Medicare Part D

How Medigap Fills the Gaps in Original Medicare, Denver

DENVER — If you're on Original Medicare (Part A and Part B), you already know it doesn't pay for everything. There are deductibles, coinsurance, and hospital costs that can add up in ways that are hard to predict. That's the gap Medicare Supplement insurance — better known as Medigap — is designed to fill.

Medigap, in plain English

Medigap is private insurance you buy on top of Original Medicare. It doesn't replace Medicare. It helps pay some of the out-of-pocket costs Medicare leaves behind, like the Part A hospital deductible, coinsurance days, and the 20% Part B coinsurance most people owe after meeting their deductible.

If you live in Denver, which sits inside Denver County, Medigap works the same way it does anywhere else in Colorado — the plans are standardized by the federal government, not by your ZIP code.

How the standardized letters work

Here's the part that trips people up: Medigap plans are sold by private insurance companies, but the benefits inside each lettered plan are set by federal rules. That means a Plan G from one company covers the same medical costs as a Plan G from another company. The premium can be different. The coverage cannot.

Today, the letters you'll see are:

• Plans A, B, D, G, K, L, M, and N — available to most people newly eligible for Medicare.
• Plans C and F — only available to people who were eligible for Medicare before January 1, 2020. If you became eligible after that date, these two are off the table.
• High-deductible versions of Plan G and Plan F — same benefits, but you pay a set deductible before coverage kicks in.

Plan G and Plan N are the two most people compare today. Plan G covers more; Plan N has some copays and doesn't cover the Part B excess charge. Neither is "better" — they're just different trade-offs between monthly premium and what you pay at the doctor.

What Medigap does not cover

This is where readers often get surprised. Medigap is medical-only. It does not include:

• Prescription drugs. For that, you need a separate Part D drug plan. The Part D annual out-of-pocket cap is $2,100 in 2026 and $2,400 in 2027. The maximum deductible is $615 in 2026 and $700 in 2027. The old "donut hole" coverage gap is gone — it was replaced in 2025 with a simpler three-phase design. There's also an optional Medicare Prescription Payment Plan that lets you spread drug costs across the year in monthly installments.
• Routine dental, vision, or hearing care.
• Long-term care, like an extended nursing home stay.
• Anything Medicare itself doesn't cover — Medigap only helps with what Medicare approves.

You also can't have Medigap and a Medicare Advantage plan at the same time. It's one or the other.

The enrollment window that matters most

The single most important date in Medigap is 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 in most states have to sell you any Medigap plan they offer at their best available rate, regardless of your health history.

Miss that window, and in most cases insurers can use medical underwriting. That means they can ask health questions, charge you more, or turn you down. Colorado has some additional protections in certain situations, but the six-month window is still the cleanest, simplest time to enroll.

This is different from Medicare's Annual Enrollment Period (October 15 – December 7) and the Medicare Advantage Open Enrollment Period (January 1 – March 31). Those windows are for Advantage and Part D — not Medigap.

How to decide if Medigap fits you

There's no universal right answer. A few honest questions to ask yourself:

• Do you travel or split time between states? Medigap works with any provider nationwide that accepts Medicare, which some retirees value.
• Do you prefer predictable monthly costs over lower premiums with more variable out-of-pocket costs? Medigap tends toward the former.
• Are you comfortable buying and managing a separate Part D drug plan? With Medigap, you'll need one.
• What's your budget, both today and ten years from now? Medigap premiums usually rise over time.
• Higher-income? Remember that IRMAA surcharges on Part B and Part D begin above $109,000 in income for a single filer in 2026. That affects Medicare premiums, not Medigap premiums, but it's part of the full picture.

If you're in Denver County and weighing your choices, a good next step is to price out a couple of lettered plans from different carriers and compare apples to apples — same letter, same benefits.