Your First Year on Medicare: What Parts A, B, C, and D Mean for Your Care

Why Medicare Is Divided Into Parts

When people first hear that Medicare has "parts," the natural reaction is confusion — even mild panic. Why isn't it just one plan? The short answer is history. Medicare was created in 1965 to cover hospital care and doctor visits for Americans 65 and older. Over decades, Congress added prescription drug coverage and later allowed private insurers to offer bundled alternatives. Each addition became its own "part," and that alphabet-soup structure has stuck.

Think of it this way: the parts are less like separate insurance products and more like modular building blocks. You combine them to construct the coverage that fits your life. A healthy 65-year-old who takes no medications might start with just Parts A and B. Someone managing diabetes and heart disease will almost certainly want to add Part D — and possibly Part C — to keep costs predictable.

Before you can make smart choices, you need to understand what each part does, what it costs, and — crucially — how the pieces interact. See our detailed breakdown of all four Medicare parts for a side-by-side look at coverage specifics. For now, let's walk through each part methodically, starting at the beginning.

Part A: Your Hospital Coverage

Part A is Medicare's foundation. It covers inpatient care — meaning care you receive when you are formally admitted to a hospital, skilled nursing facility, or inpatient rehabilitation center. It also covers hospice care and some limited home health services.

What Part A actually pays for

• Inpatient hospital stays — room, meals, nursing services, and most medications administered during your stay
• Skilled nursing facility (SNF) care — but only after a qualifying hospital stay of at least 3 days, and only for medically necessary skilled care (physical therapy, wound care, IV medications)
• Home health care — part-time skilled nursing or therapy ordered by your doctor
• Hospice care — for terminal illness when curative treatment has stopped

What Part A costs

Here's welcome news: most people pay no monthly premium for Part A. If you or your spouse paid Medicare taxes for at least 10 years (40 quarters) while working, you've already earned premium-free Part A. Those who haven't met that threshold can still buy Part A, but the 2024 premium runs up to $505 per month — a significant cost worth checking before you assume you qualify for free coverage.

Even with premium-free Part A, you're not off the hook for all costs. Part A has a deductible per benefit period (not per year), which in 2024 is $1,632. After that deductible, you pay nothing for the first 60 days of an inpatient stay. Days 61–90 carry a daily coinsurance charge. Beyond 90 days, you draw on a limited pool of "lifetime reserve days" — and after those run out, you pay the full cost. These deductible and cost-sharing structures can add up quickly during a long hospitalization.

When Part A starts

If you're already receiving Social Security benefits when you turn 65, you're enrolled in Part A automatically. If not, you need to sign up actively during your Initial Enrollment Period — the 7-month window centered on your 65th birthday month.

Part B: Your Outpatient and Medical Coverage

If Part A keeps you covered when you're admitted to a hospital, Part B handles nearly everything else — the doctor visits, lab work, imaging, outpatient procedures, and preventive screenings that make up the bulk of most people's annual health care interactions.

What Part B covers

• Doctor visits — primary care and specialist appointments
• Outpatient surgery and procedures — when you don't need an overnight hospital admission
• Preventive care — annual wellness visits, flu shots, mammograms, colonoscopies, and more, often at no cost to you
• Durable medical equipment (DME) — wheelchairs, walkers, CPAP machines, blood sugar monitors
• Outpatient mental health care
• Some home health services and certain drugs administered in a doctor's office (like chemotherapy infusions)

You can see the full list of covered services at Medicare.gov, but the key principle is this: if a service is medically necessary and performed outside a hospital inpatient stay, Part B is likely involved. For a broader look at what typical health plans include, see our guide on what's covered under health insurance.

What Part B costs

Unlike Part A, Part B always has a monthly premium. The standard premium in 2024 is $174.70 per month. Higher earners pay more under an adjustment called IRMAA (Income-Related Monthly Adjustment Amount) — so if your income from two years ago exceeded certain thresholds, expect a higher bill.

Part B also has an annual deductible ($240 in 2024). After you meet it, Medicare pays 80% of approved costs and you pay the remaining 20%. That 20% has no cap — a fact that surprises many new beneficiaries. A $50,000 cancer treatment means a $10,000 out-of-pocket bill under Part B alone. This is precisely why many people add a Medigap (Medicare Supplement) policy to cover that 20%.

Avoiding the Part B late-enrollment penalty

If you delay Part B past your Initial Enrollment Period without qualifying employer coverage, you'll pay a 10% penalty on your premium for every 12-month period you were eligible but didn't enroll. That surcharge is permanent — it follows you for as long as you have Part B. The penalty applies even if you only delayed by a few months past the window. See our pre-enrollment checklist to make sure you're timing your sign-up correctly.

