Key Takeaways
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Medicare has four basic parts, but combining them into complete, usable coverage is where most people struggle. The gaps, overlaps, and additional choices make it far more complicated than it appears on paper.
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Understanding enrollment timelines, coordination with supplemental coverage, and cost-sharing rules can prevent unexpected bills and lifelong penalties.
Medicare’s Four-Part Structure Isn’t as Straightforward as It Looks
At first glance, Medicare seems neatly packaged. Four parts: A, B, C, and D. But once you start making real-world decisions, it quickly becomes clear that these parts don’t snap together like puzzle pieces. Instead, they require you to build a strategy that fits your health needs, financial situation, and preferences. And the stakes for getting it wrong can be high.
Let’s unpack why a program with just four parts can feel like a maze.
What Each Part Covers and Where It Stops
Medicare Part A: Hospital Insurance
Part A is generally premium-free if you or your spouse paid Medicare taxes for at least 40 quarters. It covers:
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Inpatient hospital stays
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Skilled nursing facility care (limited to 100 days per benefit period)
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Hospice care
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Limited home health services
But it has gaps:
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A hospital deductible per benefit period (in 2025, $1,676)
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Coinsurance after 60 days of hospitalization
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No coverage for long-term custodial care
Medicare Part B: Medical Insurance
Part B covers outpatient care, including:
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Doctor visits
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Preventive screenings
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Outpatient surgeries
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Durable medical equipment
In 2025, the standard monthly premium is $185, and the deductible is $257. After the deductible, you usually pay 20% of the approved amount. Part B does not cover:
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Most dental, vision, and hearing care
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Prescription drugs
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Long-term care
Medicare Part C: Medicare Advantage
Medicare Advantage (Part C) plans are offered by private insurance companies approved by Medicare. These plans must include everything covered by Part A and B, and many include additional benefits like:
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Vision, dental, and hearing coverage
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Gym memberships
But they come with their own rules, costs, and network restrictions. Each plan sets its own:
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Copayments
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Provider networks
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Prior authorization rules
This variation makes it harder to compare plans directly or predict future expenses.
Medicare Part D: Prescription Drug Coverage
Part D covers prescription medications. You enroll in it through a standalone drug plan or as part of a Medicare Advantage plan. In 2025:
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The maximum deductible is $590
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Out-of-pocket drug costs are capped at $2,000
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A new option allows you to spread high drug costs over the year
Yet Part D plans vary widely in:
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Covered medications (formularies)
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Preferred pharmacy networks
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Cost-sharing tiers
Why the Pieces Don’t Always Fit Together
Medicare’s parts are not designed to function as one unified plan. Instead, they require coordination:
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If you have Parts A and B, you need to add Part D separately unless you have other drug coverage.
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You may need a Medigap policy to reduce out-of-pocket costs from Parts A and B.
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Medicare Advantage (Part C) may include drug coverage, but if it doesn’t, you can’t add a standalone Part D.
These decisions can’t be made in isolation. They affect your costs, coverage limits, and provider access.
Timelines That Add to the Confusion
Initial Enrollment Period (IEP)
You can enroll in Medicare during your 7-month Initial Enrollment Period:
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Starts 3 months before your 65th birthday month
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Includes your birthday month
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Ends 3 months after
If you miss this window, you may face lifetime late enrollment penalties for Part B and Part D.
General Enrollment Period (GEP)
If you didn’t sign up during your IEP, you can enroll from January 1 to March 31 each year, with coverage beginning July 1. This delay can leave you uninsured for months.
Medicare Advantage and Part D Open Enrollment
Each year, from October 15 to December 7, you can:
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Switch from Original Medicare to Medicare Advantage
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Switch between Medicare Advantage plans
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Join, switch, or drop a Part D plan
Medicare Advantage Open Enrollment Period (MA OEP)
From January 1 to March 31, those already enrolled in a Medicare Advantage plan can:
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Switch to another Medicare Advantage plan
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Drop it and return to Original Medicare (with or without Part D)
These overlapping timelines can be hard to track, especially when you’re also dealing with retiree coverage, COBRA, or employer benefits.
What’s Missing from Basic Medicare
Even after enrolling in all the core parts, many essential health services still aren’t covered. These include:
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Routine dental exams, cleanings, and dentures
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Eye exams for eyeglasses
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Hearing aids
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Long-term care (e.g., assisted living)
That’s why many people turn to:
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Medigap (Medicare Supplement) policies to cover out-of-pocket costs
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Employer or union retiree coverage if available
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Medicare Advantage for additional benefits
But again, the choice requires trade-offs. Medigap doesn’t work with Medicare Advantage. Some plans require medical underwriting if you join late.
How Medicare Coordinates with Other Coverage
You might have Medicare and:
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Employer coverage (if still working at 65)
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Retiree insurance
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TRICARE or VA benefits
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Medicaid
Each combination has its own coordination rules. For example:
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If your employer has 20+ employees, their coverage usually pays first.
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If fewer than 20, Medicare generally pays first.
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If you delay Part B without other creditable coverage, you could face a penalty.
Failing to understand coordination can result in denied claims or unexpected costs.
Penalties That Stick Around for Life
Medicare penalizes you for not signing up on time unless you qualify for a Special Enrollment Period. These penalties are not one-time fees:
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Part B late enrollment penalty: 10% added to your premium for each 12-month period you delay, applied for life.
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Part D late enrollment penalty: 1% of the national base premium multiplied by the number of uncovered months, also applied for life.
Avoiding these penalties requires timely action and proof of other creditable coverage if you delay enrollment.
Switching Between Plans Isn’t Always Simple
Many assume they can start with a lower-cost plan and switch later if needed. But this isn’t always possible:
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Medigap plans may require medical underwriting if you don’t enroll during your Medigap Open Enrollment Period (6 months after enrolling in Part B at 65).
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Medicare Advantage plans vary each year. Your preferred doctors or medications may not be covered next year.
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You cannot have both a Medigap and a Medicare Advantage plan at the same time.
Decisions made at 65 can impact your options decades later.
The Need for Personalization and Annual Reviews
Medicare isn’t static. Your health needs, finances, and coverage options all change. That’s why:
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You should review your plan annually during Open Enrollment
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Check your ANOC (Annual Notice of Change) for premium or benefit changes
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Ensure your preferred doctors and prescriptions are still covered
What worked last year may no longer fit your needs. Even staying in the same plan without reviewing it can cost you.
Getting the Right Help Matters
The Medicare system is complex by design. Every part has rules, deadlines, exceptions, and fine print. Trying to piece it together alone can lead to costly mistakes or incomplete coverage.
Working with a licensed agent can help you:
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Evaluate your needs based on your health and budget
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Understand enrollment windows and deadlines
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Choose between Original Medicare, Medicare Advantage, and supplements
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Avoid lifetime penalties and coverage delays
Medicare Is a Puzzle, but You Don’t Have to Solve It Alone
Medicare’s four-part structure is only the beginning. What really matters is how those parts are used together, tailored to your situation, and reviewed over time. The challenge lies in putting the puzzle together correctly—and keeping it aligned year after year.
If you’re unsure about where to begin or need help reviewing your current plan, reach out to a licensed agent listed on this website. They can help you understand your options, avoid the common pitfalls, and feel more confident in your Medicare choices.
