5.1 Medicare Architecture and Covered Services

Medicare Architecture and Covered Services

Healthcare represents one of the largest and most volatile expenditure categories facing retirees. A comprehensive retirement plan must accurately anticipate medical expenses, structure optimal insurance coverage, and guard against catastrophic out-of-pocket liabilities. Originally enacted in 1965 under Title XVIII of the Social Security Act, Medicare serves as the federal health insurance foundation for Americans aged 65 and older, as well as qualified individuals with permanent disabilities, End-Stage Renal Disease (ESRD), or Amyotrophic Lateral Sclerosis (ALS).

Medicare is divided into four distinct components: Part A (Hospital Insurance), Part B (Medical Insurance), Part C (Medicare Advantage), and Part D (Prescription Drug Coverage). Understanding how these parts interact, what they cover, what they exclude, and where dangerous out-of-pocket gaps remain is essential for retirement counselors.

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Part A: Hospital Insurance Architecture

Medicare Part A covers acute medical care when an individual is formally admitted as an inpatient. It is financed primarily through the mandatory Hospital Insurance (HI) payroll tax of 2.9% (1.45% paid by the employee and 1.45% by the employer) under the Federal Insurance Contributions Act (FICA). Self-employed individuals pay the full 2.9%. Under the Affordable Care Act (ACA), an Additional Medicare Tax of 0.9% applies to earned income exceeding $200,000 for single taxpayers and $250,000 for married couples filing jointly.

Eligibility and Entitlement

Beneficiaries qualify for premium-free Part A if they or their spouse earned at least 40 Social Security work credits (approximately 10 years of covered employment). Spousal eligibility requires the couple to have been married for at least one year before filing, and the worker must be at least age 62 (even though the applicant must be 65). Divorced spouses can qualify on a former spouse's earnings record if the marriage lasted at least 10 years.

Individuals who reach age 65 without 40 credits may purchase Part A coverage by paying a monthly premium. Those with 30 to 39 credits pay a reduced monthly premium (approximately $311 in 2026 in recent statutory adjustments), while individuals with fewer than 30 credits pay the full monthly premium (approximately $565 in 2026).

Covered Inpatient Services

Part A provides coverage for four distinct care settings:

1. Inpatient Hospital Care: Semi-private room, general nursing, meals, operating room costs, intensive care, diagnostic imaging, and drugs administered during an inpatient admission.
2. Skilled Nursing Facility (SNF) Care: Short-term skilled nursing rehabilitation following a qualifying hospital stay.
3. Home Healthcare Services: Intermittent skilled nursing care, physical therapy, speech therapy, and continued occupational therapy ordered by a physician for homebound beneficiaries.
4. Hospice Care: Palliative comfort care and pain management for terminally ill patients certified with a life expectancy of 6 months or less. Hospice care carries no Part A deductible and requires only nominal copayments for outpatient prescription drugs (up to $5 per prescription) and 5% coinsurance for respite care.

The Part A Benefit Period Mechanism

Unlike private commercial health insurance and Medicare Part B, Part A cost-sharing does not operate on a calendar-year deductible. Instead, Part A uses a benefit period (also referred to as a "spell of illness").

• A benefit period begins the day a beneficiary enters a hospital or skilled nursing facility as an inpatient.
• The benefit period ends after 60 consecutive days without inpatient hospital care or skilled care in a SNF. Remaining in a facility for custodial care alone does not necessarily keep the period open.
• If the beneficiary is re-hospitalized after 60 consecutive days out of the facility, a new benefit period begins, requiring payment of a new Part A hospital deductible.
• There is no limit to the number of benefit periods a beneficiary can experience over their lifetime. A retiree admitted to the hospital three times in a single year—separated each time by more than 60 days—must pay the full Part A deductible three times.

Inpatient Hospital Cost-Sharing Schedule

Within each separate benefit period, the beneficiary's cost-sharing escalates based on the length of the stay:

• Days 1–60: The beneficiary pays the statutory Part A Deductible (e.g., $1,736) for the entire 60-day block. Medicare pays 100% of remaining covered charges. There is no daily copayment.
• Days 61–90: The beneficiary pays a mandatory daily coinsurance equal to 1/4 of the Part A deductible (e.g., $434 per day).
• Days 91–150 (Lifetime Reserve Days): The beneficiary may draw upon a once-in-a-lifetime pool of 60 non-renewable lifetime reserve days. The daily coinsurance is equal to 1/2 of the Part A deductible (e.g., $868 per day).
• Beyond 150 Days: Once lifetime reserve days are exhausted, the beneficiary pays 100% of all hospital expenses out of pocket.

