Medicare Supplement

Medigap letters A, G, and N explained for Jefferson City

JEFFERSON CITY, Mo. — Original Medicare covers a lot, but it doesn't cover everything. That's where Medicare Supplement Insurance — better known as Medigap — comes in. If you've ever looked at a Medigap brochure and felt lost in a sea of letters like A, G, and N, you're not alone. Here's a plain-English guide to what Medigap does and why those letters matter.

What Medigap Actually Does

Medigap is private insurance that works alongside Original Medicare (Part A and Part B). It helps pay some of the out-of-pocket costs Medicare leaves behind — things like coinsurance, copayments, and deductibles.

To buy a Medigap policy, you generally need to already be enrolled in Part A and Part B. Medigap does not work with Medicare Advantage plans; it's designed to pair with Original Medicare only. And Medigap policies don't include prescription drug coverage — for that, you'd add a separate Part D plan.

Why the Letters Exist

Here's the part that trips people up: Medigap plans are standardized by the federal government. That means a Plan G sold by one insurance company covers the exact same benefits as a Plan G sold by any other company in your state. (Massachusetts, Minnesota, and Wisconsin standardize their plans a little differently.)

In most states, there are 10 standardized plan letters: A, B, C, D, F, G, K, L, M, and N. Each letter represents a fixed package of benefits. The company selling the plan can change the price and the customer service — but not what's covered.

That's actually good news for shoppers. Once you decide which letter fits your needs, comparing plans becomes mostly a matter of comparing prices and the insurer's reputation.

What Changed with Plans C and F

If you became eligible for Medicare on or after January 1, 2020, you cannot buy Plans C or F. These two plans covered the Part B deductible, and federal law now blocks new enrollees from choosing plans that pay that deductible for them.

People who were already eligible for Medicare before 2020 can still keep or buy Plans C and F where available. For most newer enrollees, Plan G has become the closest equivalent — it covers almost everything Plan F did, except that Part B deductible.

The Best Time to Buy

Timing matters a great deal with Medigap. Your Medigap Open Enrollment Period is a one-time, six-month window that starts the month you're 65 or older and enrolled in Part B. During that window, insurance companies must sell you any Medigap plan they offer at their best available rate, regardless of your health history.

Miss that window, and in most states insurers can use medical underwriting — meaning they can charge you more or turn you down based on your health. This is one of the most important deadlines in all of Medicare, and it's easy to overlook.

How Medigap Fits with the Rest of Medicare

Medigap is one path. Medicare Advantage (Part C) is another. You can't use both at the same time. Jefferson City is in Cole County, where residents on Original Medicare can shop Medigap policies from any insurer licensed to sell them in Missouri.

Keep in mind that Medigap is separate from your drug coverage. For 2026, Part D has a $2,100 out-of-pocket cap on covered prescriptions and a maximum deductible of $615, according to CMS. The coverage gap (the old "donut hole") was eliminated in 2025, so Part D now has three phases instead of four. There's also an optional Medicare Prescription Payment Plan that lets you spread drug costs across the calendar year in monthly payments.