigap doesn't cover prescription drugs, so it helps to know what's happening on the Part D side in 2026:

• The Part D out-of-pocket cap is $2,100 for 2026.
• The Part D maximum deductible is $615.
• The old "donut hole" coverage gap was eliminated in 2025; Part D now has three phases.
• The Medicare Prescription Payment Plan lets you spread drug costs across the year in monthly installments if you choose.
• IRMAA surcharges for higher-income enrollees begin above $109,000 in income for a single filer in 2026.

Key dates to remember: the Annual Enrollment Period runs October 15 – December 7, and the Medicare Advantage Open Enrollment Period runs January 1 – March 31. Note that Medigap has its own enrollment rules and isn't tied to these windows.