Medicare Supplement

Understanding Medigap: What Each Plan Letter Really Means

CHATTANOOGA, Tenn. — If you're new to Medicare, the alphabet soup of "Plan G," "Plan N," and "Plan K" can feel confusing. These letters refer to Medicare Supplement Insurance, often called Medigap — a type of private policy designed to help pay some of the out-of-pocket costs that Original Medicare leaves behind.

Chattanooga readers ask: what does Medigap actually cover?

Here in Chattanooga, which sits in Hamilton County, many people on Original Medicare pair their coverage with a Medigap policy. Understanding what those letters mean is the first step to making a confident choice.

What Medigap does — and what it doesn't

Medigap works alongside Original Medicare (Part A and Part B). After Medicare pays its share of a covered service, your Medigap policy can help cover some of what's left — things like coinsurance, copayments, and, for some plans, the Part A deductible.

A few important points from Medicare.gov:

• Medigap only works with Original Medicare. If you're enrolled in a Medicare Advantage plan, you generally can't use a Medigap policy.
• Medigap policies are sold by private insurance companies, but the benefits within each lettered plan are set by federal and state law.
• Most Medigap plans do not include prescription drug coverage. For that, you'd typically add a separate Part D plan.
• Medigap doesn't cover things like long-term care, dental, vision, hearing aids, or private-duty nursing.

Why the plans use letters

To keep shopping simpler, Medigap policies are standardized. That means a Plan G sold by one company covers the same core benefits as a Plan G sold by another company. The price can differ, but the benefits inside that letter do not.

In most states, including Tennessee, Medigap plans are labeled A, B, C, D, F, G, K, L, M, and N. (Plans C and F are generally only available to people who became eligible for Medicare before January 1, 2020.) Massachusetts, Minnesota, and Wisconsin standardize their plans a little differently.

Each letter represents a specific mix of benefits. For example:

• Some letters cover the Part A hospital coinsurance and hospice cost-sharing.
• Some help with the Part B coinsurance.
• Some cover the first three pints of blood, or skilled nursing facility coinsurance.
• A couple of letters (K and L) use an out-of-pocket yearly limit and cover a percentage of certain costs rather than the full amount.

Because the benefits are fixed by law, comparing Medigap plans usually comes down to price, the company's customer service, and rate stability over time.

When you can buy a Medigap policy

The best window to buy a Medigap policy is your Medigap Open Enrollment Period — the six-month stretch that begins the month you're 65 or older and enrolled in Part B. During this window, insurance companies can't turn you down or charge you more because of your health history.

Outside that window, in most states, insurers can use medical underwriting. That means your health could affect whether you're accepted or what you pay. A few states have extra protections, so it's worth asking about your specific situation.

How Medigap fits with the rest of Medicare in 2026

Medigap doesn't replace the other parts of Medicare — it works with them. A few 2026 facts worth knowing:

• Part D (drug coverage) has a $2,100 annual out-of-pocket cap in 2026, and the maximum deductible is $615.
• The old coverage gap ("donut hole") was eliminated in 2025, so Part D now has three phases.
• The Medicare Prescription Payment Plan lets you spread your drug costs across the year in monthly payments if that helps your budget.
• IRMAA surcharges on Part B and Part D begin above $109,000 in income for a single filer in 2026.
• Annual Enrollment runs October 15 – December 7, and Medicare Advantage Open Enrollment runs January 1 – March 31. These windows are for Advantage and Part D changes — Medigap has its own rules.