Part C: Medicare Advantage — an Alternative Way to Get Coverage

Part C, officially called Medicare Advantage, is not an add-on to Original Medicare — it's an alternative delivery system. When you enroll in a Medicare Advantage plan, a Medicare-approved private insurer takes over the administration of your Parts A and B benefits. Medicare pays that insurer a set amount each month; the insurer then covers your care according to their plan's rules.

What Medicare Advantage typically includes

• All Part A and Part B benefits (required by law)
• An annual out-of-pocket maximum — something Original Medicare lacks
• Often: Part D drug coverage bundled in (called MA-PD plans)
• Frequently: extra benefits Original Medicare doesn't cover — dental cleanings, eyeglasses, hearing aids, gym memberships, over-the-counter allowances

The trade-off: networks and referrals

Medicare Advantage plans nearly always use provider networks — HMOs, PPOs, or similar structures. An HMO-style plan typically requires you to choose a primary care physician and get referrals to see specialists. A PPO-style plan gives more flexibility but still charges more when you go out of network. If you live in a rural area with fewer participating providers, or if you travel frequently and want to see doctors anywhere, this network restriction can be a real limitation.

The cost picture is also more nuanced than it first appears. Many Medicare Advantage plans advertise $0 premiums, which sounds appealing — but you still pay your Part B premium. And some plans have higher copays or narrower formularies than you might expect. Digging into the plan's Evidence of Coverage document before you enroll is essential.

Deciding between Original Medicare and Medicare Advantage is the most consequential choice you'll make in your first year. Our article on Original Medicare vs. Medicare Advantage walks through that comparison in depth.

Part D: Prescription Drug Coverage

Original Medicare — Parts A and B alone — does not cover the vast majority of drugs you pick up at a pharmacy. That gap is filled by Part D, which was added to Medicare in 2006 under the Medicare Modernization Act. Part D plans are offered by private insurers approved by Medicare, and they work through a system of drug lists called formularies.

How Part D plans work

Each Part D plan has its own formulary — a tiered list of covered drugs. Generics sit on lower tiers with lower copays. Brand-name and specialty drugs land on higher tiers with higher cost-sharing. Not all plans cover the same drugs, so if you take specific medications, you must check each plan's formulary before enrolling. Medicare's Plan Finder tool at medicare.gov allows you to enter your medications and compare real costs across available plans in your ZIP code.

Part D costs to understand

The late-enrollment penalty — and why it matters

If you don't enroll in a Part D plan when you're first eligible, and you go 63 or more consecutive days without creditable drug coverage (coverage at least as good as standard Part D), you'll owe a permanent late-enrollment penalty. That penalty is 1% of the national base beneficiary premium multiplied by the number of months you went without coverage — and it stays on your premium for life. Even if you're currently healthy and take no medications, enrolling in a low-cost Part D plan protects you from this risk.

For a deeper look at how Part D formularies, tiers, and cost-sharing interact with your specific drug needs, see what each Medicare part actually covers. And for help decoding terms like "formulary," "tier," and "cost-sharing," our Medicare glossary breaks it all down plainly.

How the Parts Fit Together — and What to Do Next

Let's step back and look at the full picture. You essentially have two paths in Medicare:

Path 1: Original Medicare (Parts A + B) with optional add-ons

1. Enroll in Part A (hospital coverage — likely free)
2. Enroll in Part B (outpatient coverage — monthly premium applies)
3. Add a Medigap/Medicare Supplement plan to cover the 20% Part B gap and other cost-sharing (optional but widely recommended)
4. Add a standalone Part D plan for prescription drugs

Path 2: Medicare Advantage (Part C)

1. Enroll in Part A and Part B (still required)
2. Choose a Part C (Medicare Advantage) plan from a private insurer
3. Most MA plans bundle Part D drug coverage — check whether yours does
4. You generally cannot also hold a Medigap plan while on Medicare Advantage

A quick summary of your choices

Your next step is to think about what matters most to you: freedom to see any doctor, predictable monthly costs, extra benefits, or minimal paperwork. Once you know your priorities, you're ready to compare specific plans in your area. Our pre-enrollment questions guide gives you a structured checklist to work through before you commit. And if you want a direct comparison of Original Medicare versus Advantage plans, start with our comparison guide.

Medicare doesn't have to be overwhelming. When you see each part for what it actually does — hospital, outpatient, bundled alternative, drugs — the decisions become much more manageable. Take it one piece at a time, and you'll build the coverage that works for your life.