Medicare Supplement

Medigap, explained: what those plan letters mean

# Medicare Supplement insurance, explained: what Medigap does and doesn't…

ARVADA, Colo. — If you have Original Medicare and worry about the bills it doesn't fully pay, you've probably heard about Medicare Supplement insurance — also called Medigap. These plans are sold by private insurance companies, but the benefits inside each lettered plan are set by federal rules. That standardization is what makes Medigap easier to compare than most insurance you'll shop for.

Here in Arvada, Medigap works the same way it does across Colorado and most of the country. What changes from company to company is the price and the customer service — not the core benefits inside a given letter.

What Medigap actually does

Original Medicare (Part A and Part B) pays a big share of your hospital and doctor bills, but not all of it. You're still responsible for things like the Part A hospital deductible, Part B coinsurance (usually 20% after the deductible), and certain other costs. There's also no yearly out-of-pocket limit on Original Medicare by itself.

Medigap fills in some of those gaps. Depending on the letter you choose, it can cover coinsurance, copayments, deductibles, and — in a few plans — care while traveling outside the U.S.

Medigap only works alongside Original Medicare. It does not work with a Medicare Advantage plan. You either have Advantage, or you have Original Medicare (usually with Medigap and a Part D drug plan).

How the standardized letters work

In most states, including Colorado, Medigap plans are sold under 10 standardized letters: A, B, C, D, F, G, K, L, M, and N. Two things to know:

• The benefits inside each letter are set by federal rules. A Plan G from one company covers the same core benefits as a Plan G from another.
• Plans C and F are only available to people who became eligible for Medicare before January 1, 2020. If you turned 65 after that, you can't buy them new.

Plans K and L are cost-sharing plans, meaning they pay a percentage of certain costs and include a yearly out-of-pocket limit. Plan N generally has lower premiums but asks you to pay small copays for some office and emergency room visits.

Because the benefits are standardized, the smartest comparison is usually price and the insurer's reputation for service and rate stability — not the benefit list itself.

What Medigap doesn't cover

Medigap is not a full replacement for other coverage. It generally does not cover:

• Prescription drugs (you'll want a separate Part D plan)
• Routine dental, vision, or hearing care
• Long-term care (custodial care in a nursing home)
• Hearing aids, eyeglasses, or private-duty nursing

For prescriptions, remember the 2026 Part D rules: a maximum deductible of $615, a new $2,100 annual out-of-pocket cap on covered drugs, and the option to spread your drug costs across the year through the Medicare Prescription Payment Plan.

Timing matters: the Medigap Open Enrollment Period

The best time to buy a Medigap policy is during your Medigap Open Enrollment Period — a one-time, six-month window that begins the month you're 65 or older AND enrolled in Part B. During that window, companies can't turn you down or charge you more because of your health.

Miss that window, and in most states insurers can use medical underwriting to decide whether to sell you a policy and at what price. Colorado has some additional protections in certain situations, but the six-month window is still your strongest guarantee.

Note that this is different from Medicare's Annual Enrollment Period (Oct. 15 – Dec. 7) and the Medicare Advantage Open Enrollment Period (Jan. 1 – March 31). Those windows apply to Advantage and Part D — not Medigap.

A quick local note

Arvada sits mostly in Jefferson County, with parts in Adams County. Medicare Advantage and Part D plan availability is set at the county level, so what's offered in Arvada matches what's offered across Jefferson County. Medigap is different: because the letter plans are standardized federally, an Arvada resident has the same benefit choices as someone in almost any other Colorado ZIP code — the differences come down to which insurers are licensed here and how they price each plan.

Where to get unbiased help

Before you buy, it's worth talking to someone who doesn't earn a commission on the sale. Colorado's State Health Insurance Assistance Program (SHIP) offers free, one-on-one counseling for Medicare questions, including Medigap comparisons. You can also use Medicare's own Medigap tool to see which plans are sold in your ZIP code.