Medicare Part A covers hospital and inpatient care. Part B covers doctor visits, outpatient services, and preventive care. Together, they form “Original Medicare,” which is what most people receive when they first enroll at age 65. Understanding exactly what falls under each part helps you anticipate your costs and avoid surprises.
What Part A Covers
Part A is hospital insurance. It pays for care you receive as an inpatient, meaning you’ve been formally admitted to a hospital. That includes your semi-private room, meals, general nursing care, medications administered during your stay, and other hospital services and supplies tied to your treatment.
Part A also covers three other major categories beyond standard hospital stays:
- Skilled nursing facility care: If you need rehabilitation or skilled nursing after a hospital stay, Part A covers up to 100 days per benefit period. There’s an important catch: you must have spent at least 3 consecutive days as a hospital inpatient (not counting the discharge day) before the skilled nursing benefit kicks in.
- Home health services: If you’re homebound and need part-time skilled nursing, physical therapy, occupational therapy, or speech therapy, Part A covers those visits along with medical supplies and durable medical equipment used at home. Home health aides who help with bathing, grooming, or feeding are covered too, but only when you’re also receiving skilled care.
- Hospice care: For people with a terminal illness who choose comfort-focused care, Part A covers the hospice benefit.
Blood transfusions received as a hospital inpatient also fall under Part A. However, you’re responsible for the cost of the first 3 units of blood per calendar year, unless someone donates blood on your behalf.
What Part B Covers
Part B is medical insurance, covering two broad categories: medically necessary services and preventive services. Medically necessary services include anything that meets accepted standards of medical practice to diagnose or treat a condition. Preventive services are designed to catch illness early or prevent it altogether.
The outpatient and doctor-visit side of Medicare is extensive. Part B pays for:
- Doctor and specialist visits: Office visits, second opinions, and outpatient procedures.
- Preventive screenings: Annual depression screenings, flu shots, cancer screenings, and other wellness checks. You pay nothing for most preventive services when your provider accepts Medicare’s payment terms.
- Mental health care: Individual and group psychotherapy, partial hospitalization programs, and substance use disorder treatment are all covered as outpatient services.
- Ambulance services: When medically necessary transport is required.
- Durable medical equipment: Wheelchairs, walkers, hospital beds, oxygen equipment, CPAP machines, blood sugar monitors and test strips, crutches, canes, and infusion pumps, among others.
- Limited outpatient prescription drugs: Most prescriptions fall under Part D, but Part B covers certain drugs administered in a clinical setting.
- Clinical research: Costs related to qualifying clinical trials.
Blood received as a hospital outpatient falls under Part B rather than Part A. The same 3-unit rule applies: you cover the first 3 units per year. After meeting your Part B deductible, you pay a copayment for blood processing and handling that varies by situation.
What Original Medicare Does Not Cover
Several common healthcare needs fall outside both Part A and Part B. The gaps that catch people off guard most often are dental care, vision, hearing, and long-term care. Original Medicare does not cover routine dental cleanings, fillings, tooth extractions, or dentures. Eye exams for prescription glasses aren’t covered. Hearing aids and the exams needed to fit them are excluded. And long-term custodial care, like an extended stay in a nursing home when you don’t need skilled medical treatment, is not covered at all.
Many people fill these gaps with a Medicare Supplement (Medigap) plan, a Medicare Advantage plan, or standalone dental and vision policies.
What Part A Costs in 2025
Most people pay no monthly premium for Part A because they or a spouse paid Medicare taxes for at least 10 years (40 quarters) while working. If you had 30 to 39 quarters of coverage, the reduced premium is $285 per month in 2025. With fewer than 30 quarters, the full premium is $518 per month.
Even with premium-free Part A, you still face a deductible and coinsurance for hospital stays. The inpatient hospital deductible is $1,676 per benefit period in 2025. That covers the first 60 days. For days 61 through 90, you pay $419 per day in coinsurance. If your stay extends beyond 90 days, you draw from a limited pool of “lifetime reserve days” at $838 per day.
For skilled nursing facility stays, the first 20 days are fully covered after the Part A deductible. Days 21 through 100 require a daily coinsurance of $209.50 in 2025. After day 100, Medicare stops paying entirely.
What Part B Costs in 2025
The standard Part B monthly premium is $185.00 in 2025. Unlike Part A, nearly everyone pays this premium because it’s deducted directly from Social Security checks. Higher-income enrollees pay more through income-related surcharges.
The annual Part B deductible is $257 in 2025. Once you’ve met it, the standard cost-sharing is 20% of the Medicare-approved amount for most services. If you receive outpatient care at a hospital clinic or outpatient department, you may owe an additional copayment to the facility on top of that 20%.
When to Enroll
Your initial enrollment period is a 7-month window surrounding your 65th birthday. Signing up during this window carries no penalties. If you miss it and don’t have qualifying coverage through an employer, you can enroll during the general enrollment period between January 1 and March 31 each year, but late enrollment typically results in a lifelong premium penalty. For Part B, that penalty adds 10% to your monthly premium for every full 12-month period you could have had coverage but didn’t.
If you’re still working and covered by an employer plan at 65, you generally won’t face a penalty as long as you enroll within 8 months of leaving that job or losing that coverage.