Medicare Supplement

How Medigap's Lettered Plans Work — and Why It Matters

SILVER SPRING, Md. — If you've ever tried to compare Medicare Supplement plans, you've probably run into a wall of letters: Plan A, Plan G, Plan N, and more. It can feel like alphabet soup. The good news? Those letters aren't random. They're part of a system designed to make shopping easier and fairer for people on Original Medicare.

Here's a plain-English guide to what Medigap does, how the standardized letters work, and the small mistakes that can cost people later.

What Medigap actually does

Medigap — also called Medicare Supplement Insurance — is a private policy 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 Medicare leaves behind, like coinsurance, copayments, and certain deductibles.

A few important points from Medicare.gov:

• Medigap only works with Original Medicare. It does not work with Medicare Advantage.
• You must already have Part A and Part B to buy a Medigap policy.
• Medigap policies generally do not include prescription drug coverage. For drug coverage, you'd add a stand-alone Part D plan.
• Each Medigap policy covers one person. Spouses need their own policies.

Why the letters exist

Before the system was standardized, comparing supplement policies was nearly impossible. Two plans with the same name could cover very different things. To fix that, federal law now requires most Medigap plans to be standardized — meaning a Plan G sold by one company covers the exact same benefits as a Plan G sold by another company.

The letters currently offered to new enrollees include A, B, D, G, K, L, M, and N. (Plans C and F are still available, but generally only to people who became eligible for Medicare before January 1, 2020.) Massachusetts, Minnesota, and Wisconsin use their own standardization systems.

Because the benefits inside each letter are set by law, the main things that can differ between carriers are:

• Price (premiums can vary a lot)
• Customer service and reputation
• Optional extras some companies add on

That's why it's worth comparing carriers even when the plan letter is the same.

How the letters differ from each other

Each letter is a different "package" of benefits. Some cover almost everything Medicare doesn't. Others cover less but come with lower premiums. A few, like Plans K and L, use cost-sharing with an annual out-of-pocket limit.

Rather than memorize each one, Medicare.gov offers a side-by-side chart showing exactly what each letter covers. That's the safest place to compare, because it's updated directly by CMS.

Silver Spring is in Montgomery County, where residents have access to a range of Medigap carriers as well as Original Medicare and Medicare Advantage options. Medigap availability is set at the state level, so Maryland residents generally see the same lettered plans offered — though pricing and carrier choices differ.

The mistake people make most often: missing the open enrollment window

This is the piece that trips up the most people, so read carefully.

You get a one-time, six-month Medigap Open Enrollment Period that starts the month you're both 65 or older and enrolled in Part B. During that window:

• Insurers cannot turn you down for health reasons.
• They cannot charge you more because of pre-existing conditions.
• You can pick any Medigap plan sold in your state.

After that window closes, insurers in most states can use medical underwriting — meaning they can ask about your health, charge more, or deny coverage entirely. Some states have extra protections, but Maryland's rules follow the federal baseline for most situations.

If you're thinking about Medigap, the six-month window is the safest time to enroll. Waiting can limit your choices later.

Medigap vs. Medicare Advantage — a common mix-up

Medigap and Medicare Advantage are not the same, and you can't have both at the same time.

• Medigap works with Original Medicare and helps pay Medicare's leftover costs.
• Medicare Advantage (Part C) replaces Original Medicare with a private plan that often bundles medical and drug coverage.

Switching between them is possible but comes with rules — and, in many cases, medical underwriting if you're moving into Medigap after your initial window. This is where a call to your State Health Insurance Assistance Program (SHIP) can save a lot of confusion.

A quick note on 2026 costs (for the drug side)

Medigap itself doesn't cover prescriptions, but most people pair it with a Part D plan. For 2026, a few program-level figures worth knowing:

• Part D out-of-pocket cap: $2,100
• Part D maximum deductible: $615
• The old coverage gap ("donut hole") is gone as of 2025.
• The Medicare Prescription Payment Plan lets you spread drug costs across the year in monthly payments.
• IRMAA surcharges start above $109,000 in income for a single filer in 2026.