When you're 65 and first enrolling in Medicare, Medicare Advantage plans feel like an obvious choice. No monthly premium, simpler coverage, and if it doesn't work out, you can always switch back to Original Medicare, right? That's where many people discover a costly surprise.
A 71-year-old woman in Florida learned this the hard way. After two years of fighting her Advantage plan over a cardiology referral, she decided to leave. She wanted to return to Original Medicare and add Medigap Plan G, which covers most of the gaps in Original Medicare's cost-sharing. The problem? When the insurer reviewed her 2023 stent placement, they denied her application. Other carriers did the same.
The trap lies in timing. When you first enroll in Part B (the medical insurance portion of Medicare), you have a six-month window where any Medigap insurer must sell you coverage without reviewing your health history. This is called the Medigap open enrollment period. Inside those six months, carriers cannot deny you or charge extra because of pre-existing conditions, though they can adjust premiums based on age, location, and tobacco use.
Once that window closes, the rules flip. Outside the enrollment period, most insurers can review your medical records, prescription history, and recent hospitalizations. A stent, active cancer treatment, insulin use, or other health factors can lead to denial or higher rates depending on your state and which carrier you approach. The diagnosis matters, the timing matters, and which insurance company you choose matters.
There are some federal protections beyond that initial six-month window. If you joined Advantage as your first Medicare choice at 65, you have a 12-month trial period to return to Original Medicare and buy Medigap without underwriting. If you dropped Medigap to try Advantage for the first time, that right applies too. Guaranteed-issue rights also exist if your plan terminates, leaves your service area, or makes major network changes. But these protections don't help someone who voluntarily leaves Advantage after a few years without triggering one of these events.
State rules add another layer. New York and Connecticut offer continuous Medigap protections. Massachusetts has an annual open-enrollment period. Maine provides an annual guaranteed-issue option for Plan A. Other states have birthday or anniversary-based rules. Before assuming your door is open or closed, check your specific state's regulations.
Original Medicare without Medigap is expensive. Part A charges a $1,736 inpatient deductible per benefit period plus coinsurance for hospital stays. Part B has a $202.90 monthly premium, a $283 annual deductible, and you pay 20 percent coinsurance on most services, with no annual out-of-pocket cap. A cancer diagnosis or major surgery can quickly become financially devastating. Medigap Plan G closes most of these holes.
If you're considering switching from Advantage, act strategically. Apply for Medigap before leaving Advantage—don't rely on informal pre-screening. Get written acceptance in writing and coordinate effective dates carefully. During the Medicare Advantage Open Enrollment Period (January 1 through March 31), you can switch between Advantage plans or return to Original Medicare, but returning to Original Medicare doesn't guarantee Medigap acceptance. Finally, verify every possible guaranteed-issue right before submitting to underwriting. Keep all notices and coverage letters that could prove eligibility.
The Advantage decision at 65 doesn't have to be permanent, but the exit can narrow significantly once health issues appear. Understanding these rules now, while you're still in the six-month window, is what keeps a frustrating plan from becoming a coverage mistake.