Turning 65 is a milestone — and for most people, it comes with a stack of mail about Medicare. If you’ve been putting off sorting through it all, you’re not alone. Medicare has four main parts, and understanding what each one does is the first step toward making confident decisions about your healthcare.
This guide breaks down Medicare Parts A through D in plain language. No jargon, no sales pitch — just the facts you need to get started.
What Is Medicare, Exactly?
Medicare is the federal health insurance program for people 65 and older, certain younger people with disabilities, and people with End-Stage Renal Disease (ESRD). It’s administered by the Centers for Medicare & Medicaid Services (CMS) and is available to eligible individuals across the country.
Most people first encounter Medicare when they turn 65. At that point, you have a seven-month enrollment window — three months before your birthday month, your birthday month, and three months after — called your Initial Enrollment Period (IEP). Missing that window can mean late penalties that stick with you for as long as you have Medicare, so timing matters.
Now let’s look at what each part actually covers.
Part A — Hospital Insurance
Medicare Part A covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home health services. For most people, Part A is premium-free if you or your spouse paid Medicare taxes for at least 10 years (40 quarters). If you haven’t met that threshold, you may pay a monthly premium — but it’s still worth enrolling, since Part A helps cover some of the most expensive types of care.
Think of Part A as your safety net for serious medical events. It won’t cover everything — there are deductibles, coinsurance, and gaps — but it’s the foundation most Medicare beneficiaries build on.
Part B — Medical Insurance
Medicare Part B covers doctor visits, outpatient care, preventive services (like flu shots and cancer screenings), durable medical equipment, and some home health services. Unlike Part A, Part B comes with a standard monthly premium. In 2026, the standard Part B premium is $202.90 per month, though higher-income individuals may pay more through Income-Related Monthly Adjustment Amounts (IRMAA).
Part B also has an annual deductible — $283 in 2026 — after which Medicare generally covers 80% of approved services. That 20% gap is one of the main reasons people explore additional coverage options, which we’ll cover shortly.
Enrolling in Part B on time is critical. If you’re still working and have creditable employer coverage, you may be able to delay enrollment without penalty. But once that employer coverage ends, you have a limited window to sign up. Missing it can result in a late enrollment penalty that increases your monthly premium for as long as you’re enrolled in Part B.
Part C — Medicare Advantage
Medicare Advantage (Part C) is an alternative to Original Medicare (Parts A and B). These plans are offered by private insurance companies approved by Medicare, and they bundle Part A, Part B, and usually Part D (prescription drug coverage) into a single plan. Many Medicare Advantage plans also include extras like dental, vision, hearing, and fitness benefits — coverage that Original Medicare doesn’t provide.
The trade-off is flexibility. Medicare Advantage plans often use provider networks — HMOs, PPOs, or PFFS plans — which means your choice of doctors and hospitals may be more limited than with Original Medicare. Some plans require referrals to see specialists, and out-of-network care can cost more or may not be covered at all.
Medicare Advantage has grown significantly in recent years. Many beneficiaries are attracted to the lower premiums and bundled benefits. But it’s important to understand what you’re giving up in exchange: the ability to see any doctor or specialist who accepts Medicare, without network restrictions.
Part D — Prescription Drug Coverage
Medicare Part D helps cover the cost of prescription medications. Like Part C, Part D plans are offered by private insurers and must meet standards set by CMS. You can get Part D as a standalone plan (if you’re staying with Original Medicare) or as part of a Medicare Advantage plan (MAPD).
Part D plans have their own formularies — lists of covered drugs — and not all plans cover the same medications. If you take prescription drugs regularly, comparing formularies is one of the most important steps in choosing a plan. A plan that looks affordable on premiums might cost you more if your specific medications aren’t on its formulary or are placed in a higher cost-sharing tier.
Each Part D plan also has its own deductible, copayments, and coinsurance structure. And there’s the coverage gap — sometimes called the “donut hole” — which limits how much you pay out of pocket for drugs once your total drug costs reach a certain threshold.
How Do These Parts Work Together?
Most people don’t use just one part of Medicare. Here are the two most common coverage structures:
Original Medicare + Medigap + Part D: You keep Parts A and B, add a Medigap (Medicare Supplement) insurance policy to help cover the gaps in Original Medicare (deductibles, coinsurance, and copayments), and enroll in a standalone Part D plan for prescription drugs. This structure gives you the widest choice of doctors and hospitals — you can see any provider in the country who accepts Medicare — but typically comes with higher monthly premiums.
Medicare Advantage (Part C): You enroll in a Medicare Advantage plan that bundles Parts A, B, and usually D into one plan. Premiums are often lower, and many plans include extra benefits. The trade-off is a more limited provider network and less flexibility.
Neither option is universally “better” — it depends on your health needs, your budget, and the doctors and medications that matter most to you.
What Should You Do Next?
If you’re approaching 65, here are three steps worth taking now:
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Mark your enrollment dates. Your Initial Enrollment Period starts three months before your birthday month. Set reminders so you don’t miss it.
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Review your current coverage. If you’re still working, find out whether your employer plan is considered creditable coverage for Medicare Part B and Part D. If it is, you may be able to delay enrollment without penalty.
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Compare your options. Whether you lean toward Original Medicare with Medigap or a Medicare Advantage plan, comparing plans side by side — premiums, deductibles, networks, and formularies — is the single most valuable thing you can do before enrolling.
Medicare doesn’t have to be overwhelming. When you understand the four parts, the rest falls into place more easily. And you don’t have to figure it out alone — a licensed agent can walk you through your specific situation and help you compare plans without any pressure.
For more information, visit us at trekis.net or call 888-960-0442.
Trek Insurance Solutions is a Third-Party Marketing Organization (TPMO). We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options.