Use the letters as a map, not as four separate insurance policies
Medicare Parts A, B, C, and D describe benefits and ways to receive them. A person usually has Part A and Part B through Original Medicare or receives those benefits through a Medicare Advantage plan, Part C. Drug coverage may be a separate Part D plan or included in Medicare Advantage.
The letters do not answer whether a particular service is covered. Coverage also depends on medical and other criteria, provider or supplier status, network, authorization, plan documents, frequency, setting, and current rules.
Caregivers can help organize this information, but family relationship does not automatically authorize access or decisions. Obtain the person’s permission and the plan’s accepted authorization for the task.
Part A: inpatient and specified facility-based benefits
Part A generally helps cover qualifying:
- inpatient hospital care
- skilled-nursing-facility care
- hospice
- some home health care
Medicare’s Part A overview identifies these core categories (Medicare Part A). Each has its own conditions.
Part A does not mean all care received inside a hospital or nursing home is covered. Hospital observation can be outpatient. Skilled-nursing coverage is limited and conditional. Long-term custodial nursing-home care is excluded when that is the only care needed.
Caregiver tasks include confirming admission status, obtaining discharge notices, checking the skilled need and facility certification, tracking benefit periods and cost sharing, and preserving appeal deadlines.
Part B: outpatient, clinician, equipment, and preventive care
Part B generally helps cover many medically necessary and preventive services, including clinician visits, outpatient care, ambulance under applicable rules, durable medical equipment, mental-health services, therapies, and qualifying home health.
Ask whether the provider accepts Medicare assignment under Original Medicare. Medicare explains that assignment affects whether the provider accepts the Medicare-approved amount as full payment for covered services (Medicare: How to get services). Some providers opt out or do not accept new patients.
For equipment, verify supplier enrollment, order, documentation, purchase or rental status, repair, replacement, and cost sharing. For preventive services, verify frequency and whether additional diagnostic work could create cost.
Part B is not a general personal-care or household-help benefit.
Part C: Medicare Advantage
Part C is not an extra layer added to Original Medicare. It is another way to receive Part A and Part B through a Medicare-approved private plan. Most plans include Part D drug coverage and may offer supplemental benefits.
Medicare states that Medicare Advantage plans must cover almost all medically necessary services Original Medicare covers, while plan rules can include networks, referrals, prior authorization, and varying costs (Medicare: How Medicare works).
Check:
- exact plan name and contract
- service area
- primary clinician selection
- provider, hospital, facility, supplier, and pharmacy networks
- referral and prior-authorization rules
- premium, deductible, copayment, coinsurance, and annual out-of-pocket maximum
- drug formulary and pharmacy rules
- supplemental-benefit eligibility and limits
- out-of-area, emergency, urgent, and travel rules
- Evidence of Coverage and Annual Notice of Change
Do not assume that a provider accepting Medicare accepts a particular Medicare Advantage plan. Confirm with both provider and plan.
Part D: prescription-drug coverage
Part D may be a standalone plan used with Original Medicare or included within Medicare Advantage. Each plan has a formulary, tiers, network pharmacies, cost sharing, and utilization rules.
Build a current medication list with exact name, strength, form, quantity, and frequency. Then verify:
- formulary status
- tier
- preferred pharmacy or mail order
- prior authorization
- step therapy
- quantity limit
- transition supply or exception route
- deductible and cost-sharing stage
Medicare describes prior authorization, step therapy, quantity limits, and exception requests in its drug-plan rules (Medicare drug plan rules). The prescriber may need to submit supporting information.
Never change a medicine because another tier is cheaper without the prescriber. A plan’s formulary can change, so review annual notices and current pharmacy information.
Understand how A, B, C, and D fit together
Common arrangements include:
Original Medicare plus a standalone Part D plan
Part A and Part B pay under Original Medicare rules. The separate Part D plan handles outpatient prescription drugs. The person may also have Medigap for specified Original Medicare cost sharing.
Medicare Advantage with drug coverage
The plan administers Part A, Part B, and usually Part D. Network, authorization, referral, and plan cost rules apply. Separate Medigap cannot be used to supplement Medicare Advantage.
