Medicare Supplement

How Medigap's Standardized Letter Plans Actually Work

OWENSBORO, Ky. — If you've started reading about Medicare, you've probably run into a wall of letters: Plan A, Plan B, Plan G, Plan N, Plan K, Plan L. These are Medigap plans, also called Medicare Supplement Insurance. And the good news for anyone in Owensboro trying to sort this out is that the letters mean the same thing no matter which company sells them.

Here's a plain-English guide to what Medigap does, how the letters work, and the mistakes that catch people off guard.

What Medigap Actually Does

Medigap is extra insurance you can buy from a private company to help pay some of the costs that Original Medicare (Part A and Part B) leaves behind — things like coinsurance, copayments, and deductibles.

A few key points to keep straight:

• Medigap only works with Original Medicare. It does not work with Medicare Advantage.
• Medigap does not include prescription drug coverage. For drugs, you'd add a stand-alone Part D plan.
• You pay a monthly premium to the Medigap insurer, on top of your Part B premium.

Think of Medigap as a companion policy that fills in the gaps of Original Medicare. That's literally where the name comes from.

Why the Letters Exist

Before the 1990s, Medigap policies were a confusing mess. Two policies with the same name could cover totally different things. Congress stepped in and told insurance companies: if you're going to sell a Medigap plan, it has to follow a standard federal template.

Today, in most states (including Kentucky), Medigap plans come in 10 standardized versions, each labeled with a letter: A, B, C, D, F, G, K, L, M, and N.

That standardization is your friend. Plan G from Company X covers the same benefits as Plan G from Company Y. The price and customer service may differ, but the benefits inside the letter are identical by law. (Massachusetts, Minnesota, and Wisconsin do things a little differently, but Kentucky follows the standard letter system.)

What Each Letter Generally Covers

Every lettered plan covers a core set of benefits, like Part A hospital coinsurance. From there, each plan adds different pieces on top. For example:

• Some letters help with the Part B deductible.
• Some help with skilled nursing facility coinsurance.
• Some cover a share of foreign travel emergency care.
• Plans K and L are cost-sharing versions with lower premiums but yearly out-of-pocket limits.
• Plan N uses small copays for some office and ER visits.

An important rule from CMS: Plans C and F are no longer available to people who became eligible for Medicare on or after January 1, 2020. If you qualified before that date, you may still be able to buy or keep them. This trips up a lot of new enrollees who see Plan F recommended in older articles.

For the full official benefit chart, the best source is Medicare.gov's Medigap section — it lays out every letter side by side.

The Enrollment Window Most People Miss

This is where mistakes get expensive. There is a one-time Medigap Open Enrollment Period that lasts six months and starts the month you're both 65 or older and enrolled in Part B.

During that window:

• Insurance companies must sell you any Medigap plan they offer.
• They can't charge you more because of your health.
• They can't turn you down for pre-existing conditions.

After that six-month window closes, in most states you can still apply — but insurers can use medical underwriting. That means they can ask health questions, charge more, or say no. Kentucky generally follows federal rules here, so the six-month window really matters.

If you're thinking about switching from Medicare Advantage back to Original Medicare plus a Medigap plan later on, be aware that you may face underwriting at that point. That's a conversation worth having with a licensed advisor or your local SHIP counselor before you make a move.

How Medigap Fits With Everything Else in 2026

A few 2026 facts that connect to the bigger picture:

• Part D drug costs now have a $2,100 annual out-of-pocket cap, and the Part D maximum deductible is $615. Medigap does not touch drug costs, so a stand-alone Part D plan is still where drug protection comes from.
• The coverage gap ("donut hole") is gone as of 2025. Part D now has three phases instead of four.
• The Medicare Prescription Payment Plan lets you spread drug costs across the year in monthly amounts — separate from Medigap.
• IRMAA income-based surcharges start above $109,000 for a single filer in 2026, and apply to Part B and Part D premiums (not Medigap).

A Quick Note on Local Availability

Owensboro is in Daviess County, where — like the rest of Kentucky — the standardized federal letters apply. The number of insurance companies selling each letter can vary by ZIP code, and premiums for the same letter can differ from company to company. Medicare.gov's plan finder lets you look up which carriers offer which letters in Daviess County.