Medicare Supplement

Medigap Letter Plans A Through N Explained for Watertown

WATERTOWN, S.D. — If Original Medicare feels like it leaves too many blanks — the deductibles, the 20% coinsurance, the "what if I get really sick" worry — that's the gap Medicare Supplement insurance was designed to fill. And with the fall Annual Enrollment Period running Oct. 15 through Dec. 7, a lot of folks around Codington County are sitting at the kitchen table trying to sort out what Medigap does, what it doesn't, and how those mysterious letter plans (A through N) actually work.

Here's a plain-English guide.

What Medigap Is — and What It Isn't

Medicare Supplement insurance, also called 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. Think hospital coinsurance, the Part B 20%, extra hospital days, and — depending on the plan — the Part A deductible.

A few things Medigap is not:

• It is not Medicare Advantage (Part C). Advantage plans replace how you get your Medicare. Medigap works alongside Original Medicare.
• It does not include prescription drug coverage. For drugs, you'd add a separate Part D plan.
• It usually doesn't cover dental, vision, hearing aids, or long-term care.

You can't have a Medigap policy and a Medicare Advantage plan at the same time. It's one path or the other.

How the Standardized Letters Work

This is the part that trips people up. In most states, Medigap policies are standardized by the federal government into plans labeled with 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 Jan. 1, 2020.)

Here's the key idea: Plan G from one company covers the exact same things as Plan G from another company. The benefits are set by law. What can differ is the price, the customer service, and whether the company raises rates over time.

That means shopping Medigap is mostly about comparing:

1. Which letter plan fits how you use care. 2. Which insurer offers a fair price for that letter in your area. 3. How the company has handled rate increases in the past.

Massachusetts, Minnesota, and Wisconsin standardize their plans a little differently, but South Dakota follows the federal letter system.

The Best Time to Buy: Your Medigap Open Enrollment Window

This is the single most important sentence in this article: **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 can't turn you down or charge you more because of your health. Miss it, and in most states — South Dakota included — insurers can use medical underwriting. That means a health condition could lead to a higher premium or a denial.

This window is separate from the fall Annual Enrollment Period you hear about on TV. AEP (Oct. 15–Dec. 7) is for Medicare Advantage and Part D changes. Medigap has its own rules.

Where Medigap Fits With Part D and 2026 Changes

Because Medigap doesn't cover prescriptions, most people with a Supplement plan also enroll in a stand-alone Part D drug plan. A few 2026 program facts worth knowing:

• The Part D out-of-pocket cap is $2,100 in 2026. Once you hit it, you pay $0 for covered drugs the rest of the year.
• The maximum Part D deductible is $615.
• The old "donut hole" coverage gap is gone — Part D now has three phases.
• The Medicare Prescription Payment Plan lets you spread drug costs across the calendar year in monthly installments instead of paying big amounts at the pharmacy counter.
• IRMAA — the income-related surcharge on Part B and Part D — kicks in above $109,000 for a single filer in 2026.

Watertown Context

Watertown is in Codington County, where beneficiaries can choose between staying on Original Medicare (often paired with a Medigap policy and a Part D plan) or enrolling in a Medicare Advantage plan. Medigap availability and pricing are regulated at the state level in South Dakota, while Medicare Advantage and Part D options are set at the county level. If you want to know exactly which insurers sell which lettered Medigap plans in South Dakota, the state's Division of Insurance and Medicare.gov both publish that list.