Why Do You Need Medigap Insurance? 
Medigap Insurance , also called `` Medicare Supplement '' Insurance works with original Medicare -LRB- Parts A and B -RRB- to provide coverage for the `` gaps '' - the coinsurance and deductibles required to be paid by the Medicare beneficiary -LRB- consumer -RRB- under original Medicare . Although Medicare represents excellent insurance coverage , these `` gaps '' can be expensive for the consumer . For example , the Part A -LRB- hospitalization -RRB- deductible for 2015 is $ 1,260 , and the Part B -LRB- doctors costs , etc. -RRB- is $ 147 plus 20 % coinsurance . A Medigap policy insures these potentially large `` gaps '' with the payment of a known monthly premium . Medigap Insurance is optional for the consumer - there is no `` requirement '' to purchase it , although it is a good idea to get some Medigap coverage if staying with original Medicare . Alternatively , Medicare beneficiaries may select a Medicare Advantage Plan . Although there are costs and limitations in Medicare Advantage Plans , a beneficiary does not need , nor can they purchase Medigap Insurance under a Medicare Advantage Plan . 