Medicare was never intended to pay 100% of your medical bills. But, instead it was created to offset your most pressing medical expenses by providing a basic foundation of benefits. Thus, while it will pay a significant portion of your medical bills, Medicare will not cover all services that you might need. Medicare requires that you pay deductibles. Medicare also pays Part B expenses at 80% of the Medicare approved amount.
Insurance companies sell policies that pay some of these expenses if you are enrolled in both Part A and Part B of Medicare. These policies are referred to as Medicare Supplement policies. They provide a way to fill the coverage gaps left by Medicare. You are automatically eligible for individual Medicare Supplement coverage for six months, starting with the first day you are enrolled in Medicare Part B, regardless of your health history. This is the guaranteed-issue period.
An agent or insurance company must give you an Outline of Coverage when selling you a new policy or replacing one you already own. The Outline of Coverage contains a chart summarizing the benefits provided by Medicare Parts A and B and the benefits provided by the Medicare Supplement policy.