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Oklahoma’s Two Medicare Calendars: AEP and the Medigap Birthday Rule

Oklahoma has two Medicare calendars: Annual Enrollment (Oct. 15–Dec. 7) for Advantage and Part D, and a 60-day Medigap birthday window. Here is how to use both without mixing them up.

A Medicare agent reviews coverage documents at a kitchen table with an older couple, papers and coffee cups on the table and a wall calendar behind them.
A yearly Medicare review in an Oklahoma kitchen. Bring the papers. Ask about Annual Enrollment and your Medigap birthday window before either one closes.

October 15 is not the only date that matters if you have Medicare in Oklahoma. Annual Enrollment runs October 15 through December 7. That is when you can join, switch, or drop a Medicare Advantage plan or a Part D drug plan, with the new coverage starting January 1. Medigap, the supplement that sits on top of Original Medicare, does not use that window. Oklahoma built a second calendar around your birthday.

Since September 2023, Oklahoma Medigap policyholders who have not had more than a 90-day gap in coverage get a guaranteed-issue chance each year to move to another Medigap plan with equal or lesser benefits. Carriers meet the rule with a 60-day window that starts 30 days before your birthday and ends 30 days after. No health questions. No medical exam. You cannot use that window to jump to a richer letter plan, and it does not apply to Medicare Advantage. Mix those two calendars up and you either miss a cheaper supplement or you try to change an Advantage plan on your birthday and get told no.

Advantage and Medigap solve different problems. Advantage plans in Oklahoma often advertise $0 premiums, dental extras, and a network. In Oklahoma County alone, 2026 shoppers faced dozens of Advantage options, many at $0 premium, with maximum out-of-pocket limits that still run into the thousands. Medigap costs more each month and does not include Part D, but it lets you see any doctor who takes Original Medicare. If you like your specialists in Oklahoma City, Tulsa, or Norman and you travel, that difference is the whole decision. Plans also change every year. Blue Cross and Blue Shield of Oklahoma ended some 2025 Advantage contracts and mapped members into new 2026 plans. A $0 premium last fall is not a promise for next fall.

That is why a yearly review is not optional. OK Medicare Help puts it simply: “Your healthcare needs change over time, and so do Medicare plans.” Walk in with your drug list, your doctors, and last year’s Explanation of Benefits. Ask whether your Part D formulary still covers your prescriptions, whether your hospital is in-network, and whether a Medigap birthday switch would cut the premium without cutting the letter benefits you already have. Local shops on the Best Oklahoma Medicare Agents list, including Sooner State Advisors, Boomer Medicare Help, Navigating Medicare, and Oklahoma Health Options, LLC, do this work at no cost to you. The commission comes from the carrier, not from your checking account.

Prescription bottles lined up on a living-room coffee table next to printed benefit forms and a red pen.

Start the review with what you actually take. A current drug list and last year’s paperwork tell you whether your Part D plan still fits.

Do not skip the free public option either. The Oklahoma Insurance Department’s Senior Health Insurance Counseling Program (SHIP) will compare Advantage, Part D, and Medigap side by side without selling a policy. Call 1-800-763-2828 or 405-521-2828. If income is tight, ask OHCA about QMB, SLMB, and QI through SoonerCare. Those programs can pay the Part B premium, which is $202.90 a month in 2026, and in some cases the deductibles and copays.

Mark two dates on the same refrigerator calendar. Circle October 15 through December 7 if you have Advantage or Part D. Circle the 60 days around your birthday if you have Medigap. Then use the Best Oklahoma Medicare Agents list at best-medicare-agent-oklahoma.com to pick a local, licensed agent who already works these two calendars. Compare the Top 10 profiles, call the office that fits your county and your plan type, and do it before the window opens, not on the last afternoon. The plan that fit at 65 is not automatically the plan that fits at 72.

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