It refers to the two-part federal health insurance program for people 65 and older (and some younger adults with disabilities): Medicare Part A (Hospital Insurance), which handles inpatient costs like hospital stays and skilled nursing care, and Medicare Part B (Medical Insurance), which covers outpatient care such as doctor visits and preventive screenings. Together, Original Medicare forms the foundation of your coverage, and every supplemental decision flows from how these two halves work.
Below is a walkthrough of each part, the dollar amounts attached, the gaps that bite hardest, and the next step that fits your situation.
The Two Halves of Original Medicare
Two programs, not one, sit inside Original Medicare, and the Centers for Medicare & Medicaid Services runs them together as a package. The split exists because inpatient and outpatient care follow such different cost patterns that bundling them under one premium would create odd incentives and confusing bills.
Part A: Hospital Insurance
Formal admission to a hospital triggers Part A, as does time in a skilled nursing facility following a qualifying inpatient stay, hospice care for a terminal illness, or certain limited home health services. Think of Part A as the side of Medicare that kicks in when a health event forces an inpatient setting.
Part B: Medical Insurance
Doctor appointments, outpatient procedures, lab work, imaging, mental health services, durable medical equipment such as wheelchairs and oxygen, and a wide range of preventive screenings all fall under Part B for care that does not require an overnight stay. If Part A is the emergency side, Part B is the maintenance side, built to catch problems early and manage chronic conditions.
| Coverage Area | Part A | Part B |
|---|---|---|
| Hospital inpatient stays | Covered | Not covered |
| Skilled nursing facility (post-hospital) | Covered (limited) | Not covered |
| Hospice care | Covered | Not covered |
| Doctor visits | Not covered | Covered |
| Outpatient care and labs | Not covered | Covered |
| Preventive screenings | Not covered | Covered at no cost |
| Durable medical equipment | Not covered | Covered (80% after deductible) |
You can use Original Medicare at any doctor or hospital in the United States that accepts Medicare, which most do. No network restrictions, no referrals required for specialists, and no prior authorization for most services. That freedom is one of the most concrete reasons people stay with Original Medicare rather than switching to a private plan.
With that freedom established, it helps to see exactly what Part A picks up before a hospital bill does.
What Part A Covers and What a Hospital Stay Actually Costs
Part A’s coverage looks generous until you see the cost-sharing attached. Each benefit period begins the day you’re admitted and ends after 60 consecutive days without inpatient care, and it carries a deductible that resets every time you re-enter the hospital after a 60-day gap. For 2025, that deductible is $1,676 per benefit period.
Inpatient Hospital Stays
After you meet the deductible, Part A covers the full cost of your first 60 days in the hospital per benefit period. Days 61 through 90 carry a daily coinsurance of $419 in 2025, and once you exceed 90 days, you dip into your 60 lifetime reserve days, each of which carries an $838 coinsurance in 2025. Those reserve days don’t reset, so using them reduces what you have left for future catastrophic stays.
Skilled Nursing Facility Care
A qualifying three-day inpatient hospital stay unlocks full Part A coverage of skilled nursing facility care for the first 20 days. Days 21 through 100 require a daily coinsurance of $209.75 in 2025. Day 101 and beyond falls entirely on your shoulders, and this is one of the most common surprises for families who assumed Medicare would keep paying.
Who Pays Nothing for Part A
Most people pay no monthly premium for Part A, provided they or a spouse worked and paid Medicare taxes for at least 10 years (40 quarters). If you don’t meet that threshold, you can still buy Part A, with premiums up to $518 per month in 2025, depending on how many quarters you did work.
Once inpatient costs are clear, the outpatient side works differently enough to deserve its own walkthrough.
Skilled nursing coverage is not the same as long-term custodial care. Medicare pays for skilled nursing only after a hospital stay and only when the daily care requires licensed nurses or therapists.
What Part B Covers and What an Outpatient Visit Actually Costs
Part B runs on a different cost structure than Part A. Instead of a per-benefit-period deductible, you pay an annual deductible ($257 in 2025), and then a standard 20% coinsurance applies to most covered services, with no annual out-of-pocket maximum. That missing cap is the single biggest financial risk in Original Medicare.
