What Medicare Is and How It Works
Medicare is a federal health insurance program that primarily serves people age 65 and older. The program began in 1965 as part of the Social Security Act. Today, roughly 68 million Americans receive Medicare coverage, according to the Centers for Medicare & Medicaid Services. Beyond age-based enrollment, Medicare also covers some younger people with permanent disabilities, people with end-stage renal disease, and people with ALS (Lou Gehrig's disease).
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The program operates through different parts, each covering different aspects of health care. This structure means that understanding how Medicare works requires learning what each part does and how they interact. The program is funded through payroll taxes, premiums, and general federal revenue. When you turn 65, you become eligible to participate based on age alone if you meet certain residency requirements—you must be a U.S. citizen or permanent resident for at least five years.
Medicare functions differently from typical private insurance. Instead of shopping for coverage like you might with employer-based insurance, Medicare offers standardized plans with predictable rules. The federal government sets these rules and pays providers based on Medicare's fee schedules. Private insurance companies do participate in Medicare, but they operate within the framework the government establishes.
Understanding Medicare's basic structure is important because the program has many moving parts. Some parts are managed directly by the government, while other parts involve private insurance companies. Knowing which part covers which service helps you navigate the system more effectively. Many people find that taking time to learn how Medicare works prevents confusion and mistakes later on.
Practical takeaway: Medicare has different parts for different services. Learning what Part A, Part B, Part D, and Medigap cover helps you understand what costs you might face for different types of care.
Medicare Part A: Hospital and Inpatient Care Coverage
Medicare Part A covers inpatient hospital services, skilled nursing facility care, hospice care, and some home health services. When you are admitted to a hospital as an inpatient—meaning you stay overnight or longer—Part A covers your hospital bed, meals, medications while in the hospital, and basic medical services. Most people do not pay a monthly premium for Part A because they paid into it through payroll taxes during their working years.
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However, Part A does come with out-of-pocket costs when you use services. These costs include a deductible, which in 2024 is $1,632 per benefit period. A benefit period begins the day you enter a hospital and ends after you have not received inpatient hospital or skilled nursing facility care for 60 consecutive days. After you pay the deductible, you pay copayments for longer stays. For days 1-60 in a hospital, there is no copayment beyond the deductible. For days 61-90, the copayment is $408 per day in 2024. After 90 days, you enter "lifetime reserve days," which come with higher costs.
Skilled nursing facility care is different from regular nursing home care. Part A only covers skilled nursing care—meaning the care requires skilled nursing or therapy services. If you need only custodial care (help with daily living activities), Part A does not cover it. To qualify for skilled nursing facility coverage, you typically must have been hospitalized for at least three days and then move to a facility within 30 days. Part A covers the first 20 days fully (after the hospital deductible), and days 21-100 with a copayment of $204 per day in 2024.
Hospice and home health services under Part A serve people with terminal illnesses or chronic conditions. Hospice provides comfort-focused care, and Medicare covers most hospice services without requiring you to pay a copayment, though you may pay a small copayment for certain medications and respite care. Home health services cover skilled nursing or therapy in your home, with no copayment when using a Medicare-certified home health agency.
Practical takeaway: Part A primarily protects you from very high hospital and nursing facility costs, but it has time limits and copayments for extended stays. Understanding these limits helps you plan for potential costs and explore supplemental coverage options.
Medicare Part B: Doctor Visits and Outpatient Services
Medicare Part B covers doctor services, outpatient hospital services, diagnostic tests, medical equipment, and some preventive services. This is the part of Medicare that covers your regular visits to your primary care doctor or specialists. Part B also covers emergency room visits, lab work, X-rays, and imaging services like CT scans or MRIs when medically necessary. Unlike Part A, most people pay a monthly premium for Part B. In 2024, the standard Part B premium is $164.90 per month, though higher-income beneficiaries pay more.
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Part B has an annual deductible, which in 2024 is $240. Once you meet this deductible, you typically pay 20 percent of the approved amount for most services, while Medicare pays 80 percent. This means your costs depend on the type of service and the provider's charges. If a provider is "in-network" with Medicare (meaning they accept Medicare's approved amount as payment in full), your out-of-pocket cost is limited to your 20 percent share. If a provider does not accept Medicare assignment, you could owe more.
Preventive services covered under Part B often require no copayment or coinsurance if you use an in-network provider. These include annual wellness visits, cardiovascular screenings, cancer screenings like mammograms and colonoscopies, bone density testing, and vaccines such as flu, pneumonia, and shingles vaccines. Starting these preventive services at age 65 can help catch health conditions early when they are easier to treat.
Mental health services, including therapy and psychiatric care, are covered under Part B with the same 20 percent coinsurance. Rehabilitation services like physical therapy are covered when medically necessary, though there are limits on the number of visits per year. Durable medical equipment such as wheelchairs, oxygen equipment, and walkers are also covered, usually with you paying 20 percent of the approved amount after meeting your deductible.
Practical takeaway: Part B protects against major costs for doctor visits and outpatient services, but you share costs through premiums, deductibles, and coinsurance. Knowing which services are preventive (and therefore covered without additional cost) helps you stay on top of your health without surprise bills.
Medicare Part D: Prescription Drug Coverage
Medicare Part D provides coverage for prescription medications. This part is delivered through private insurance companies that contract with Medicare, so you must choose a specific Part D plan. Unlike Parts A and B, Part D is optional, but there is a financial penalty for delaying enrollment if you do not have other creditable drug coverage. If you delay signing up for Part D without good reason, you pay a higher premium for each month you were not enrolled, and this penalty is permanent.
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Part D plans have different structures, but most follow a predictable cost pattern throughout the year. First, you pay a monthly premium, which varies by plan (typically $7 to $100+ per month in 2024). Then you pay out-of-pocket costs until you reach your deductible, which most plans set between $0 and $545 in 2024. After meeting the deductible, you enter the initial coverage stage, where you typically pay a copayment or coinsurance for each prescription. Generic drugs usually cost less than brand-name drugs.
Once you and your insurance plan have paid a combined total of $5,850 in 2024, you enter the coverage gap, sometimes called the "donut hole." In the donut hole, you pay a higher percentage of drug costs—currently 25 percent of the cost of brand-name drugs and generics. However, manufacturers provide rebates on brand-name drugs, and you receive a discount on generic drugs. The coverage gap phase continues until your total out-of-pocket spending reaches $8,550 in 2024. At that point, you enter catastrophic coverage, where you pay only 5 percent coinsurance for covered drugs for the rest of the year.
Part D plans vary significantly in which drugs they cover and at what tier (copayment level). Drugs are typically organized into tiers: generic drugs have the lowest copayments, preferred brand-name drugs are in the middle, and non-preferred brand-name drugs or specialty drugs have the highest copayments. If a drug you take is in