Medicare Advantage without drug coverage
Some plan types may not include drug coverage. Adding a separate Part D plan may be restricted or may affect enrollment. Verify before changing anything.
Medicare with employer, retiree, Medicaid, or military coverage
Coordination rules determine which payer pays first. Do not cancel employer, union, retiree, TRICARE, Medicaid, or other coverage before the administrator explains consequences in writing.
Do not confuse Medigap with Part C
Medigap is private supplemental insurance designed to pay specified gaps in Original Medicare, such as certain deductibles or coinsurance. It does not replace Part A and Part B and generally does not include outpatient drug coverage.
Medigap and Medicare Advantage are different arrangements. Medicare states that a person cannot buy separate Medigap to supplement a Medicare Advantage plan (Medicare: How Medicare works).
Medigap generally pays only when Original Medicare covers the service. It does not turn long-term custodial care into covered care.
Build a one-page coverage profile
With permission, record:
- Medicare number in the protected layer
- Part A and Part B effective dates
- Original Medicare or exact Medicare Advantage plan
- Part D plan if separate
- Medigap insurer and plan letter if applicable
- Medicaid, employer, retiree, VA, or other coverage
- primary and preferred clinicians
- preferred hospital, pharmacy, and suppliers
- plan and Medicare contact numbers
- authorized representative or permission status
- last review date
Do not place full identifiers in a widely shared caregiver sheet. Keep a minimum-necessary quick reference and a secured master record.
Review the governing documents
For Original Medicare, use Medicare.gov, the current Medicare & You handbook, Medicare Summary Notices, and service-specific notices.
For Medicare Advantage and Part D, use:
- Evidence of Coverage
- Annual Notice of Change
- Summary of Benefits
- provider and pharmacy directories, verified directly
- drug formulary
- authorization decisions
- explanation of benefits
- denial and appeal notices
Medicare explains that the Evidence of Coverage gives details about what a plan covers and what the person pays (Medicare Evidence of Coverage). The Annual Notice of Change describes changes for the coming year.
Marketing summaries are not the final word. Keep the current plan documents and written decisions.
Track costs by benefit and plan
Record premiums, deductibles, copayments, coinsurance, out-of-pocket maximum where applicable, drug costs, noncovered items, and payments by other insurance. Use current official figures rather than last year’s amounts.
Original Medicare does not have the same annual out-of-pocket maximum structure as Medicare Advantage. Medigap and other coverage can change exposure. Medicare Advantage maximums do not generally include every type of spending, such as premiums or Part D costs; check the plan.
Do not choose a plan by premium alone. Consider providers, drugs, authorization, service frequency, travel, supplemental benefits, and total likely cost.
Help without taking over
Ask the person how they want help: opening mail, joining calls, organizing medication coverage, comparing documents, or filing an appeal. Speak to them directly and preserve their choices.
HIPAA permissions, plan authorizations, Medicare’s appointed-representative process, and legal personal-representative status are not interchangeable. Use the narrowest appropriate permission.
Do not create an online Medicare or Social Security account in another person’s identity. Do not share login credentials among relatives. Use official representative and account-access processes.
Review annually and after care transitions
Review coverage during the appropriate enrollment period and after a move, loss of employer coverage, nursing or rehabilitation transition, new diagnosis, medication change, provider departure, or eligibility change.
Check whether a special enrollment period applies before assuming a plan can be changed immediately. Do not cancel existing coverage until the effective date and consequences of replacement are confirmed.
If a decision is wrong, follow the notice’s appeal instructions and deadline. SHIP offers free, unbiased Medicare counseling and can help people understand options without selling plans.
The practical purpose of knowing Parts A, B, C, and D is not memorizing letters. It is knowing which payer and document govern the service, what requirements must be met, who may communicate, what the person may owe, and how to challenge an incorrect decision.
Sources
- Medicare: Part A Coverage
- Medicare: How Medicare Works
- Medicare: How to Get Medicare Services
- Medicare: Compare Medicare Advantage Plan Types
- Medicare: Drug Plan Rules
- Medicare: Evidence of Coverage
- Medicare: Long-Term Care Coverage