Doctor Visits, Outpatient Care, and Equipment
Every doctor visit with a provider who accepts Medicare, every outpatient service from same-day surgery to a diagnostic colonoscopy, every lab test ordered, and every piece of durable medical equipment prescribed is billed through Part B. The 20% coinsurance applies after the annual deductible, and there’s no ceiling on how high that 20% can climb in a bad year.
Preventive Services at No Cost
Providers who accept assignment agree to take Medicare’s approved amount as full payment, and in exchange Part B covers a long list of preventive services at zero cost to the patient. That list includes annual wellness visits, flu shots, pneumonia vaccines, mammograms, Pap smears, colonoscopies, diabetes screenings, cardiovascular screenings, and more. Catching problems early is the cheapest way to use the system, and these services are the one area where the math genuinely works in your favor.
Part B Premiums
$185 per month is the standard Part B premium set for 2025. Higher-income beneficiaries pay more through income-related monthly adjustment amounts (IRMAA), with surcharges that can push the premium above $600 per month for the top income bracket. Lower-income beneficiaries may qualify for state Medicaid programs that pay the Part B premium on their behalf.
Those premiums pay for a defined set of benefits, and the boundaries of that set shape what you’ll need to arrange elsewhere.
The Services Original Medicare Does Not Cover
Original Medicare’s exclusions are consistent enough to plan around, and they’re the reason supplemental coverage matters. Four categories account for most out-of-pocket surprises.
Dental Care
Routine cleanings, fillings, extractions, root canals, crowns, and most dentures fall outside Medicare’s scope. The narrow exception covers certain dental procedures when they’re medically necessary as part of a covered medical procedure, such as a tooth extraction required before jaw radiation or a dental exam before an organ transplant.
Vision Care
Routine eye exams, eyeglasses, and contact lenses are excluded. The one exception is a single pair of eyeglasses or contact lenses after cataract surgery that implants an intraocular lens.
Hearing Care
Hearing aids and the exams to fit them are excluded entirely, which is a serious gap because hearing aids commonly cost several thousand dollars per pair. Original Medicare contributes nothing toward the device, the fitting, or the follow-up adjustments.
Long-Term and Overseas Care
Custodial care, the kind of help with daily activities like bathing, dressing, and eating that doesn’t require skilled nursing, is excluded whether delivered at home or in a nursing facility. Care received outside the United States is also excluded, except in rare emergencies near U.S. borders or during a cruise ship voyage within six hours of a U.S. port.
Where Prescriptions, Dental, Vision, and Hearing Coverage Actually Come From
Because Original Medicare leaves these gaps, your next move is choosing how to close them. Three paths exist, and the right one depends on how you use healthcare.
Adding a Part D Drug Plan
Outpatient prescription drugs are not included in Original Medicare at all. You add them through a standalone Medicare Part D plan, sold by private insurers with their own formularies, premiums, and pharmacy networks. Part D plans vary widely in which drugs they cover and what they charge, so checking your specific medications against each plan’s formulary is essential before enrolling.
Switching to Medicare Advantage
Private Medicare Advantage (Part C) plans fold Part A, Part B, and usually Part D into a single package, frequently layering on extras such as routine dental, vision, hearing, fitness benefits, and an annual out-of-pocket maximum that Original Medicare lacks. The trade-off is network restrictions, prior authorization requirements, and the fact that you’re no longer using Original Medicare at all; you’re in a private plan that administers your Medicare benefits.
Adding Medigap Supplemental Insurance
Medigap policies are sold by private insurers to fill the cost-sharing gaps in Original Medicare, such as the Part A deductible, the Part B coinsurance, and skilled nursing coinsurance. Medigap does not add new benefits like dental or drug coverage. If you want drug coverage, you pair Medigap with a standalone Part D plan.
| Option | Adds Drug Coverage | Adds Dental/Vision/Hearing | Has Out-of-Pocket Maximum |
|---|---|---|---|
| Standalone Part D | Yes | No | No (catastrophic cap only) |
| Medicare Advantage | Usually | Often | Yes (plan-set limit) |
| Medigap + Part D | Yes (via Part D) | No | Effectively (low cost-sharing) |
Common Coverage Gaps, Late-Enrollment Penalties, and Smart Next Steps
The most expensive mistakes with Medicare usually come from misunderstanding enrollment timing rather than from coverage itself. Three rules account for most of those mistakes.
