What Does Medigap Insurance Cover? 
A Medigap plan , also known as Medicare Supplement insurance , is sold by private companies to help off-set the cost of some health care expenses not covered by Original Medicare does n't cover , like co-payments , coinsurance , and deductibles . One other huge benefit of any Medigap plan is the extension of your hospital coverage -LRB- paid under Medicare Part A -RRB- by an additional 365 days . Some Medigap policies also offer additional coverage for services that Original Medicare does not cover , such as medical care when you travel outside the U.S. . If you have Original Medicare and you buy a Medigap policy , Medicare will pay its share of the Medicare-approved amount for covered health care costs . Then your Medigap policy pays its share . In most states , there are ten standardized Medigap plans , known by letters A through M. Regardless of that state in which you reside , or the company you purchase Plan A will always provide the exact same coverage as any other Plan A . The most popular plan is F , which covers 100 % of all patient cost sharing for Medicare-covered expenses . Plan G is also a popular option , often significantly cheaper than Plan F , with almost the exact same coverage -LRB- G covers everything F does , expect your Medicare Part B deductible -RRB- . 