Some things you should know about Medigap
You must have Medicare Part A and Part B.
If you have a Medicare Advantage plan, you can apply for a Medicare Supplement policy, but make sure you can leave the Medicare Advantage plan before your Medicare Supplement policy begins. The insurer can only sell you a Medicare Supplement plan if you are returning to Medicare Parts A and B.
You pay the private insurance company a monthly premium for the policy in addition to the monthly Part B premium that you pay to Medicare.
You can buy a policy from any insurance company that’s licensed in your state to sell one
Medicare Supplement policies are guaranteed renewable as long as you pay the premium and are truthful on your application.
When Can I buy a Medicare Supplement plan?
Open Enrollment period
The best time to buy a Medicare Supplement plan is during your Open Enrollment Period. This period lasts six months and begins the first day of the month in which you are 65 or older and enrolled in Medicare Part B.
So if you turn 65 on April 3 but don’t join Medicare B until May 25, your Medigap Open Enrollment Period will start on June 1, which is the first day of the month in which you are both 65 and enrolled in Part B.
Some states have additional Open Enrollment Periods including those for people under 65.