The Late-Enrollment Penalty
If you delay enrolling in Part B or Part D without qualifying employer coverage (your own or your spouse’s active employment-based group health plan), you trigger a permanent premium penalty. The Part B penalty adds 10% to your premium for each full 12 months you delayed, and it stays with you for as long as you have Part B.
The Part D penalty is calculated differently, at 1% of the national base premium per month without creditable coverage, also permanent.
What Counts as Creditable Coverage
Neither COBRA continuation coverage nor ACA marketplace plans count as creditable coverage for Medicare purposes. Many people assume they’re protected and discover the gap only when a penalty notice arrives. If you have employer coverage, confirm with the employer’s benefits office that the plan is creditable for both Part B and Part D before deciding to delay enrollment.
Matching Your Choice to Your Situation
Original Medicare plus Medigap suits you if you travel frequently, see many specialists across state lines, want predictable costs, and value the freedom to see any provider that accepts Medicare. Medicare Advantage suits you if you prefer bundled extras, are comfortable staying within a plan’s network, and want a hard annual cap on out-of-pocket spending.
The best choice depends on your doctors, your medications, your travel patterns, and your tolerance for network rules. Your next step should start there.
- Turning 65 with retiree coverage: Enroll in Part A and Part B, then add a Part D plan or switch to Medicare Advantage.
- Still working past 65 with employer coverage: Delay Part B (and possibly Part A) until employment ends, but confirm the plan is creditable first.
- On Social Security disability for 24 months: You’re automatically enrolled in Original Medicare; add Part D or switch to Medicare Advantage during your Initial Enrollment Period.
- Leaving employer or COBRA coverage: Use a Special Enrollment Period (eight months for Part B, two months for Part D) to avoid penalties.
- Already on Original Medicare: Review your Part D plan each fall during the Annual Election Period (October 15 to December 7) because formularies, premiums, and pharmacy networks change yearly.
Bottom Line
Original Medicare covers the big stuff: hospital stays, doctor visits, outpatient care, and prevention. It leaves the routine stuff, like dental, vision, hearing, drugs, and long-term care, to you or to a supplemental plan. Knowing exactly which half pays for what, and which half hands you the bill, is the foundation for every decision that follows.
FAQ
What does Medicare Part A cover?
Part A covers inpatient hospital care, skilled nursing facility care after a qualifying hospital stay, hospice care for terminal illness, and limited home health services. Most people pay no monthly premium for Part A if they or a spouse paid Medicare taxes for at least 10 years.
What does Medicare Part B cover?
Part B covers doctor visits, outpatient procedures, lab tests, imaging, durable medical equipment, mental health services, and a wide range of preventive screenings such as flu shots, mammograms, and the annual wellness visit, all at no cost when a provider accepts assignment.
Is preventive care covered by Medicare?
Yes. Part B covers many preventive services at zero out-of-pocket cost when delivered by a provider who accepts assignment, including annual wellness visits, flu and pneumonia vaccines, mammograms, colonoscopies, diabetes screenings, and cardiovascular screenings.
What is not covered by basic Medicare?
Original Medicare does not cover routine dental care, vision exams and eyeglasses, hearing aids and fitting exams, long-term custodial care, outpatient prescription drugs, or care received outside the United States (with rare exceptions near U.S. borders).
Do I need supplemental insurance with basic Medicare?
Most people do. Without supplemental coverage, you’re exposed to the Part A deductible per benefit period, 20% Part B coinsurance with no annual cap, and all excluded services like dental and drugs. A Part D plan, Medigap policy, or Medicare Advantage plan can close most of those gaps.
How much does basic Medicare cost?
Most people pay $0 for Part A. The standard Part B premium is $185 per month in 2025, plus a $257 annual deductible and typically 20% coinsurance on covered services. Higher-income beneficiaries pay income-adjusted premiums, and adding Part D or Medigap adds separate premiums.
