Medicare Supplement

Understanding Medigap Plan Letters A Through N

CHARLESTON, S.C. — If you've started shopping for a Medicare Supplement policy, you've probably run into a wall of letters: Plan A, Plan B, Plan G, Plan N, and more. It can feel like alphabet soup. The good news is that these letters are not random — they're a shorthand for a set of benefits that the federal government has standardized, so a Plan G sold by one company covers the same core things as a Plan G sold by another.

Here's a plain-English guide to what Medigap is, how the letters work, and where to turn for personal help in the Charleston area.

What a Medigap policy actually does

Medigap is short for Medicare Supplement Insurance. It's a private policy you can buy to help pay some of the out-of-pocket costs that Original Medicare (Part A and Part B) leaves behind — things like coinsurance, copayments, and, in some cases, the Part A deductible.

A few key points to keep in mind:

• Medigap works alongside Original Medicare, not with Medicare Advantage. If you're on a Medicare Advantage plan, you can't also use a Medigap policy.
• Medigap policies generally don't include prescription drug coverage. For drugs, most people pair Original Medicare and Medigap with a stand-alone Part D plan.
• You pay a monthly premium to the insurance company for Medigap, in addition to your Part B premium.

Why the letters exist

Before the 1990s, Medigap policies were a mess. Every insurer sold something different, and comparing plans was nearly impossible. Federal law now requires that Medigap policies be sold in standardized versions, each labeled with a letter.

In most states, including South Carolina, those letters run A, B, C, D, F, G, K, L, M, and N. (Massachusetts, Minnesota, and Wisconsin standardize their plans a bit differently.)

Here's the important part: the letter tells you what's covered, not who sells it. A Plan G from Insurer X and a Plan G from Insurer Y offer the same standardized benefits. The difference is the price, the customer service, and sometimes extras the insurer bundles on top.

What each letter generally covers

You can find the full official benefit chart at medicare.gov, but in broad strokes:

• Plans A and B cover the basics, like Part A hospital coinsurance and Part B coinsurance.
• Plans K, L, and M cover a share of certain costs rather than 100%, in exchange for lower premiums.
• Plan N covers most gaps but leaves you with small copays for some office and emergency visits.
• Plan G is one of the more comprehensive options available to newer enrollees.
• Plans C and F were more comprehensive still, but they are no longer sold to people who became eligible for Medicare on or after January 1, 2020. If you were eligible before that date, you may still be able to buy them.

Every Medigap plan of the same letter has the same core benefits nationwide — the price is what varies.

Timing matters: the Medigap Open Enrollment Period

The single most important thing to understand about Medigap is when you buy it.

Your Medigap Open Enrollment Period is a one-time, six-month window that starts the month you're 65 or older and enrolled in Part B. During this window, insurance companies must sell you any Medigap policy they offer at their best available rate, and they 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 — meaning they can ask health questions and potentially deny coverage or charge more. South Carolina follows the federal rules on this, so Charleston-area residents should pay close attention to that six-month window.

This is a separate deadline from Medicare's Annual Enrollment Period (Oct. 15 – Dec. 7) and the Medicare Advantage Open Enrollment Period (Jan. 1 – March 31), which apply to Advantage and Part D plans.

How Medigap fits with the rest of Medicare in 2026

Medigap doesn't cover prescriptions, but there are important 2026 changes on the drug side worth knowing if you're building a full coverage picture:

• Part D now has an annual out-of-pocket cap of $2,100 for covered drugs.
• The maximum Part D deductible is $615.
• The old "donut hole" coverage gap has been eliminated, replaced by a simpler three-phase structure.
• The Medicare Prescription Payment Plan lets you spread your drug costs across the year in monthly installments instead of paying big bills at the pharmacy counter.
• IRMAA — higher Part B and Part D premiums for higher earners — kicks in above $109,000 in income for a single filer in 2026.

Charleston is in Charleston County, where seniors have a wide range of Medicare Advantage and Part D options available. Medigap is a different route — one paired with Original Medicare — and comparing the two is worth doing carefully.