Medicare and Medicaid Covered Services
Medicare and Medicaid together cover more than 150 million Americans — roughly 45% of the U.S. population — making them the two largest purchasers of healthcare in the country. What those programs actually pay for, however, is more specific than most people realize, shaped by federal statute, state policy, and a layered system of coverage categories that behave quite differently from commercial insurance. Understanding how covered services are defined, limited, and administered under each program can mean the difference between a $0 bill and an unexpected four-figure balance.
Definition and scope
Medicare is a federal health insurance program established under Title XVIII of the Social Security Act, administered by the Centers for Medicare & Medicaid Services (CMS). It covers adults 65 and older, certain younger people with qualifying disabilities, and individuals with end-stage renal disease. Medicaid, established under Title XIX of the same Act, is a joint federal-state program serving low-income individuals and families, with eligibility and benefit scope varying by state.
The phrase "covered services" refers to specific categories of medical care that each program is obligated — or permitted — to pay for, within defined parameters. Medicare's mandatory coverage categories are set in federal law. Medicaid's mandatory and optional benefit categories are outlined in 42 CFR Part 440, with states granted significant latitude to expand or restrict optional services. This structural difference is important: a service covered by Medicaid in California may not be covered in Texas.
For a broader grounding in how coverage interacts with insurance coverage for medical services, CMS publishes the Medicare Benefit Policy Manual (Publication 100-02), which is the primary reference document for Medicare coverage determinations.
How it works
Medicare is divided into four parts, each covering a distinct category of care:
- Part A (Hospital Insurance) — Covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health services. Most enrollees pay no premium for Part A if they or their spouse paid Medicare taxes for at least 40 quarters.
- Part B (Medical Insurance) — Covers outpatient care, physician services, preventive services, durable medical equipment, and certain mental health medical services. The standard Part B premium in 2024 is $174.70 per month (CMS, 2024).
- Part C (Medicare Advantage) — Private plans that cover all Part A and B services, often with additional benefits such as dental, vision, and hearing.
- Part D (Prescription Drug Coverage) — Covers outpatient prescription medications through private plan sponsors under CMS contract.
Medicaid coverage is structured differently. States must cover 17 mandatory benefit categories — including inpatient and outpatient hospital services, physician services, and home health medical services — as defined in 42 CFR §440.210 and §440.220. Beyond those floors, states may add optional services, including dental, vision, personal care, and long-term care medical services. As of 2023, 40 states and the District of Columbia had adopted the ACA Medicaid expansion, extending coverage to adults with incomes up to 138% of the federal poverty level (KFF State Health Facts).
A service must typically meet three criteria to be covered: it must fall within a recognized benefit category, be deemed medically necessary under program standards, and be furnished by an enrolled provider.
Common scenarios
Hospital admission: A Medicare beneficiary admitted for pneumonia triggers Part A coverage. The 2024 Part A inpatient deductible is $1,632 per benefit period (CMS). Days 1–60 are covered after the deductible; days 61–90 carry a $408 daily coinsurance.
Preventive care: Under Part B, Medicare covers an Annual Wellness Visit at no cost-sharing, along with colorectal cancer screening, mammography, and preventive medical services flagged with an "A" or "B" rating by the U.S. Preventive Services Task Force.
Pediatric dental under Medicaid: For children, Medicaid's Early and Periodic Screening, Diagnostic and Treatment (EPSDT) mandate — established under 42 U.S.C. §1396d(r) — requires states to cover any medically necessary service, even if that service falls outside the standard adult benefit package. This is one of Medicaid's most expansive provisions, and one of its least commonly understood. Medical services for children and pediatrics operate under a markedly different coverage logic than adult Medicaid.
Telehealth: Following regulatory changes codified in the Consolidated Appropriations Act of 2023, Medicare expanded permanent coverage for certain telehealth and virtual medical services, including mental health services delivered via two-way audio-visual technology.
Decision boundaries
The line between covered and non-covered is drawn in three places: statutory definition, medical necessity determination, and prior authorization for medical services.
Medicare does not cover routine dental care, routine vision exams, hearing aids, or most cosmetic procedures under traditional Parts A and B — these exclusions are explicit in 42 U.S.C. §1395y. Medical necessity is assessed against Local Coverage Determinations (LCDs) and National Coverage Determinations (NCDs) published by CMS, which set the clinical criteria a service must meet to be reimbursed.
The contrast between Medicare and Medicaid is sharpest at the long-term care boundary. Medicare covers skilled nursing facility care for up to 100 days per benefit period, but only following a qualifying inpatient hospital stay of at least 3 consecutive days. Medicaid, by contrast, is the primary payer for custodial long-term care — nursing home stays that extend months or years — a distinction with profound financial consequences for medical services for seniors navigating care transitions.
Dual-eligible individuals — those who qualify for both Medicare and Medicaid simultaneously, numbering approximately 12.5 million as of 2022 (CMS Dual Eligible Data) — face the most complex coverage determinations, as the two programs coordinate payment through specific sequencing rules that govern which payer acts first.