Medicare Part D
Medigap in Chicago: how the letter plans fit together
CHICAGO — If you've spent any time comparing Medicare choices, you've probably run into the word "Medigap" — and just as quickly wondered what it actually does. With the Medicare Annual Enrollment Period running Oct. 15 through Dec. 7, this is the season a lot of Chicagoans finally sit down and try to sort it out. Here's a plain-English look at how Medicare Supplement insurance works, and how those standardized letter plans fit together.
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Key takeaways
- Medigap is a private policy that works alongside Original Medicare to help cover leftover costs like coinsurance, copayments, and sometimes deductibles, but it does not replace Original Medicare or add extra benefits like dental or vision.
- In most states, including Illinois, Medigap plans are standardized and labeled by letters (A, B, C, D, F, G, K, L, M, and N), so the same lettered plan offers the same core benefits no matter which company sells it, meaning price and customer service are usually what differ.
- Your one-time, six-month Medigap Open Enrollment Period starts the month you turn 65 or older and enroll in Part B, and during that window insurers must accept you and can't charge more based on your health, while outside that window medical underwriting may apply in most states.
- Medigap does not include drug coverage, so most people pairing it with Original Medicare also get a separate Part D plan, and Star Ratings you'll see this time of year apply only to Medicare Advantage and Part D plans, not to Medigap.
What Medigap is — and what it isn't
Medicare Supplement insurance, usually called Medigap, is a private policy that works alongside Original Medicare (Part A and Part B). It's designed to help pay some of the out-of-pocket costs Original Medicare leaves behind — things like coinsurance, copayments, and, in some cases, deductibles.
A few key things to know:
- Medigap only works with Original Medicare. It does not work with Medicare Advantage.
- Medigap does not include prescription drug coverage. For that, you'd add a separate Part D plan.
- Medigap does not cover long-term care, most dental, vision, hearing aids, or private-duty nursing.
In short: Medigap fills in gaps in Original Medicare. It doesn't replace it, and it doesn't add new benefits like dental cleanings or eyeglasses.
How the standardized letter plans work
In most states, including Illinois, Medigap policies are standardized by the federal government and labeled with letters — Plan A, B, C, D, F, G, K, L, M, and N. (Plans E, H, I, and J are no longer sold.)
Standardization means the benefits inside each lettered plan are the same from one insurance company to another. A Plan G from one carrier covers the same core things as a Plan G from another carrier. What can differ is the price and the company's customer service.
Two important notes for newer enrollees:
- Plans C and F, which cover the Part B deductible, are only available to people who became eligible for Medicare before Jan. 1, 2020.
- Plans K and L have lower premiums but higher out-of-pocket shares.
Because the benefits are standardized, comparing Medigap really comes down to comparing price, the company behind the policy, and how each insurer handles rate increases over time.
When you can buy a Medigap policy
Timing matters more with Medigap than most people realize.
Your Medigap Open Enrollment Period is a one-time, six-month window that starts the month you're 65 or older and enrolled in Part B. During that window, you have a "guaranteed issue" right — insurers can't turn you down or charge you more because of your health.
Outside that window, in most states insurers can use medical underwriting, which can affect whether you're accepted and what you pay. Illinois has some additional protections in certain situations, but the safest bet is to know your open enrollment dates and plan around them.
If you're weighing a switch between Medicare Advantage and Original Medicare with a Medigap policy, keep the calendar in mind: the Medicare Advantage Open Enrollment Period runs Jan. 1 through March 31 each year, and the Annual Enrollment Period runs Oct. 15 through Dec. 7.
How Medigap fits with Part D and 2027 drug costs
Because Medigap doesn't include drug coverage, most people who choose Original Medicare plus Medigap also enroll in a stand-alone Part D plan.
A few program-level Part D facts for 2027 worth knowing:
- The Part D out-of-pocket cap is $2,100 in 2026. Once your covered drug costs reach that amount, you pay $0 for covered drugs the rest of the year.
- The Part D maximum deductible is $615 in 2026.
- The old coverage gap, or "donut hole," was eliminated in 2025. Part D now has three phases instead of four.
- The Medicare Prescription Payment Plan lets you spread your drug costs across the calendar year in monthly payments instead of paying at the pharmacy counter.
- IRMAA surcharges for higher-income beneficiaries begin above $109,000 in income for a single filer in 2026.
None of these figures change based on which Medigap plan you pick — they apply program-wide.
What this looks like in Chicago
Chicago is in Cook County, where Medicare beneficiaries generally have access to a wide range of stand-alone Part D plans and multiple insurance companies offering Medigap policies. Medigap availability isn't tied to your ZIP code the way Medicare Advantage is — but the insurers doing business in Illinois, and the prices they file, are regulated at the state level through the Illinois Department of Insurance.
For personalized help comparing what's available in Cook County, the state's SHIP program (in Illinois it's called the Senior Health Insurance Program) offers free, unbiased counseling.
A quick word on Star Ratings
You'll see Star Ratings talked about a lot this time of year. Those ratings apply to Medicare Advantage and Part D plans — not Medigap. They measure things like customer service, member complaints, and, for drug plans, pricing accuracy and safety. They're a useful data point, not a recommendation, and they don't tell you whether a plan fits your specific doctors, drugs, or budget.
By the numbers
Medicare Part B premium, 2006–2026
The standard monthly Part B premium has climbed from $88.50 in 2006 to $202.90 in 2026. Hover any point for that year’s premium.
Source: CMS. Standard premium shown; in some hold-harmless years many existing enrollees paid less. Confirm at Medicare.gov.
By the numbers
How people get Medicare in Cook County
(MA penetration in Cook County)
MA penetration from CMS enrollment data; Medigap share is an estimate. U.S. average is about 54% Medicare Advantage. These are area-level figures, not plan-specific.
Try it
How the 2026 Part D drug cap works
Slide to your estimated yearly prescription costs and see how the new $2,100 out-of-pocket cap protects you. This illustrates the standard Part D benefit; your plan may structure costs differently.
Once your out-of-pocket spending on covered drugs reaches $2,100, you pay nothing more for the rest of 2026. Confirm details at Medicare.gov.
Explore
When can you enroll? An interactive year
Enrollment windows are federal and the same nationwide. Confirm your personal dates at Medicare.gov or 1-800-MEDICARE.
Good to know
Frequently asked questions
Do I need a Medigap policy if I already have Medicare Advantage?
Does Medigap cover dental, vision, or hearing?
If I move within Illinois — or out of state — does my Medigap policy travel with me?
- CMS — Medicare Part D program rules (medicare.gov)
For personalized answers, contact Medicare.gov, 1-800-MEDICARE, or your local SHIP.