Medicare Supplement

Medicare Supplement plans in Boulder and the letter system

In Boulder, where retirees often piece together Medicare while juggling everything from mountain hikes to grandkid visits, one question comes up again and again: what exactly is a Medicare Supplement plan, and why are they labeled with letters?

Medicare Supplement insurance — usually called Medigap — is private insurance that helps pay some of the costs Original Medicare doesn't cover, like coinsurance, copayments, and certain deductibles. The letters (Plan A, B, D, G, K, L, M, N, and, for people who qualified before 2020, C and F) refer to standardized benefit packages. That standardization is the key to understanding how Medigap works.

What Medigap actually does

Original Medicare (Part A for hospital care and Part B for doctor visits and outpatient care) pays a big share of your medical bills — but not all of it. There's a Part A hospital deductible, a Part B deductible, and 20% coinsurance on most Part B services with no yearly out-of-pocket limit.

A Medigap policy steps in to help pay those gaps. Depending on the letter you choose, it may cover your Part A coinsurance, Part B coinsurance, the first three pints of blood, hospice coinsurance, skilled nursing coinsurance, and more.

Medigap does not cover prescription drugs. For that, you'd add a separate Part D drug plan.

Why the letters exist

Before Medigap plans were standardized, comparing policies was a nightmare. Today, federal rules require insurance companies to sell plans that fit into set benefit boxes labeled by letter.

That means Plan G from one company covers the exact same Medicare-related benefits as Plan G from another company. The differences come down to price, customer service, and extras a company may throw in (like gym benefits or hearing discounts).

So when you're comparing, you're really comparing two things:

• Which letter (benefit package) fits your needs?
• Which company offers the best price and service for that letter?

How Medigap fits with the rest of Medicare

Boulder is in Boulder County, where residents can generally choose between staying with Original Medicare (and optionally adding a Medigap policy and a Part D drug plan) or enrolling in a Medicare Advantage plan. You cannot have both a Medigap policy and a Medicare Advantage plan at the same time — Medigap is designed specifically to work alongside Original Medicare.

If you like the freedom to see any doctor or hospital in the country that accepts Medicare, Medigap paired with Original Medicare is often the route people consider. If you'd rather have an all-in-one plan with a network, that's the Medicare Advantage lane.

The enrollment window that matters most

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

During that window, insurance companies in Colorado must sell you any Medigap policy they offer at the best available rate, regardless of your health history. Miss it, and in most cases companies can use medical underwriting — meaning they can charge you more or deny coverage based on preexisting conditions. (A few limited "guaranteed issue" rights exist outside that window; the SHIP counselors below can walk you through them.)

This is different from the Annual Enrollment Period (October 15 – December 7) and the Medicare Advantage Open Enrollment Period (January 1 – March 31), which apply to Advantage and Part D plans, not Medigap.

A quick note on 2026 drug coverage

Because Medigap doesn't include drug coverage, most people pair it with a Part D plan. A few 2026 figures worth knowing:

• Part D out-of-pocket spending is capped at $2,100 for the year.
• The Part D maximum deductible is $615.
• The old coverage gap ("donut hole") is gone — Part D now has three phases.
• The Medicare Prescription Payment Plan lets you spread drug costs across monthly payments instead of paying at the pharmacy counter.
• IRMAA surcharges (extra amounts high earners pay for Part B and Part D) start above $109,000 in income for a single filer in 2026.

How to decide which letter is right for you

There's no single "right" Medigap letter — it depends on how you like to handle costs.

Some questions to think through:

• Do you want the most predictable bills, even if that means a higher monthly premium?
• Are you comfortable paying some cost-sharing (like a copay at the doctor) in exchange for a lower premium?
• Do you travel outside the U.S. often? Some letters include foreign travel emergency coverage.
• Were you eligible for Medicare before January 1, 2020? If so, you may still have access to plans that include the Part B deductible.

Prices for the same letter can vary a lot between companies, so it pays to shop around and to ask how the company sets rate increases over time.