Skilled Nursing Facility (SNF) Coverage Rules

Medicare Part A coverage for skilled nursing is strictly rehabilitative and short-term. To trigger SNF coverage, three mandatory statutory criteria must be satisfied:

1. Qualifying Hospital Stay: The beneficiary must have a formal inpatient hospital stay of at least 3 consecutive inpatient days, excluding the discharge day. Time spent under "observation status" in an emergency room or hospital bed does not count toward the 3-day requirement.
2. Timely Admission: The patient must be admitted to a Medicare-certified SNF within 30 days of hospital discharge for the same medical condition or a condition that arose while receiving treatment.
3. Daily Skilled Need: The patient must require daily skilled nursing or skilled therapy services that can only practically be provided in an inpatient facility.

If these conditions are met, Part A covers up to 100 days of SNF care per benefit period:

• Days 1–20: Covered at 100% (beneficiary pays $0 copayment).
• Days 21–100: The beneficiary pays a daily coinsurance equal to 1/8 of the Part A deductible (e.g., $217 per day).
• Days 101 and beyond: The beneficiary pays 100% of all costs. The 100-day maximum is per benefit period; ongoing eligibility and a new benefit period must be evaluated. Medicare does not cover a stay consisting only of custodial care.

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Part B: Medical Insurance Architecture

Medicare Part B covers outpatient medical services, physician care, and medical supplies necessary to diagnose or treat health conditions. Part B is an elective program funded through a combination of general federal tax revenues (approximately 75%) and beneficiary monthly premiums (approximately 25%).

Covered Outpatient Services

• Physician and Specialist Services: Consultations, office visits, surgical procedures, and second opinions.
• Outpatient Hospital Care: Emergency room visits, same-day surgical center procedures, and observation services.
• Diagnostic Testing: Clinical laboratory blood tests, X-rays, MRIs, CT scans, and specialized diagnostic procedures.
• Durable Medical Equipment (DME): Wheelchairs, walkers, hospital beds, oxygen equipment, and blood sugar monitors prescribed by a physician for home use.
• Preventive Services: "Welcome to Medicare" preventive visit, annual "Wellness" visits, cardiovascular screenings, mammograms, colonoscopies, and flu/pneumonia vaccines (generally covered at 100% with no deductible or coinsurance).
• Outpatient Mental Health: Psychiatric therapy, counseling, and substance abuse treatment.

Original Medicare Exclusions

Neither Part A nor Part B covers several critical healthcare needs commonly required by aging individuals:

• Routine dental care, cleanings, and dentures
• Routine vision exams, eyeglasses, and contact lenses
• Routine hearing exams for fitting hearing aids and the hearing aids themselves; medically necessary diagnostic hearing testing can be covered
• Cosmetic surgery
• Long-term custodial care (assistance with activities of daily living like dressing, bathing, and eating)
• Medical care received outside the United States (except under extremely narrow emergency exceptions near the Canadian or Mexican border)

Part B Cost-Sharing and the Catastrophic Exposure Trap

Part B cost-sharing follows a standard annual fee-for-service design:

1. Monthly Premium: Beneficiaries pay a standard monthly premium (e.g., $202.90 in 2026), deducted directly from monthly Social Security benefit checks. Higher earners pay an Income-Related Monthly Adjustment Amount (IRMAA).
2. Annual Deductible: An annual calendar-year deductible (e.g., $283 in 2026) must be satisfied before Medicare begins cost-sharing.
3. 80/20 Coinsurance: After the deductible is met, Medicare pays 80% of the Medicare-approved amount for covered services. The beneficiary is responsible for the remaining 20% coinsurance.

Critical Financial Planning Concept: Original Medicare (Part A and Part B combined) contains no statutory annual or lifetime Maximum Out-of-Pocket (MOOP) limit. A beneficiary with severe illness requiring $300,000 of outpatient oncology infusions or complex surgical interventions owes 20% of that total—or $60,000—directly out of pocket. Without supplemental coverage, Part B coinsurance presents an uncapped catastrophic financial risk to retirement portfolios.

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Part C: Medicare Advantage Architecture

Medicare Part C, known as Medicare Advantage (MA), is an alternative delivery system created under the Balanced Budget Act of 1997. Under Part C, private commercial health insurers (such as UnitedHealthcare, Humana, Aetna, or Blue Cross Blue Shield) contract with the Centers for Medicare & Medicaid Services (CMS) to administer the beneficiary's Medicare benefits.

