Authorized in 1965, becoming Title XIX of the Social Security Act. Medicaid is a state–federal partnership jointly funded by the states and federal government and administered by the states according to federal requirements to assist states in providing medical care to eligible people. Within broad federal guidelines, each state establishes its own eligibility standards; determines the type, amount, duration, and scope of services; sets the rate of payment for services; and administers its own program.
Medicaid is the largest program providing medical and health-related services to low-income people. Medicaid was originally available only to people receiving cash assistance, but over time, Congress has expanded eligibility for children and selected adult groups. The Patient Protection Affordable Care Act (ACA) (P.L. 111–148) and the Health Care and Education Reconciliation Act of 2010 (HCERA) (P.L. 111–152) initiated significant changes to Medicaid. Subsequent references to ACA in Health, United States include changes enacted by ACA or HCERA.
States are mandated by federal law to cover certain population groups but are granted flexibility in covering other groups (42 USC 1396 et seq). In the standard benefit package, states must cover mandatory benefits (for example, physician services) but may choose to cover optional benefits (for example, tuberculosis-related services). States set individual eligibility criteria within federal minimum standards. Before ACA, many states expanded Medicaid coverage above the federal minimums, and many states have chosen to continue this additional coverage.
Broadly, there are four major eligibility groups covered by most states: Children, Adults with Disabilities, Aged Adults, and Nondisabled Adults. Detailed discussion of each group follows.