You’re first eligible for a Medicare supplement plan — also known as “Medigap” — the first month you have Medicare Part B and are age 65 or older. CMS says this is the best time to purchase a Medigap policy, as you generally get better prices and more choices among policies.
During this six-month window, you can purchase any Medigap policy sold in your state. That is true even if you have health issues. Crucially, you may not be able to purchase a Medigap policy after this enrollment period elapses if you have health problems. Or, you may pay more for this coverage.
Medigap plans are only for people with Medicare Parts A and B. Medicare Advantage plan members can’t buy Medicare supplement plans.