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Medicare guide · Original Medicare · 13 min read

Original Medicare — what Parts A and B actually cover.

Original Medicare is the federal health insurance program for people 65+ (and certain younger people with disabilities). It has two parts: Part A covers hospital and inpatient care; Part B covers doctor visits and outpatient care. Together they're the foundation of every Medicare coverage strategy — Part C (Medicare Advantage) replaces them; Part D and Medigap supplement them. Here's exactly what they do, what they cost, and where the gaps are.

Part A — Hospital insurance

Inpatient care, mostly

What happens when you're admitted to a hospital, transferred to rehab, or going on hospice.

What Part A covers
  • · Inpatient hospital stays (including semi-private room, meals, nursing)
  • · Skilled nursing facility (SNF) care for up to 100 days following a 3-day inpatient stay
  • · Hospice care (terminal illness, life expectancy ≤ 6 months)
  • · Some home health care after hospitalization
  • · Inpatient mental health care (190-day lifetime limit at psychiatric hospitals)
What Part A costs in 2026
  • Premium: $0 if you or your spouse paid Medicare taxes for 40+ quarters (10+ years). Otherwise $285-$518/month.
  • Deductible: $1,676 per benefit period (a benefit period restarts after 60 days without inpatient care).
  • Days 61-90 of a hospital stay: $419/day coinsurance.
  • Days 91+ (lifetime reserve days): $838/day, max 60 days over your lifetime.
  • Beyond reserve days: you pay 100% of cost.
  • SNF days 21-100: $209.50/day coinsurance.
Part B — Medical insurance

Everything else medical

Doctor visits, outpatient services, durable medical equipment, preventive care, and most everything that isn't hospital admission.

What Part B covers
  • · Doctor visits (primary care + specialists)
  • · Outpatient hospital services
  • · Lab tests, X-rays, MRIs, CT scans
  • · Durable medical equipment (walkers, oxygen, wheelchairs)
  • · Preventive services (annual wellness visit, screenings, vaccines including COVID, flu, RSV)
  • · Mental health (outpatient counseling, psychiatry)
  • · Ambulance transport (when medically necessary)
  • · Some home health, physical therapy, occupational therapy
  • · Limited prescription drugs (chemotherapy, dialysis meds — most drugs are Part D)
What Part B costs in 2026
  • Premium: $202.90/month standard. Higher for incomes above $106k single / $212k joint (IRMAA — see below).
  • Deductible: $257 per calendar year.
  • Coinsurance: after the deductible, you pay 20% of the Medicare-approved amount for most services. Medicare pays 80%. No annual cap on what you can owe in 20%.

IRMAA — the income surcharge on Part B

If your modified adjusted gross income (MAGI) two years ago was above the threshold, you pay more than the standard $202.90/month for Part B. Same applies to Part D. The 2026 brackets:

Single MAGIJoint MAGIPart B premiumPart D surcharge
≤ $106,000≤ $212,000$202.90$0
$106,001-$133,000$212,001-$266,000$284.10$13.70
$133,001-$167,000$266,001-$334,000$405.40$35.40
$167,001-$200,000$334,001-$400,000$526.70$57.00
$200,001-$500,000$400,001-$750,000$648.00$78.60
> $500,000> $750,000$688.40$85.80

If your income just dropped: Recently retired? File form SSA-44 to appeal IRMAA. Our comparison tool flags this opportunity automatically and shows the dollars you'd save.

What Original Medicare does NOT cover

The gaps. Some are filled by Medigap (the standardized supplement plans F, G, N, K, L); others require separate insurance or out-of-pocket spending.

The Two-Midnight Rule

One subtle rule that catches a lot of people: whether your hospital stay counts as inpatient (Part A) or outpatient observation (Part B) depends on whether your physician expected you to stay at least two midnights.

Why it matters: if you go to the hospital, ask explicitly whether you're admitted as inpatient or under observation. Observation status can mean the SNF you need afterward isn't covered, even though you spent four nights in the hospital. The distinction is between which Medicare part pays — Part A vs Part B — and it has real cost consequences.

How to enroll in Original Medicare

If you're already collecting Social Security retirement benefits when you turn 65, you're auto-enrolled in Parts A and B. If you're not yet collecting SS, you have to actively enroll. Three windows:

Full enrollment-windows breakdown: Medicare Enrollment Windows guide. Working past 65? Working Past 65 guide covers the deferral rules and creditable-coverage requirements.

Original Medicare alone has gaps. Your next decisions:

Add Medigap and Part D, or replace with Medicare Advantage?

Once you have Original Medicare, you choose between supplementing it (Medigap + Part D) and replacing it (Medicare Advantage / Part C). The math depends on your medications, doctors, and how much network flexibility matters to you.

Medigap vs Medicare AdvantagePart C vs Part D
Run the math

Our $49 tool ranks every Plan G + Part D combo against the best Medicare Advantage plan in your county for your medications.

Compare for $49
Sources
· CMS — Medicare & You handbook 2026
· CMS — 2026 Medicare Parts A & B Premiums and Deductibles fact sheet
· CMS — Two-Midnight Rule Fact Sheet (updated 03/12/2026)
· SSA — Medicare enrollment via ssa.gov/medicare and Form CMS-L564