Medicare Supplement

Medigap Plan Letters Explained: Avoid Costly Mix-Ups

MADISON, Miss. — If you're new to Medicare or helping a parent sort through mail, the Medigap alphabet can feel like a puzzle. Plans labeled A, B, D, G, K, L, M, and N — plus high-deductible versions — sit alongside Medicare Advantage brochures, and it's easy to confuse the two. Here's a plain-English guide to what Medicare Supplement Insurance (Medigap) actually does, why the letters matter, and how to avoid the mistakes that trip people up most often.

What Medigap actually does

Medigap works alongside Original Medicare (Part A and Part B). After Medicare pays its share of a covered service, your Medigap policy picks up some or all of what's left — things like the Part A hospital coinsurance, the Part B coinsurance, and the first three pints of blood.

It's important to know what Medigap is not. It is not Medicare Advantage (Part C). You cannot use both at the same time. Medigap also does not cover long-term care, dental, vision, hearing aids, or private-duty nursing.

Why the letters are standardized

In most states, Medigap plans are standardized by federal law. That means the benefits inside Plan G, Plan N, or any other letter are the same no matter which insurance company sells it. A Plan G in Madison covers the same core benefits as a Plan G sold anywhere else in Mississippi.

What can differ between companies is the price, the customer service, and whether the company offers extras like a fitness benefit. Because the coverage is identical letter-for-letter, comparing Medigap policies really comes down to premium and the insurer's reputation.

Two more things to know:

• Plans C and F are no longer sold to people who became eligible for Medicare on or after January 1, 2020. If you were eligible before that date, you may still be able to buy them.
• Plans K and L have lower premiums but higher out-of-pocket limits. Plan N has copays for some office and ER visits.

Drug coverage is separate

Medigap policies sold today do not include prescription drugs. If you want drug coverage, you'll enroll in a stand-alone Medicare Part D plan.

A few 2026 Part D facts worth keeping in mind:

• The Part D out-of-pocket cap is $2,100 for 2026.
• The Part D maximum deductible is $615.
• The old "donut hole" coverage gap is gone as of 2025 — Part D now has three phases.
• The Medicare Prescription Payment Plan lets you spread your drug costs over the year in monthly installments if that helps your budget.

The enrollment window that matters most

The single biggest Medigap mistake people make is missing their Medigap Open Enrollment Period. This is a one-time, six-month window that begins the month you're 65 or older and enrolled in Part B. During that window, insurance companies must sell you any Medigap policy they offer at the same price they'd charge a healthy person, regardless of your health history.

Outside that window, in most cases, insurers can use medical underwriting — meaning they can charge you more or turn you down based on health conditions. Mississippi does not have the broader year-round guaranteed-issue rules that a few states offer, so timing really matters here.

Medigap vs. Medicare Advantage — don't mix them up

Madison is in Madison County, where residents can choose between staying on Original Medicare (often paired with a Medigap and a Part D plan) or enrolling in a Medicare Advantage plan that bundles hospital, medical, and usually drug coverage together. Madison County has multiple Medicare Advantage plans and carriers available; the exact count changes each year during the Annual Enrollment Period.

Key differences to remember:

• You cannot have Medigap and Medicare Advantage at the same time.
• Medigap works with Original Medicare's nationwide network of providers who accept Medicare.
• Medicare Advantage plans typically use provider networks and may require referrals.

If you're weighing the two, think about how you use care, whether your doctors accept Medicare, and how much predictability you want in your monthly costs versus your at-the-doctor costs.

Dates to circle

• October 15 – December 7: Medicare Annual Enrollment Period (for Part D and Medicare Advantage changes).
• January 1 – March 31: Medicare Advantage Open Enrollment Period.
• Your Medigap Open Enrollment Period: The six months starting when you're 65 and enrolled in Part B.
• IRMAA note: Higher-income surcharges on Part B and Part D premiums begin above $109,000 in income for a single filer in 2026.