What are the differences between Medicare Parts A, B, C, D?

Medicare Part A

What it covers

This Part of Medicare addresses hospital coverage. When Medicare beneficiaries receive inpatient care, their Medicare Part A benefits cover the cost of semi-private rooms, drugs, nursing, meals, and certain other services.

Part A can also cover care received at skilled nursing facilities, hospice sites, nursing homes, and some at-home care. The program pays for a fixed number of inpatient mental health days. In skilled nursing facilities, Medicare will cover certain drug costs. Covered home health services include wound care, injections, physical therapy, medical social services, at-home medical supplies, and more.

Under Medicare Part A, beneficiaries can receive coverage for inpatient hospital care if they have a physician’s order and if the hospital accepts Medicare coverage. Beneficiaries pay a fixed amount based on the number of days that they stay in the hospital and Medicare covers the rest.

Beneficiaries must require more than just custodial care—for example, assistance with bathing or dressing—in order to qualify for nursing home coverage.

What it does not cover

Part A does not cover private nursing, personal care items, a private room (with exceptions), or a room’s television or phone costs.

In hospice care, Medicare Part A does not cover treatments or drugs to cure illnesses because this part of the program primarily covers palliative hospice care. Unless a hospice team arranges it, it also does not cover outpatient hospital treatment, including ambulance transportation, or room and board if you live in a hospice facility or if you are receiving hospice care at home.

Home health needs that extend beyond part-time or intermittent care—up to 8 hours a day or 28 hours a week—will not be covered under Medicare. All-day care, meal deliveries, and homemaker or custodial services are not covered.

Medicare Part B

What it covers

Part B covers medical needs that happen outside the hospital. This encompasses any services or equipment that have been approved to treat a condition. For example, outpatient care and durable medical equipment such as wheelchairs or walkers are all covered under this segment of Medicare.

Part B also includes preventive care coverage. Beneficiaries may receive coverage for an extensive list of preventive and screening services, from cervical cancer screenings and COVID-19 vaccines to yearly wellness visits and medical nutrition therapy services.

Both Parts A and B may cover home health services if the need is part-time or if you only need intermittent skill services. For example, a beneficiary who cannot leave home without assistance may be eligible for home health services coverage.

Certain hospital-related benefits are covered under Part B instead of Part A. Specifically, in emergencies, Medicare Part B covers ambulance services to hospitals and skilled nursing facilities. Airplane or helicopter transportation may be covered if deemed medically necessary.

Under this segment of Medicare, certain benefits have a price cap. Insulin cannot cost more than $35 under Medicare Advantage or when using a pump covered through Part B.

Part B has the most benefits related to mental health and substance abuse care services. These include inpatient mental healthcare from a doctor or provider, outpatient mental health or substance abuse care services that occur outside a hospital, intensive outpatient mental health and substance abuse care programs at specific facilities, partial hospitalization services (under certain conditions), and behavioral health integration services.

What it does not cover

Medicare Part B covers certain drugs, but the list is less extensive than its Part D counterpart. Generally, drugs that cannot be self-administered are covered through Part B. However, there are exceptions like the injectable blood clotting factors which beneficiaries can inject personally.

Many mental health services are covered under Part B. But this segment does not cover outpatient prescription drugs related to mental health conditions or general or psychiatric hospital care for mental or substance use disorders.

Oxygen equipment for air travel is not covered under Medicare Part B, although the segment does insure other oxygen supplies.

Medicare Part C or Medicare Advantage

What it covers

Although it is considered a “Part” of the large public payer program, Medicare Advantage is really a combination of Parts A and B and sometimes Part D along with extra benefits. Medicare-approved health insurers can offer Medicare Advantage plans privately.

One major difference in Part A coverage through Original Medicare compared as opposed to Medicare Advantage’s Part A benefits is that in Original Medicare beneficiaries are covered by any hospital or provider that takes Medicare. Only 1.1% of physicians opted out of Medicare in 2023. As a result, beneficiaries have a large hospital network.

In contrast, under Medicare Advantage, beneficiaries must go to a hospital within the payer’s network. This difference has been a major challenge for Medicare Advantage plans in recent years as hospitals have started dropping their Medicare Advantage contracts due to administrative and financial issues.

Medicare Advantage plans typically include benefits that go beyond traditional Medicare’s offerings. Most beneficiaries are in plans that offer vision, hearing, dental, fitness, and telehealth benefits. Less common Medicare Advantage benefits include over-the-counter benefits, acupuncture, transportation, and Part B rebates.

What it does not cover

Since these plans are privately-run and can offer extra coverage beyond Original Medicare’s parameters, they vary in their benefits. Medicare Advantage plans may not cover clinical research studies or kidney transplants. Hospice care is covered under Original Medicare, not Medicare Advantage.

Medicare Part D

What it covers

Part D covers prescription drugs. Beneficiaries with Original Medicare coverage have to enroll in Medicare Part D separately. In contrast, Medicare Advantage beneficiaries receive Part D coverage as part of their enrollment.

Part D shares some organizational similarities to Medicare Advantage in that private companies run Part D plans under Medicare regulations. As a result, there is some variation from plan to plan regarding what Part D may cover. Additionally, the list of covered drugs may change from year to year.

Each plan has its own formulary, incorporating brand-name and generic prescriptions. Payers offer two drugs for the most popular categories and classes to give beneficiaries options, and they must cover two drugs in each of the six drug categories.

What it does not cover

Part D plans will not cover every brand name and generic drug, so beneficiaries will find they might not have insurance for their preferred prescription. However, if a provider believes that the beneficiary needs a specific drug for her condition not included in her Part D plan’s formulary, the provider may appeal for an exception.