Medicare Coverage for Senior Health Services: Parts A, B, C, and D Explained

Medicare is the federal health insurance program covering approximately 65 million Americans, most of them 65 or older, according to the Centers for Medicare & Medicaid Services (CMS). Its four distinct parts — A, B, C, and D — cover different slices of the healthcare picture, from hospital stays to prescription drugs, and understanding which part does what is foundational to making smart decisions about how to pay for senior care. What Medicare covers, and what it deliberately does not, shapes nearly every conversation about senior care costs and pricing.

Definition and scope

Medicare is a federal program administered by CMS, established under Title XVIII of the Social Security Act in 1965. It is not means-tested — eligibility is primarily based on age (65+) or qualifying disability status, not income. That distinction separates it sharply from Medicaid for senior care, which is income-and-asset dependent and covers a broader range of long-term services.

The program divides into four parts, each addressing a distinct category of care:

1. Part A — Hospital Insurance: Covers inpatient hospital stays, care in a skilled nursing facility (under specific conditions), hospice care, and some home health services. Most people pay no premium for Part A if they or a spouse worked and paid Medicare taxes for at least 40 quarters, per CMS Medicare basics.

2. Part B — Medical Insurance: Covers outpatient care, physician visits, preventive services, durable medical equipment, and some home health services. The standard monthly premium in 2024 is $174.70, per CMS Medicare Part B costs.

3. Part C — Medicare Advantage: Private insurance plans approved by Medicare that bundle Part A and Part B benefits, often with Part D added. Plans are sold by private insurers and must cover everything original Medicare covers, but may offer additional benefits like dental or vision.

4. Part D — Prescription Drug Coverage: Standalone drug plans added to original Medicare, or included in most Medicare Advantage plans. Coverage and costs vary by plan and formulary.

How it works

Original Medicare (Parts A and B) operates on a fee-for-service model. Medicare pays its share directly to providers who accept Medicare assignment; the beneficiary pays deductibles, coinsurance, and any costs Medicare does not cover.

Part A carries a per-benefit-period deductible of $1,632 in 2024, per CMS inpatient coverage. A skilled nursing facility stay — often triggered after a qualifying 3-day hospital inpatient admission — is covered in full for days 1–20, with a daily coinsurance of $204 for days 21–100, and no Medicare coverage beyond day 100.

That last detail deserves emphasis. Medicare is not a long-term care program. Extended stays in nursing homes or assisted living facilities fall almost entirely outside its scope, which is a persistent source of surprise among families navigating transitioning to senior care.

Part B covers 80% of approved outpatient costs after the annual deductible ($240 in 2024), leaving the beneficiary responsible for the remaining 20% with no out-of-pocket cap under original Medicare alone. Many beneficiaries pair Part B with a Medigap (supplemental) policy to cap that exposure.

Part C replaces original Medicare for those who enroll. Plans must cover all medically necessary services Parts A and B would cover, but may use networks (HMOs or PPOs) and impose prior authorization requirements. The trade-off is potentially lower out-of-pocket costs in exchange for less provider flexibility.

Common scenarios

Post-hospitalization skilled nursing: A beneficiary hospitalized for at least 3 consecutive inpatient days and then transferred to a certified skilled nursing facility qualifies for Part A SNF coverage. Physical therapy, occupational therapy, and skilled nursing services during that window are covered — but custodial care (help with bathing, dressing, eating) is not a Medicare-covered benefit at any stage.

Home health services: Medicare covers medically necessary skilled care at home — wound care, IV medications, skilled nursing visits — when ordered by a physician and provided by a Medicare-certified agency. It does not cover ongoing in-home senior care of a custodial or personal-care nature.

Hospice: Part A covers hospice for beneficiaries with a life expectancy of 6 months or less, as certified by a physician. The focus shifts from curative to comfort-focused care. Room and board in a facility is generally not included unless the hospice arranges inpatient respite, covered for up to 5 consecutive days per CMS hospice benefit.

Prescription drugs: Without Part D or a Medicare Advantage plan that includes drug coverage, beneficiaries have no Medicare drug benefit at all. The 2024 out-of-pocket cap for Part D is $8,000 under the Inflation Reduction Act's provisions, per CMS Part D updates.

Decision boundaries

Choosing between original Medicare and Medicare Advantage hinges on four variables: provider network preferences, anticipated service utilization, geographic availability of plans, and willingness to navigate prior authorization. Original Medicare allows visits to any Medicare-accepting provider nationwide — relevant for snowbirds or seniors receiving care in multiple locations.

Medicare Advantage plans numbered 3,959 nationally in 2024, per KFF Medicare Advantage analysis, providing strong availability in most urban and suburban markets but thinner options in rural counties.

For those whose care needs extend beyond what Medicare covers — memory care, assisted living, or extended custodial care — long-term care insurance and Medicaid planning become the relevant financial tools. Medicare is a strong foundation, but it was designed for acute and post-acute care, not the sustained support that conditions like dementia demand. For a fuller picture of how these funding sources interact, the how to pay for senior care section maps the landscape in detail.