In 46 states, once you choose Medicare Advantage at 65, you can almost never leave. Of 65 million people enrolled in Medicare, 32 million are enrolled via Medicare Advantage. Medicare Advantage is a private alternative to Medicare.
The above article points out that should you choose to transition back to regular Medicare after being in Medicare Advantage you may face challenges in 46 states. The challenge is that in order to transition back to Medicare you will likely also need to also sign up for Medigap as Medicare alone requires more out of pocket payments than most retirees can afford. Hence those who sign up for Medicare invariably also require Medigap.
For many, Medicare Advantage may lose its advantage over time as it severely restricts options to choose your healthcare providers and facilities as well as other limitations. Those who choose Medicare Advantage and later want to switch back to regular Medicare + Medigap, risk being denied coverage by Medigap.
The problem arises as Medigap is allowed to conduct health screening and for those with preexisting conditions Medigap providers are permitted to deny coverage in 46 states (this is the one area post-Obamacare that still permits discrimination against those with pre-existing conditions). Hence, the cost advantage of Medicare Advantage may boomerang back on patients who want to switch back. New York, Connecticut, Maine, and Massachusetts are the 4 states that prevent Medigap underwriting.