Regulatory Requirements and Mechanics

• Coverage Equivalence: By federal statute, a Medicare Advantage plan must cover all services provided under Part A and Part B (with the sole exception of hospice care, which remains covered directly through Original Part A).
• Private Plan Choices: MA plans typically operate as Health Maintenance Organizations (HMOs) or Preferred Provider Organizations (PPOs).
• Network Restrictions: HMO plans mandate that beneficiaries receive care exclusively within a contracted geographic network of doctors and hospitals, requiring referrals from a Primary Care Physician (PCP) to see specialists. PPO plans allow out-of-network care but impose significantly higher deductibles and coinsurance.
• Mandatory MOOP Protection: Unlike Original Medicare, CMS mandates that every Medicare Advantage plan establish a legally binding annual Maximum Out-of-Pocket (MOOP) limit for covered Part A and Part B services. The plan must disclose its annual in-network maximum within CMS limits; use the actual 2026 Evidence of Coverage, protecting enrollees against limitless catastrophic medical bills.
• Supplementary Benefits: To attract enrollees, MA plans frequently bundle routine dental, vision hardware, hearing aids, fitness center memberships (e.g., SilverSneakers), and transportation assistance.

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Part D: Prescription Drug Benefit Architecture

Enacted under the Medicare Prescription Drug, Improvement, and Modernization Act of 2003 (MMA) and launched in 2006, Medicare Part D provides outpatient prescription drug coverage. Part D is offered exclusively through private insurance companies, either as a Stand-alone Prescription Drug Plan (PDP) that supplements Original Medicare, or bundled into a Medicare Advantage Prescription Drug plan (MA-PD).

Every Part D plan develops a specific formulary (approved drug list) organized into tiers (Tier 1 Preferred Generic, Tier 2 Generic, Tier 3 Preferred Brand, Tier 4 Non-Preferred Drug, and Tier 5 Specialty Tier). Copayments and coinsurance percentages escalate as drugs move up the tier hierarchy.

Historical Structure vs. Landmark Inflation Reduction Act Reforms

Historically, standard statutory Part D plans featured four distinct coverage phases:

1. The Annual Deductible Phase
2. The Initial Coverage Phase
3. The Coverage Gap (notoriously known as the "Donut Hole")
4. Catastrophic Coverage (where enrollees still paid 5% coinsurance indefinitely)

The passage of the Inflation Reduction Act (IRA) of 2022 fundamentally reshaped Part D, phasing in monumental structural reforms that fully matured by 2025–2026:

• Elimination of Catastrophic Coinsurance: The 5% coinsurance requirement during the catastrophic coverage phase was permanently eliminated, cutting catastrophic out-of-pocket costs to $0.
• Annual Part D out-of-pocket threshold: The threshold was $2,000 in 2025 and is $2,100 in 2026. Once an enrollee reaches the applicable annual amount in in qualifying out-of-pocket prescription expenses, they pay $0 for covered medications for the remainder of that year.
• Prescription Payment Plan (Smoothing Option): Beneficiaries have the statutory right to spread their covered Part D out-of-pocket prescription costs across capped monthly installments over the calendar year, eliminating the severe early-year cash flow shock for high-cost specialty drugs.
• Insulin Price Cap: Cost-sharing for a 30-day supply of covered insulin products is legally capped at $35 per month or less for each covered Part D insulin. In 2026 the limit is the lesser of $35, 25% of the applicable maximum fair price, or 25% of the negotiated price, with no deductible applicable.
• Vaccine Coverage: Adult vaccines covered under Part D and recommended by the Advisory Committee on Immunization Practices (ACIP)—including Shingrix (shingles), tetanus, are covered at $0 cost-sharing (no deductible or copayment).

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Medicare Architecture Comparison

The following table summarizes the operational and structural differences across the four parts of Medicare:

Retirement counselors must evaluate these foundational structures when auditing a client's healthcare readiness. Relying on Original Medicare alone leaves major catastrophic exposures through the uncapped 20% Part B coinsurance, the recurring Part A benefit period deductible, and complete exclusions for dental, vision, hearing, and long-term custodial care.

Sources and review date

Checked October 19, 2026: CMS 2026 Medicare costs. Annual limits apply to the year explicitly identified; examples state their assumptions.

Part D details: CMS 2026 benefit announcement. Some Medicare Advantage plans and authorized demonstrations waive the usual three-day SNF prerequisite. The ordinary Original Medicare rule counts inpatient days, not a mandatory 72-hour stopwatch, and skilled coverage is not limited to improvement when maintenance therapy is medically necessary.