The best time for someone to buy a Medigap policy is during the 6-month Medigap open enrollment period. Because you can buy any Medigap policy sold in your state of residency, even if you suffer from health issues.
The 6-month period will automatically start the month you are 65 and enrolled in Medicare Part B, which is Medical coverage. After the enrollment period, enrollees may not be able to purchase a Medigap policy. If they are able to buy one, it will cost more.
During Open Enrollment
Medigap insurance companies are generally allowed to use medical underwriting to decide if they will accept an application and how much they will charge for a policy.
However, if someone applies during open enrollment, they can buy any Medigap policy a company sells, even if they suffer from health issues, for the same price as those in good health.
Outside of open enrollment
If someone applies for Medigap coverage after open enrollment ends, there is no guarantee that an insurance company will sell a Medigap policy if someone does not meet the medical underwriting requirements.
In some states, you have the option to buy another type of Medigap policy known as Medicare SELECT. If you purchase a Medicare SELECT plan, you have the right to change your mind within 12 months and have switched to a standard Medigap policy.