5. What is a Medigap policy? Posted on September 11, 2017 at 12:17 pm.Written by advantage_admin Medigap policies are sold by private insurance companies. They can help cover deficiencies in Original Medicare, such as copays, coinsurances, and deductibles. You will generally have to pay a monthly premium while also paying for Part B. They only cover one person. You must have Medicare Parts A and B. You may not have a Medicare Advantage plan and a Medigap policy at the same time. Post navigation 4. What is Medicare Secondary Payer?6. How can I switch from a traditional Medicare plan to a Medicare Advantage plan?