Medicare Supplement

Medigap in Madison: What Those Letter Plans Actually Cover

MADISON, Wis. — If you've ever squinted at a chart of Medigap plans labeled A, B, D, G, K, L, M and N and wondered why the alphabet went off the rails, you're not alone. Medicare Supplement insurance — often called Medigap — is one of the most useful, and most misunderstood, pieces of the Medicare puzzle.

Here's a plain-language look at what Medigap does, what it doesn't, and how those standardized letter plans work for people on Original Medicare in the Madison area.

What Medigap is (and isn't)

Medigap is private insurance you can buy to help pay some of the out-of-pocket costs that Original Medicare (Part A and Part B) leaves behind — things like coinsurance, copayments, and deductibles. It works alongside Original Medicare, not instead of it.

A few important things Medigap is not:

• It is not Medicare Advantage (Part C). You can't have both a Medigap policy and a Medicare Advantage plan at the same time.
• It does not include prescription drug coverage. For drugs, you'd add a separate Part D plan.
• It generally does not cover dental, vision, hearing aids, or long-term care.

According to Medicare.gov, Medigap policies sold today are standardized by the federal government, which is what makes those letters so important.

How the standardized letters work

In most states — including Wisconsin, with one wrinkle we'll get to — Medigap plans are sold under letter names: 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: every Plan G sold by every insurer covers the exact same set of benefits. Same with Plan N, Plan K, and so on. The letter tells you what's covered. The insurance company decides the premium, the customer service, and how the policy is administered — but not the benefits.

That means if you're comparing Plan G from one carrier to Plan G from another, you're really comparing price, company reputation, and service — not coverage.

The Wisconsin twist

Here's where Madison readers need to pay extra attention. Wisconsin is one of three states — along with Minnesota and Massachusetts — that standardizes its Medigap plans differently than the rest of the country.

Instead of the letter system, Wisconsin uses a base plan that all insurers must offer, plus optional riders you can add to build out coverage (for example, riders for the Part A deductible, Part B copayment, or additional home health care).

So if you're shopping in Dane County and a friend in Florida tells you about "Plan G," the direct comparison doesn't quite work. You'll want to ask insurers how their Wisconsin base plan and riders line up with what you need. Wisconsin's Office of the Commissioner of Insurance publishes a consumer guide that walks through the state's Medigap structure in detail.

When you can buy a Medigap policy

Timing matters a lot with Medigap. Your Medigap Open Enrollment Period is a six-month window that starts the month you're 65 or older and enrolled in Part B. During that window, insurers must sell you any Medigap policy they offer at their best available rate, and they can't turn you down or charge you more because of your health.

Outside that window, in most cases, insurers can use medical underwriting — meaning they can review your health history and either decline coverage or charge a higher premium. There are some limited "guaranteed issue" situations, but they're narrower than many people realize.

This is why counselors often say: don't miss your Medigap Open Enrollment window if you think you'll want a supplement policy at any point.

Medigap vs. Medicare Advantage — a quick reality check

Madison is in Dane County, where beneficiaries have a healthy number of Medicare Advantage plans to choose from during Annual Enrollment (October 15 – December 7). Advantage plans bundle Parts A, B, and usually D, and often include extras — but they use provider networks and have their own cost-sharing rules.

Medigap goes a different direction: you stay on Original Medicare, use any provider in the U.S. that accepts Medicare, and use the supplement to smooth out those cost-sharing bills. Neither path is universally "better" — they're built differently, and the right fit depends on your budget, your doctors, your prescriptions, and how you feel about predictability versus flexibility.

What Medigap still won't pay for

Even a robust Medigap policy doesn't cover everything. You'll still need to plan separately for:

• Prescription drugs — that's Part D, with a new $2,100 annual out-of-pocket cap in 2026 and a maximum deductible of $615.
• Routine dental, vision, and hearing.
• Long-term custodial care (nursing home stays that aren't skilled care).
• Care outside the U.S., in most cases, though some Medigap plans include limited foreign travel emergency coverage.