Medicare is primarily available to individuals aged 65 and older who are citizens or permanent residents of the United States and have lived in the country for at least five continuous years. However, certain younger people with disabilities and those with End-Stage Renal Disease (ESRD) may also qualify for Medicare coverage. Individuals under 65 can qualify for Medicare if they have been receiving Social Security Disability Insurance (SSDI) benefits for at least 24 months or if they have certain disabilities such as amyotrophic lateral sclerosis (ALS). Additionally, individuals of any age with ESRD, such as those requiring regular dialysis or a kidney transplant, are eligible for Medicare coverage, regardless of their age or work history.

Medicare Parts A and B form the foundation of the federal health insurance program, providing essential coverage for hospital and medical services, respectively. Medicare Part A, often referred to as Hospital Insurance, covers inpatient hospital care, skilled nursing facility stays, hospice care, and some home health services. Part A is generally premium-free for most beneficiaries who have paid Medicare taxes during their working years. Medicare Part B, known as Medical Insurance, covers outpatient services like doctor visits, preventive care, medical supplies, and some home health services. Beneficiaries typically pay a monthly premium for Part B coverage, along with deductibles and coinsurance. Together, Parts A and B offer comprehensive coverage for a wide range of healthcare needs, forming the cornerstone of Medicare's benefits.