The single best time to buy a Medicare Supplement plan is during your Medigap Open Enrollment Period. This is a one-time, six-month window that starts the month you turn 65 and are enrolled in Medicare Part B.
During this period, insurance companies cannot deny you coverage for any reason. They cannot charge you more because of pre-existing conditions. They cannot make you wait for coverage to begin. This is federal law, and it applies in every state.
After your Open Enrollment Period ends, insurance companies in most states can use medical underwriting to decide whether to sell you a policy and how much to charge. If you've developed health conditions since turning 65, you could face significantly higher premiums or be denied coverage altogether.
A small number of states — including California, Connecticut, Massachusetts, Missouri, and New York — have additional protections that guarantee access to Medigap plans year-round. But even in these states, pricing may be higher outside of your initial enrollment window.
There are specific circumstances where federal law gives you a guaranteed right to buy a Medigap plan regardless of your health. These include losing employer group coverage, having a Medicare Advantage plan leave your area, or being enrolled in a Medicare Advantage plan for less than 12 months and wanting to switch back to Original Medicare.
The earlier you enroll, the lower your rates will be — and the fewer questions you'll have to answer about your health. If you're within six months of turning 65, comparing plans now is the most important financial decision you can make for your healthcare costs in retirement.