Medicare is a federal health insurance program primarily available to individuals age 65 and older , as well as certain younger individuals with disabilities. Medicare is divided into several parts, each covering different types of healthcare services. Medicare Part A , also known as Hospital Insurance , covers inpatient hospital care, skilled nursing facility care, hospice care, and some limited home health services.

Individuals who qualify for Medicare—especially those already receiving Social Security retirement benefits —are typically automatically enrolled in Medicare Part A when they reach age 65. Coverage generally begins on the first day of the month in which the individual turns 65 (or the prior month if their birthday falls on the first day of the month). Because most individuals have paid Medicare taxes through payroll contributions during their working years, Part A usually requires no monthly premium .

Medicare Part B (Medical Insurance), which covers physician services, outpatient care, and preventive services, requires a monthly premium and may require active enrollment if the individual is not automatically enrolled. Part C refers to Medicare Advantage plans offered by private insurers, and Part D provides prescription drug coverage. Therefore, the part of Medicare that eligible individuals are automatically enrolled in is Medicare Part A .