Understanding the Core of Original Medicare
Original Medicare is built on two foundational parts: Part A and Part B. Together, they cover a broad range of medical services — but they work very differently. Knowing the distinctions helps you understand what to expect when you need care and how much you'll pay out of pocket.
Medicare Part A: Hospital Insurance
Part A is often called "hospital insurance" because its primary function is covering inpatient care. Here's what it includes:
What Part A Covers
- Inpatient hospital stays — semi-private room, meals, nursing services, and medications administered during your stay
- Skilled nursing facility (SNF) care — but only following a qualifying inpatient hospital stay of at least 3 days
- Hospice care — for terminal illnesses when curative treatment is no longer pursued
- Home health care — limited to medically necessary, part-time skilled nursing or therapy services
- Inpatient mental health care — in psychiatric facilities up to 190 days in a lifetime
What Part A Does NOT Cover
- Private hospital rooms (unless medically necessary)
- Personal comfort items (TV, phone, private duty nursing)
- Long-term custodial care (help with daily activities)
Part A Costs
- Premium: $0 for most people (if you or your spouse paid Medicare taxes for 40+ quarters)
- Inpatient deductible: A set amount per benefit period (adjusted annually by CMS)
- Coinsurance: Applies after the 60th day of a hospital stay, and increases for longer stays
Medicare Part B: Medical Insurance
Part B covers outpatient and preventive care — the services you typically receive outside of a hospital setting.
What Part B Covers
- Doctor visits — primary care and specialist appointments
- Outpatient procedures — surgeries, lab tests, X-rays, and imaging
- Preventive services — annual wellness visits, flu shots, mammograms, colonoscopies, and more (often at no cost)
- Durable medical equipment (DME) — wheelchairs, walkers, oxygen equipment, blood glucose monitors
- Mental health services — outpatient therapy and counseling
- Ambulance services — when medically necessary
- Some home health care — in coordination with Part A
What Part B Does NOT Cover
- Prescription drugs (covered by Part D)
- Routine dental, vision, or hearing care
- Cosmetic surgery
- Acupuncture (with limited exceptions)
Part B Costs
- Monthly premium: Determined annually by CMS; higher earners pay more (Income-Related Monthly Adjustment Amount, or IRMAA)
- Annual deductible: Set annually by CMS; you pay this before Medicare begins covering services
- Coinsurance: Typically 20% of the Medicare-approved amount after the deductible is met
Side-by-Side Comparison
| Feature | Part A | Part B |
|---|---|---|
| Type of care | Inpatient / hospital | Outpatient / medical |
| Premium for most | $0 | Monthly premium applies |
| Deductible structure | Per benefit period | Annual |
| Coinsurance | Varies by length of stay | 20% after deductible |
| Drug coverage | In-hospital drugs only | No (Part D needed) |
| Preventive care | Limited | Broad coverage, often free |
Do You Need Both?
Most Medicare beneficiaries enroll in both Part A and Part B — together they form the backbone of comprehensive healthcare coverage. While Part A enrollment is often automatic for those already receiving Social Security, Part B requires active enrollment and payment of a monthly premium. Unless you have other creditable coverage, enrolling in both is generally the right move.