Medicare Supplement

The Medigap lettering system Merrimack Medicare buyers see

Merrimack, N.H. — If you've started shopping for a Medicare Supplement policy, you've probably noticed something strange: the plans are named with letters. Plan A, Plan G, Plan N, and a few others. It looks like alphabet soup, but there's a system behind it, and once you understand it, comparing policies gets a lot easier.

Medicare Supplement Insurance — often called Medigap — is private insurance that helps pay some of the costs Original Medicare (Part A and Part B) leaves behind, like coinsurance and deductibles. To make shopping fairer, the federal government standardized these plans by letter. That means Plan G from one company covers the exact same core benefits as Plan G from another company.

What Medigap actually does

Original Medicare covers a large share of hospital and doctor costs, but not all of it. You're still responsible for things like the Part A hospital deductible, the 20% Part B coinsurance, and certain other charges. A Medigap policy steps in to help cover some or all of those leftover costs, depending on which lettered plan you pick.

One important note: Medigap does not include prescription drug coverage. For that, most people add a stand-alone Part D plan. Medigap also does not work with Medicare Advantage. You choose one path or the other.

Why the letters exist

Before standardization, comparing supplement policies was confusing. Congress fixed that by requiring insurers to sell plans built from a common menu of benefits, each identified by a letter. Today, the plans available to most new enrollees include A, B, D, G, K, L, M, and N. Plans C and F are only available to people who were eligible for Medicare before January 1, 2020.

Because the benefits inside each letter are set by federal rules, the meaningful differences between two companies selling the same letter plan usually come down to price, customer service, and how the company handles rate increases over time.

What the letters generally cover

Every Medigap plan sold today covers Part A hospital coinsurance and an extra 365 days of hospital coverage after Medicare benefits end. From there, coverage varies:

• Some letters cover the Part B coinsurance in full; others require cost-sharing.
• Some cover the Part A deductible fully, partly, or not at all.
• A couple of letters (K and L) use an out-of-pocket limit and cover a percentage of costs until you hit it.
• Plan N generally covers Part B coinsurance but may leave small copays for office and emergency room visits.

Medicare.gov has a side-by-side chart that shows exactly which benefits each letter includes. It's the clearest way to see the differences at a glance.

When you can buy Medigap in New Hampshire

Merrimack is in Hillsborough County, and Medigap rules in New Hampshire follow federal standards along with some state-specific consumer protections. The single most important window is your Medigap Open Enrollment Period — the six months that begin the month you turn 65 and are enrolled in Part B. During that window, insurers must sell you any Medigap policy they offer at their best available rate, regardless of your health history.

Outside that window, insurers in most situations can use medical underwriting, which means they can charge you more or decline coverage based on health. There are limited "guaranteed issue" rights in certain circumstances — for example, if you lose other coverage — so it's worth asking before you assume you're locked out.

How this fits with the rest of Medicare

Even if you have a Medigap policy, you'll still want to think about drug coverage. In 2026, Part D has a $2,100 annual out-of-pocket cap on covered drugs and a maximum deductible of $615. The old "donut hole" coverage gap was eliminated in 2025, so Part D now runs in three phases. There's also an optional Medicare Prescription Payment Plan that lets you spread drug costs across the year in monthly installments.

Higher-income enrollees pay IRMAA surcharges on Part B and Part D; those start above $109,000 in income for a single filer in 2026.

Key dates to keep in mind: the Medicare Annual Enrollment Period runs October 15 through December 7, and the Medicare Advantage Open Enrollment Period runs January 1 through March 31. Note that Medigap has its own enrollment rules — it isn't tied to the fall AEP the way Part D and Medicare Advantage are.

Getting unbiased local help

Because Medigap decisions can affect your finances for years, it's worth talking with someone who isn't trying to sell you a policy. In New Hampshire, the State Health Insurance Assistance Program is called ServiceLink, and its counselors provide free, one-on-one Medicare guidance to Merrimack residents. You can also call 1-800-MEDICARE (1-800-633-4227) or visit medicare.gov to compare standardized benefits yourself.