Medicare Supplement

How Medigap's Letter Plans Work: A Plain-English Guide

THORNTON, Colo. — If you've started shopping for Medicare coverage, you've probably run into a wall of letters: Plan A, Plan B, Plan G, Plan N. These aren't the parts of Medicare. They're the names of Medicare Supplement plans — often called Medigap — and understanding how the letters work can take a lot of the mystery out of choosing coverage.

Here's a clear look at what Medigap does, why the letters exist, and how Thornton residents can find trustworthy help.

What Medigap actually does

Medigap is private insurance that works alongside Original Medicare (Part A and Part B). Original Medicare pays most of your hospital and doctor costs, but not all of them. You're still on the hook for things like the Part A hospital deductible, the Part B 20% coinsurance, and other out-of-pocket amounts that don't have a yearly cap.

A Medigap policy helps pay some of those leftover costs. It does not cover prescription drugs — for that, you'd add a separate Part D plan. And Medigap only works with Original Medicare; it doesn't pair with a Medicare Advantage plan.

Why the letters exist

Before the 1990s, Medigap policies were a confusing patchwork. Congress stepped in and told insurers: if you want to sell Medigap, you have to use standardized plans labeled with letters. That way, a Plan G sold by one company covers the same core benefits as a Plan G sold by another company.

Today, the plans sold to new enrollees include A, B, D, G, K, L, M, and N. (Plans C and F are still held by people who became eligible for Medicare before January 1, 2020, but they're no longer available to newly eligible beneficiaries.)

The benefits inside each letter are set by federal rules. What can differ between insurers is the price, the customer service, and sometimes small extras. That's why comparing quotes matters — the coverage under a given letter is the same, but the monthly premium isn't.

How the letters differ from each other

Each letter offers a different mix of coverage for things like:

• The Part A hospital deductible and coinsurance
• The Part B coinsurance or copayment
• The first three pints of blood
• Skilled nursing facility coinsurance
• Foreign travel emergency care (on some plans)

Some letters, like Plan G, cover nearly everything Original Medicare leaves behind except the Part B deductible. Others, like Plan K and Plan L, share costs with you up to a yearly out-of-pocket limit and usually come with lower premiums. Plan N sits in the middle, often with small copays for office and ER visits.

The right letter depends on how you use care, your budget, and how much predictability you want. A licensed agent or your local SHIP counselor can walk through the trade-offs without pushing a sale.

Enrollment timing matters — a lot

The best time to buy a Medigap policy is during your Medigap Open Enrollment Period — the six-month window that starts the month you're 65 and enrolled in Part B. During this window, insurers can't turn you down or charge you more because of health conditions.

Outside that window, in most states, insurers can use medical underwriting. That means your health history can affect whether you qualify and what you pay. Colorado has some additional protections, but the six-month window is still the safest time to enroll.

Medigap has its own timing rules — it is not tied to the Annual Enrollment Period (October 15–December 7) or the Medicare Advantage Open Enrollment Period (January 1–March 31). Those windows apply to Advantage and Part D plans.

What's available around Thornton

Thornton is in Adams County, where a range of insurance companies sell the standardized Medigap letter plans. Because the benefits inside each letter are federally set, your job as a shopper is mostly to compare premiums and company reputation for the same letter — not to compare benefit lists.

For a full picture of what's offered locally, Medicare's plan finder at medicare.gov lets you search Medigap policies by ZIP code.

A quick note on 2026 drug costs

Medigap doesn't cover prescriptions, but if you have Original Medicare plus a Medigap plan, you'll likely also carry a stand-alone Part D drug plan. A few 2026 figures worth knowing:

• The Part D out-of-pocket cap is $2,100 in 2026.
• The maximum Part D deductible is $615.
• The old "donut hole" coverage gap has been eliminated as of 2025.
• The Medicare Prescription Payment Plan lets you spread drug costs across the year in monthly installments instead of paying big amounts at the pharmacy counter.