Medicare Made Simple: Parts A, B, C, and D Explained

Medicare is one of those topics that sounds straightforward until you actually try to sign up for it. Then you realize there are four parts, two main tracks, dozens of plan options in your area, and a deadline you might not even know about.

That's where most of the confusion starts. Not with the coverage itself, but with the structure.

This article walks through what each part of Medicare covers, what it costs, and how the pieces fit together. Once you understand what the four parts actually do, the bigger decision — which coverage path is right for you — becomes a lot clearer.

Start Here: Medicare Has Two Tracks

Before getting into the individual parts, it helps to know that Medicare is organized around two main ways to receive your coverage.

Original Medicare is run directly by the federal government. You enroll in Part A and Part B separately, and you can add a standalone Part D plan for prescriptions. Most doctors and hospitals in the country accept it.

Medicare Advantage (Part C) is an alternative. Instead of Original Medicare, you enroll in a private insurance plan that bundles your hospital, medical, and usually prescription coverage together. These plans operate within Medicare's rules, but they're run by private insurers.

You pick one track or the other. You can't have both at the same time.

Part A: Hospital Coverage

Part A covers inpatient hospital stays. If you're admitted to a hospital, Part A is what pays for the room, nursing care, meals, and most services during your stay.

It also covers:

• Skilled nursing facility care (after a qualifying hospital stay of at least 3 days)
• Hospice care
• Some home health services

What Part A costs: Most people pay $0 in monthly premiums for Part A, because they or their spouse worked and paid Medicare taxes for at least 10 years (40 quarters). If you don't meet that threshold, you can still buy into Part A. In 2025, the premium for someone with fewer than 30 quarters of work history is $505 per month.

Even with $0 in premiums, Part A has a deductible. In 2025, that's $1,632 per hospital benefit period, not per year. A benefit period begins when you're admitted and ends when you've been out of the hospital for 60 consecutive days. If you're readmitted after that window, a new deductible applies.

The official source for current Part A costs isMedicare.gov, which the government updates each year.

Part B: Medical Coverage

Part B covers outpatient medical care — everything that happens outside the hospital.

That includes:

• Doctor visits and specialist appointments
• Lab tests and X-rays
• Preventive screenings (many are covered at no cost to you)
• Durable medical equipment, like wheelchairs or walkers
• Outpatient surgeries and procedures
• Mental health services

What Part B costs: In 2025, the standard monthly premium for Part B is $185. Most people pay this amount, though higher-income individuals pay more through a surcharge called IRMAA (Income-Related Monthly Adjustment Amount). If your income from two years ago was above $106,000 for an individual or $212,000 for a couple, your premium is higher.

Part B also has an annual deductible of $257 in 2025. After that, Medicare covers 80% of approved costs, and you're responsible for the remaining 20%. There's no out-of-pocket cap on that 20% under Original Medicare, which is one reason many people add a Medigap supplement policy.

Part C: Medicare Advantage

Medicare Advantage is the private insurance alternative to Original Medicare. These plans are sold by private insurers, approved by Medicare, and required to cover at least everything Parts A and B cover. Most also include prescription drug coverage (Part D) and extras like dental, vision, and hearing.

What Part C costs: Premiums vary widely by plan and location. Some plans advertise $0 premiums, though you still pay your Part B premium. Others charge an additional monthly amount. The tradeoff is that Advantage plans typically have lower upfront costs but more structured networks. You may need referrals to see specialists, and coverage is generally limited to the plan's provider network.

Medicare Advantage enrollment has grown steadily. As of 2024, more than 54% of Medicare-eligible people were enrolled in an Advantage plan.

Whether Advantage or Original Medicare is the better fit depends on where you live, how often you travel, how many doctors you see regularly, and your health needs. There's no universal right answer.

Part D: Prescription Drug Coverage

Part D covers prescription medications. If you're on Original Medicare, you add a standalone Part D plan from a private insurer. If you're on Medicare Advantage, your drug coverage is usually already bundled in.

What Part D costs: Monthly premiums vary by plan. The average basic premium in 2025 is around $46 per month, though plans range from under $10 to over $100. Each plan has its own formulary — the list of drugs it covers — and its own cost-sharing structure.

Starting in 2025, a significant change took effect: the Medicare Part D out-of-pocket cap was set at $2,000 per year. That's the most you'll pay for covered prescription drugs in a calendar year, regardless of how expensive your medications are.

TheMedicare Plan Finder at Medicare.govis the best free tool for comparing Part D and Medicare Advantage plans in your specific zip code. It's updated each year during open enrollment, which runs October 15 through December 7.

What's Not Covered

Original Medicare does not cover routine dental, vision, or hearing care. It also doesn't cover long-term custodial care — help with daily activities like bathing or dressing in a nursing home setting.

Some Medicare Advantage plans do offer limited dental, vision, and hearing benefits, which is one reason people choose that path. But the coverage varies significantly by plan.

When You Need to Sign Up

Medicare enrollment has specific windows, and missing them can mean permanent late enrollment penalties.

Your Initial Enrollment Period is a 7-month window that starts 3 months before the month you turn 65, includes your birthday month, and extends 3 months after. If you're still working and covered by an employer plan, you may be able to delay enrollment without penalty — but the rules depend on how many people work at your employer.

The Social Security Administration handles Medicare enrollment for most people. You can learn more or sign up atSSA.gov orMedicare.gov.

The Honest Summary

Medicare's four parts aren't complicated once you separate them out. Part A is the hospital. Part B is the doctor. Part C is the private plan alternative. Part D is prescriptions.

The real decision comes after: Original Medicare or Medicare Advantage, and which specific plans make sense for your situation, your doctors, and your prescriptions. That's where the details matter, and that's where the next step in your Medicare planning begins.