Medicare Supplement

Understanding the Standardized Medigap Plan Letters

SIMI VALLEY, Calif. — If you've ever tried to sort out Medicare Supplement coverage — often called Medigap — you've probably run into a puzzling alphabet: Plan A, Plan G, Plan N, and more. Those letters aren't random. They're a shorthand created to make comparing supplement policies simpler, and understanding them can save you a lot of second-guessing.

Here's a plain-English guide to what Medigap does, how the letters work, and where to turn for help in Ventura County.

What Medigap actually does

Original Medicare (Part A and Part B) covers a lot, but it doesn't cover everything. You're still responsible for deductibles, coinsurance, and copayments — and unlike most job-based insurance, Original Medicare has no annual out-of-pocket limit.

A Medigap policy is private insurance that helps pay some of those leftover costs. Depending on the plan letter you choose, it may cover things like the Part A hospital coinsurance, the Part B coinsurance, the first three pints of blood, hospice coinsurance, and skilled nursing facility coinsurance.

Medigap works only with Original Medicare. It does not work with Medicare Advantage, and it doesn't include prescription drug coverage — that comes from a separate Part D plan.

Why the letters exist

Before the early 1990s, supplement policies were a confusing mess. Two policies with the same name could cover very different things. To fix that, federal law standardized Medigap plans into lettered options. Today, in most states — including California — every Medigap policy sold with the same letter must offer the same core benefits, no matter which insurance company sells it.

That means Plan G from one carrier covers the same medical benefits as Plan G from another carrier. What can differ is the monthly premium, customer service, and extras like discount programs.

The current lineup of plans

In most states, the standardized plans available are A, B, C, D, F, G, K, L, M, and N. A few important notes from Medicare:

• Plans C and F are only available to people who were eligible for Medicare before January 1, 2020. If you became eligible on or after that date, these two are off the table.
• Plan G has become a popular choice for newer enrollees because it covers benefits similar to Plan F, minus the Part B deductible.
• Plans K and L have lower premiums but include cost-sharing and an out-of-pocket limit before full coverage kicks in.
• Plan N covers the Part B coinsurance but may leave you with small copays for some office and emergency room visits.

Massachusetts, Minnesota, and Wisconsin standardize their Medigap plans differently, so this letter system applies to the rest of the country, California included.

What's new — and what to keep an eye on

Medigap itself is fairly stable year to year, but the Medicare landscape around it keeps shifting. For 2026, a few program-level updates matter to anyone weighing supplement coverage alongside a Part D drug plan:

• The Part D out-of-pocket cap is $2,100 in 2026.
• The Part D deductible can be no more than $615.
• The coverage gap ("donut hole") was eliminated in 2025, leaving three simpler payment phases.
• The Medicare Prescription Payment Plan lets you spread drug costs across the year in monthly installments if you choose.
• IRMAA surcharges — extra premiums for higher-income enrollees — begin above $109,000 for a single filer in 2026.

None of these change how Medigap letters work, but they affect the total picture of what you'll pay across Medicare.

Simi Valley and Ventura County: where to look

Simi Valley is in Ventura County, where residents have access to Original Medicare plus Medigap, along with Medicare Advantage and stand-alone Part D drug plans. Medicare plan availability is set at the county level, so the specific insurers and Advantage options offered here are the same across Ventura County.

Your best window to buy a Medigap policy is your Medigap Open Enrollment Period — the six months that start when you're 65 or older and enrolled in Part B. During that window, insurers must sell you any Medigap plan they offer at the best available rate, regardless of your health history. Outside that window, in most cases, they can use medical underwriting.

Also worth knowing:

• Medicare Annual Enrollment Period: October 15 – December 7 (for Part D and Medicare Advantage changes).
• Medicare Advantage Open Enrollment Period: January 1 – March 31.

Medigap doesn't have a nationwide annual enrollment period, which is why the six-month window at 65 is so important.