Medicare Supplement

How Medigap Works for Medicare Enrollees in Sioux Falls

Sioux Falls, South Dakota — If you've ever looked at Medicare Supplement options and felt like you were staring at a bowl of alphabet soup, you're not alone. Plans labeled A, B, D, G, K, L, M, and N — what do those letters actually mean? Here's a plain-language walk-through of how Medigap works, why the letters are standardized, and where to turn for answers you can trust.

What Medigap actually does

Medicare Supplement Insurance — nicknamed Medigap — is private insurance that works alongside Original Medicare (Part A and Part B). It doesn't replace Medicare. Instead, it helps pay some of the out-of-pocket costs that Original Medicare leaves behind, like coinsurance, copayments, and certain deductibles.

So the order goes: Medicare pays its share first, then your Medigap policy picks up some or all of what's left, depending on which lettered plan you own.

One important note: Medigap is different from Medicare Advantage (Part C). You can't have both at the same time. Medigap is designed to pair with Original Medicare, not with an Advantage plan.

Why the letters exist

Back in the early 1990s, the federal government stepped in to make Medigap shopping less confusing. Insurance companies were selling dozens of different policies with different rules, and consumers couldn't tell them apart.

The fix was standardization. Today, in most states — including South Dakota — Medigap policies come in a set list of lettered plans. Every insurance company that sells "Plan G," for example, has to offer the exact same core benefits as every other company's "Plan G." Only the price and the customer service can differ.

That's the point of the letters: they let you compare apples to apples.

What each letter roughly covers

The currently available Medigap plans for new enrollees are A, B, D, G, K, L, M, and N. Plans C and F are still held by people who were eligible for Medicare before January 1, 2020, but they're closed to newly eligible beneficiaries.

Here's the general idea, without getting into specific dollar amounts:

• Plans A and B cover a smaller set of gaps.
• Plan G is one of the most comprehensive options available to new enrollees.
• Plan N offers broad coverage but asks you to pay some small copays for office and ER visits.
• Plans K and L have lower premiums but require you to pay a share of costs until you hit an out-of-pocket limit.
• Plan M falls somewhere in the middle.

For a side-by-side chart showing exactly what each letter covers, Medicare.gov keeps an up-to-date grid you can print or view on your phone.

What Medigap doesn't do

Medigap does not include prescription drug coverage. If you want help paying for medications, you'd typically add a stand-alone Part D drug plan.

That matters more than ever in 2026, because Part D has some meaningful updates:

• The new $2,100 out-of-pocket cap on covered prescription drugs applies to Part D enrollees.
• The maximum Part D deductible is $615.
• The old "donut hole" coverage gap is gone as of 2025 — Part D now has three phases instead of four.
• The Medicare Prescription Payment Plan lets you spread your drug costs into monthly installments if that helps your budget.

Higher-income beneficiaries should also know about IRMAA, the income-related surcharge that begins above $109,000 for single filers in 2026 and can raise both Part B and Part D premiums.

What's specific to Sioux Falls

Sioux Falls is in Minnehaha County, where beneficiaries have access to multiple insurance companies that sell standardized Medigap policies. Because the benefits of each lettered plan are set by federal rules, the plan itself won't be different in Sioux Falls than it would be in Rapid City or Sturgis. What can differ locally is which carriers are active in the market and what they charge.

South Dakota also has its own rules about when insurers must sell you a Medigap policy without medical underwriting — most notably during your six-month Medigap Open Enrollment Period, which starts the month you're 65 and enrolled in Part B. Missing that window can make it harder (or more expensive) to switch plans later, so it's worth marking on the calendar.

Where the letters fit in the Medicare calendar

Medigap has its own enrollment rules and isn't tied to the fall Annual Enrollment Period. But two Medicare-wide dates are still worth knowing:

• October 15 – December 7: Annual Enrollment Period for Medicare Advantage and Part D changes.
• January 1 – March 31: Medicare Advantage Open Enrollment, for folks already in an Advantage plan.

Medigap changes can generally be requested any time of year, but whether an insurer has to accept you depends on your situation.