Who is eligible for Medicare?

Medicare is the federal health insurance program for Americans aged 65 and older who have paid Medicare taxes (or whose spouse has paid Medicare taxes) for at least 10 years (40 quarters). People under 65 may also qualify if they have received Social Security Disability Insurance (SSDI) benefits for 24 months, have End-Stage Renal Disease (ESRD), or have Amyotrophic Lateral Sclerosis (ALS). Medicare is distinct from Medicaid (which is income-based and jointly state-federal). Medicare has four parts: Part A (hospital insurance, usually premium-free for those who paid in), Part B (medical insurance, monthly premium), Part C (Medicare Advantage, private plans replacing A and B), Part D (prescription drug coverage). Most beneficiaries also use Medigap supplemental policies to cover gaps in original Medicare.