The alphabet, decoded
Part A vs. Part B: the line between them decides who bills you
Short answer: Part A is hospital insurance (inpatient stays, skilled nursing, hospice, some home health) and is premium-free for most people. Part B is medical insurance (doctors, outpatient care, tests, equipment) and costs $202.90 a month in 2026. The tricky part is the borderline: the same building can bill under either part depending on your status, and the difference is real money.
Key takeaways
- Part A covers inpatient hospital care, skilled nursing after a qualifying stay, hospice, and some home health; premium-free with about 10 years of covered work.
- Part B covers doctors, outpatient care, preventive services, lab tests, and durable medical equipment; $202.90/month in 2026.
- Part A’s deductible is $1,736 per benefit period (not per year); Part B’s is $283 per year, then 20% coinsurance with no cap.
- The same hospital visit can bill under A (inpatient) or B (observation/outpatient); the status question matters.
- Without about 10 years of Medicare-taxed work, Part A costs $311 or $565 a month in 2026 depending on quarters worked.
The clean split
| Part A: hospital insurance | Part B: medical insurance | |
|---|---|---|
| Covers | Inpatient hospital stays, skilled nursing facility care after a qualifying stay, hospice, some home health | Doctor visits, outpatient care, preventive services, lab tests, imaging, ambulance, durable medical equipment, many office-administered drugs |
| 2026 premium | $0 for most (about 10 years of covered work); otherwise $311 (30–39 quarters) or $565 (under 30) | $202.90/month standard; $284.10–$689.90 with IRMAA |
| Deductible | $1,736 per benefit period | $283 per year |
| After deductible | Daily coinsurance kicks in for long stays ($434/day, days 61–90) | Medicare pays 80%, you pay 20%, with no annual cap |
| The gap a supplement fixes | Long-stay coinsurance | The uncapped 20% |
2026 amounts per the CMS premiums and deductibles announcement; Part A buy-in rates apply only to those without sufficient work history.
Two structural quirks worth internalizing. Part A’s deductible is per benefit period, not per year: a benefit period starts at admission and ends after 60 days without inpatient or skilled care, so two hospitalizations months apart can mean two $1,736 deductibles in one calendar year. And Part B’s 20% has no ceiling: on a $200,000 outpatient cancer year, 20% is $40,000, which is the single number that makes Medigap or an Advantage out-of-pocket max non-optional for most people.
The borderline cases that decide your bill
- Hospital "observation status." A night in a hospital bed under observation is outpatient: Part B, not Part A, and it doesn’t count toward the 3-day inpatient stay that qualifies you for skilled nursing coverage. Ask, every admission: "inpatient or observation?"
- Drugs. Pharmacy prescriptions are Part D. Drugs administered in a doctor’s office or infusion center (many cancer treatments, injections) are Part B. Same molecule, different part, different math.
- Surgery. Inpatient surgery bills under A; the same procedure done outpatient (increasingly common) bills under B, with the 20% applying.
- Home health. Can bill under either depending on circumstances; from your side it works the same: covered skilled visits at $0.
What neither part covers
The famous exclusions live outside both: routine dental, routine vision, hearing aids, and long-term custodial care. Prescription drugs from a pharmacy need Part D. The gap-by-gap map is in our what-Medicare-doesn’t-cover article.
Enrolling: usually together, occasionally apart
Most people take A and B together in their 7-month window at 65 (via ssa.gov/medicare). The main reasons they separate: workers at 20+ employers often take free Part A while delaying Part B (unless HSA contributions argue for delaying both), and people receiving Social Security get both automatically and must actively decline B if they have qualifying coverage. The decision trees live in the working-past-65 guide and the HSA article.
Questions people also ask
What is the difference between Medicare Part A and Part B?
Is Medicare Part A really free?
Do I need Part B if I have Part A?
Why did my hospital stay bill under Part B?
Does Part A or Part B cover surgery?
Sources for this article
- CMS.gov2026 Medicare Parts A & B Premiums and Deductibles: every premium, deductible, and coinsurance figure here.
- SSA.govSign up for Medicare: enrollment mechanics for both parts.
- Medicare.govCoverage lookup: which part covers a specific service.
Figures checked against these sources in August 2026. We update within weeks when CMS publishes new amounts.
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