Medicare Supplement

How Medigap's Lettered Plans Actually Work in 2026

HAYWARD, Calif. — If you've ever tried to compare Medicare Supplement plans and felt like you were reading a bowl of alphabet soup, you're not alone. Plans go by single letters — A, B, D, G, K, L, M, N — and the naming can feel random. It isn't. Those letters are a federal shorthand that makes it easier, not harder, to shop.

Here in Hayward, where thousands of Alameda County residents are already on Medicare or aging into it, understanding what a Medigap plan is (and isn't) can save a lot of confusion during Medicare's fall Annual Enrollment Period, which runs October 15 through December 7.

What Medigap actually does

Original Medicare pays for a big share of your hospital and doctor costs, but not all of it. There are deductibles, coinsurance, and copays that can add up — especially if you have a hospital stay or an ongoing condition.

A Medigap policy (also called Medicare Supplement Insurance) is a private policy that helps pay some of those leftover costs. It rides alongside Original Medicare. When you get care, Medicare pays first, then your Medigap policy pays its share of what's left.

Medigap does not replace Medicare. It fills gaps in it — hence the nickname.

Why the plans are named by letters

Back in 1990, Congress standardized Medigap so shoppers could compare apples to apples. Today, in most states, there are up to 10 standardized plans identified by letters: 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.)

Here's the key idea: the benefits inside each lettered plan are set by federal rules. A Plan G sold by Insurer X covers the same gaps as a Plan G sold by Insurer Y. What can differ is the price, the customer service, and extras like discount programs — not the core coverage.

Massachusetts, Minnesota, and Wisconsin standardize their plans a little differently, but California — including Hayward — follows the standard lettered system.

What Medigap does not cover

This part trips people up, so it's worth being clear. Medigap policies generally do not cover:

• Prescription drugs (you'd add a separate Part D plan for that)
• Long-term care in a nursing home
• Routine dental, vision, or hearing care
• Hearing aids or eyeglasses

For drug coverage, remember the 2026 numbers: Part D now has a $2,100 annual out-of-pocket cap, a maximum deductible of $615, and the old "donut hole" coverage gap is gone — replaced by a simpler three-phase structure. There's also a Medicare Prescription Payment Plan that lets you spread your drug costs across the calendar year in monthly installments if that helps your budget.

Medigap and Medicare Advantage are an either/or

You can't have both. If you're enrolled in a Medicare Advantage plan (Part C), you can't also use a Medigap policy — and it's illegal for anyone to sell you one in that situation. Medigap works only with Original Medicare.

Hayward is in Alameda County, where residents have access to a range of Medicare Advantage plans as well as stand-alone Part D plans through Medicare's plan finder. Whether Original Medicare + Medigap + Part D makes more sense than a Medicare Advantage plan depends on your doctors, your medications, your travel habits, and your budget. Neither path is universally "better."

Timing matters more than most people realize

The single most important window for buying Medigap is your Medigap Open Enrollment Period — a one-time, 6-month window that starts the first month you're 65 or older and enrolled in Medicare Part B.

During that window, insurers must sell you any Medigap policy they offer at their best available rate, regardless of your health history. After it closes, in most states insurers can use medical underwriting, which means they can charge you more or turn you down based on preexisting conditions.

California does have some additional protections — including a "birthday rule" that lets current Medigap policyholders switch to an equal or lesser plan each year around their birthday without underwriting — but the initial 6-month window is still the cleanest opportunity.

A quick word on IRMAA

If your income is above $109,000 as a single filer in 2026 (or the corresponding threshold for joint filers), you'll pay an income-related surcharge called IRMAA on top of your Part B and Part D premiums. IRMAA doesn't affect Medigap premiums directly, but it's part of the bigger cost picture when you compare paths.

Where to get straight answers

Before you sign anything, use official sources:

• Medicare.gov has a plan comparison tool and a plain-English Medigap guide.
• 1-800-MEDICARE (1-800-633-4227) is staffed 24/7.
• California's SHIP program — called HICAP (Health Insurance Counseling and Advocacy Program) — offers free, unbiased one-on-one counseling. Alameda County residents can reach the local HICAP office by phone or online.