Medicare, the federal health insurance program that covers 41 million Americans, has played a central role in the U.S. health system since it was established in 1965. Medicare serves all eligible beneficiaries without regard to income or medical history.
Most individuals ages 65 and over are automatically entitled to Medicare Part A (the Hospital Insurance Program) if they or their spouse are eligible for Social Security payments. People under 65 who receive Social Security cash payments due to a disability generally become eligible for Medicare after a two-year waiting period. People with end-stage renal disease (ESRD) are entitled to Part A regardless of their age. Part B (the Supplementary Medical Insurance Program) is voluntary, but covers 95% of all Part A beneficiaries.