Medicare Supplement

Medigap in Idaho Falls: how the letter plans fill gaps

IDAHO FALLS, Idaho — If you've ever opened a Medicare bill and wondered why you still owe money after Original Medicare paid its share, you're not alone. That's the gap Medicare Supplement insurance — often called Medigap — is designed to help fill.

Here in Idaho Falls, where many neighbors are aging into Medicare or helping a parent sort through the mail, Medigap is one of the most misunderstood pieces of the Medicare puzzle. Let's walk through what it does, what it doesn't do, and how those confusing letter names (Plan A, Plan G, Plan N and the rest) actually work.

What Medigap is — and what it isn't

Medigap is private insurance you can buy to work alongside Original Medicare (Part A and Part B). It helps pay some of the out-of-pocket costs Original Medicare leaves behind, like coinsurance, copayments, and, in some cases, deductibles.

A few important things Medigap is not:

• It is not part of Medicare Advantage. In fact, you can't have both at the same time.
• It is not a drug plan. Medigap policies sold today do not include Part D prescription drug coverage. You'd add a separate Part D plan for that.
• It is not a replacement for Medicare. You still need Part A and Part B, and you still pay your Part B premium.

Think of Medigap as a co-pilot to Original Medicare, not a substitute for it.

How the standardized letters work

This is where a lot of people get lost. In most states, including Idaho, Medigap plans are standardized by the federal government and labeled with letters: A, B, C, D, F, G, K, L, M, and N.

Here's the key idea: a Plan G from one company covers the exact same benefits as a Plan G from any other company. Same for Plan N, Plan K, and so on. The letter tells you what's covered. What differs between companies is the price, customer service, and how they handle rate increases over time.

A few notes worth knowing:

• Plans C and F are no longer available to people who became eligible for Medicare on or after January 1, 2020, because they cover the Part B deductible. If you were eligible before that date, you may still be able to buy them.
• Plans K and L have lower premiums but include an annual out-of-pocket limit and cover a smaller share of costs until you hit that limit.
• Plan N typically has lower premiums than Plan G but asks you to pay some copays at the doctor and emergency room.

You can compare the standardized benefit chart on Medicare.gov to see exactly what each letter covers.

When you can buy Medigap matters — a lot

The single most important date in Medigap is the start of your Medigap Open Enrollment Period. This is a six-month window that begins the month you're 65 and enrolled in Part B.

During this window, you have a guaranteed issue right. That means insurance companies can't turn you down or charge you more because of your health history. After this window closes, in most states, insurers can use medical underwriting — asking health questions and potentially denying coverage or charging more.

There are some other limited situations that give you guaranteed issue rights, such as losing certain other coverage. If you're unsure whether you qualify, call your State Health Insurance Assistance Program (SHIP) — Idaho's SHIP is called SHIBA — before you make any moves.

Idaho Falls is in Bonneville County — here's how availability works

Medigap and Medicare Advantage are two different tracks, and they're regulated differently.

Idaho Falls is in Bonneville County, where a range of Medicare Advantage and Part D plans are offered each year based on CMS's county-level plan lists. Medigap, on the other hand, is regulated more at the state level, and the specific plan letters available to you depend on which insurance companies are licensed to sell Medigap in Idaho.

If you want a full list of Medigap policies available in your ZIP code, the plan finder at Medicare.gov lets you search by location and see every carrier offering each lettered plan.

What Medigap doesn't cover

Even a comprehensive Medigap plan has limits. Medigap generally does not cover:

• Prescription drugs (you need a separate Part D plan)
• Routine dental, vision, or hearing care
• Long-term care (like a nursing home stay for custodial care)
• Hearing aids or eyeglasses

For 2026, Part D has its own set of rules worth remembering: the out-of-pocket cap on covered drugs is $2,100, the maximum Part D deductible is $615, and the old coverage gap — the "donut hole" — has been eliminated as of 2025. There's also an optional Medicare Prescription Payment Plan that lets you spread your drug costs into monthly payments across the year.

Key dates to keep on the fridge

• Medigap Open Enrollment: six months starting when you're 65 and enrolled in Part B.
• Medicare Annual Enrollment Period: October 15 – December 7 (this is for Part D and Medicare Advantage — not Medigap).
• Medicare Advantage Open Enrollment: January 1 – March 31.

Also worth knowing: if your income is above $109,000 as a single filer in 2026, IRMAA surcharges may increase what you pay for Part B and Part D.