Medicare Supplement

How Medigap's A-Through-N Letters Work, Explained Simply

# How Medigap's A-Through-N Letters Work, Explained…

KIRKWOOD, Mo. — If you've started shopping for a Medicare Supplement policy, you've probably noticed something unusual: the plans are labeled with letters. Plan A. Plan G. Plan N. And you may have wondered why one insurer's Plan G looks a lot like another's. That's not a coincidence. It's how Medigap is built.

Medigap plans are standardized by federal law. That means the letters aren't marketing — they're a promise about what's inside the policy.

What Medigap actually does

Medigap — also called Medicare Supplement Insurance — is a private policy that helps pay some of the out-of-pocket costs Original Medicare (Part A and Part B) leaves behind. That includes things like coinsurance, copayments, and, in some plans, the Part A deductible.

Here's the important part: Medigap only works with Original Medicare. If you're enrolled in a Medicare Advantage plan, you can't use a Medigap policy alongside it. You also need to have both Part A and Part B to buy Medigap, and you pay a separate monthly premium for it in addition to your Part B premium.

Medigap does not include prescription drug coverage. For drugs, you'd add a stand-alone Part D plan.

Why the letters exist

Back in the early 1990s, Congress standardized Medigap policies to make shopping easier. Before that, insurers could design their own supplement plans however they liked, and comparing them was nearly impossible.

Today, in most states, a Plan G from one company must offer the exact same core benefits as a Plan G from any other company. The price and customer service can differ. The benefits inside a given letter cannot.

That's why the letters matter. Once you understand what a letter covers, you can focus on comparing price, the insurer's reputation, and whether the premium is likely to stay stable over time.

What the letters cover, in plain terms

There are ten standardized letters currently recognized: A, B, C, D, F, G, K, L, M, and N. Each letter is a different bundle of benefits.

• Plan A covers the most basic set of benefits and is offered by every Medigap insurer.
• Plans B, D, G, M, and N add more coverage in different combinations, such as help with the Part A deductible or skilled nursing coinsurance.
• Plans K and L have lower premiums but require you to pay a share of costs until you hit an annual out-of-pocket limit.
• Plans C and F are only available to people who were eligible for Medicare before January 1, 2020. If you became eligible on or after that date, these two are off the table for you.

Massachusetts, Minnesota, and Wisconsin standardize their Medigap plans differently — but for Kirkwood residents, the letter system above applies.

The Kirkwood picture

Kirkwood is in St. Louis County, where residents shopping for a Medigap policy can generally choose from multiple insurance carriers licensed to sell these standardized plans in Missouri. Because the benefits inside each letter are set by federal rules, the real comparison work is on price, the company's track record, and how premiums may rise over time.

Missouri also has its own consumer protections and enrollment windows that can affect what plans you qualify for and at what price. Timing matters: the best window to buy a Medigap policy is usually your six-month Medigap Open Enrollment Period, which starts the month you're 65 or older and enrolled in Part B. During that window, insurers cannot turn you down or charge you more because of your health.

A quick note on drug coverage and 2026 costs

Medigap doesn't cover prescriptions, so most people pair it with a stand-alone Part D drug plan. A few 2026 figures worth knowing:

• Part D will have a $2,100 annual cap on what you pay out of pocket for covered drugs.
• The Part D deductible is capped at $615 for 2026.
• The old "donut hole" coverage gap is gone as of 2025 — Part D now has three phases instead of four.
• A Medicare Prescription Payment Plan lets you spread drug costs across the year in monthly installments if you choose.