What Are Medicare Plans? Parts A, B, C & D Plus Medigap

Medicare covers over 67 million Americans as of 2026, yet many people approaching eligibility still ask the same fundamental question: what are Medicare plans, and how do the different parts actually work? That confusion is understandable. Between Parts A, B, C, and D, plus Medigap policies, the program has a lot of moving pieces, and each one covers something different.

Getting the basics right matters. Choosing the wrong plan (or missing a key enrollment window) can leave you with coverage gaps and unexpected out-of-pocket costs that follow you for years. The good news is that once you understand how each part functions, the decisions become far more straightforward.

At Golden Health and Life Agency, we help seniors and Medicare-eligible individuals sort through options from over 300 carriers to find coverage that fits both their health needs and their budget. This guide breaks down every part of Medicare, explains how Original Medicare differs from Medicare Advantage, and covers where supplemental plans fit in, so you can make an informed choice with confidence.

What Medicare plans are and who qualifies

When people ask what are Medicare plans, the short answer is this: Medicare is a federal health insurance program administered by the Centers for Medicare and Medicaid Services (CMS). Created in 1965, it gives older Americans and certain disabled individuals access to health coverage they might not otherwise afford. The program does not work like a single plan you sign up for once. Instead, it consists of multiple parts, each covering a specific category of healthcare costs, and you build your coverage by combining those parts based on your situation.

Medicare is not one-size-fits-all. The parts you need depend entirely on your health situation, your prescriptions, and how you prefer to receive care.

Who is eligible for Medicare

Most people qualify for Medicare at age 65, provided they or their spouse paid Medicare taxes for at least 10 years (40 quarters) while working. You may also become eligible before age 65 under specific circumstances:

• You have received Social Security Disability Insurance (SSDI) for 24 consecutive months

• You have End-Stage Renal Disease (ESRD) requiring dialysis or a transplant

• You have been diagnosed with Amyotrophic Lateral Sclerosis (ALS)

U.S. citizenship or permanent legal residency is also required in all cases.

What counts as a Medicare plan

The term "Medicare plan" covers several distinct options under the same program umbrella. Original Medicare includes Part A and Part B, which the federal government manages directly. Beyond that, private insurers approved by Medicare offer Medicare Advantage (Part C) and Part D prescription drug plans as alternatives or add-ons.

Medigap policies, sold by private companies, layer on top of Original Medicare to help cover costs like copayments and deductibles. Each option carries its own premiums, coverage rules, and provider networks, so the combination that fits one person may leave another exposed to significant out-of-pocket costs. Knowing how these pieces connect is the foundation of every smart Medicare decision.

Medicare Part A and Part B basics

Original Medicare consists of two distinct parts: Part A and Part B. Before exploring what are Medicare plans in their more advanced forms, you need to understand these two parts, since every other coverage option either replaces or builds on top of them.

What Part A covers

Part A is your hospital insurance. It covers inpatient hospital stays, skilled nursing facility care following a qualifying hospital stay, hospice care, and some home health services. Most people pay no premium for Part A because they or their spouse paid Medicare taxes during their working years. In 2026, the inpatient hospital deductible sits at $1,676 per benefit period.

If you need skilled nursing facility care after a hospital stay, Part A covers the first 20 days in full, but days 21 through 100 carry a daily coinsurance charge.

What Part B covers

Part B handles your outpatient medical care. This includes doctor visits, preventive screenings, lab tests, durable medical equipment, and outpatient procedures. Unlike Part A, most beneficiaries pay a monthly premium for Part B, which is $185.00 in 2026 for most enrollees. You also face a $257 annual deductible, followed by 20% coinsurance for most covered services after that threshold is met.

Medicare Part C and Part D basics

Once you understand Original Medicare, the next layer of what are Medicare plans involves private insurance options. Part C and Part D are both run by private companies that Medicare has approved, and each one covers a distinct set of needs within the broader program.

What Part C (Medicare Advantage) covers

Medicare Advantage combines your Part A and Part B benefits into a single private plan, often adding extras like dental, vision, and hearing coverage that Original Medicare does not include. You still pay your Part B premium, but many plans charge low or $0 additional monthly premiums in exchange for using a defined provider network such as an HMO or PPO.

Medicare Advantage plans must cover everything Original Medicare covers, but cost-sharing structures and provider networks differ significantly from plan to plan.

Your location plays a major role here. Plan availability and pricing vary by county, so two people in different zip codes may have access to very different options.

What Part D covers

Part D provides prescription drug coverage, either as a standalone plan added to Original Medicare or as a benefit bundled into a Medicare Advantage plan. Each plan maintains a formulary, which is its approved drug list, organized into tiers that determine your copays.

Formularies change every year, so reviewing your plan each fall during Open Enrollment prevents unexpected cost increases on medications you rely on.

Medigap and other ways to add coverage

One part of understanding what are medicare plans involves knowing how to fill the gaps Original Medicare leaves behind. Part A and Part B together still leave you responsible for deductibles, copayments, and 20% coinsurance on outpatient services. Medigap policies exist specifically to cover those leftover costs.

How Medigap works

Medigap is supplemental insurance sold by private companies to work alongside Original Medicare, not Medicare Advantage. These standardized plans, labeled Plan G, Plan N, and others, cover some or all of your cost-sharing obligations depending on the plan you choose. You pay a separate monthly premium for Medigap coverage on top of your Part B premium.

The best time to buy a Medigap policy is during your 6-month Medigap Open Enrollment Period, which starts the month you turn 65 and enroll in Part B, because insurers cannot deny coverage or charge higher premiums based on your health during this window.

Other coverage add-ons to consider

Dental, vision, and hearing coverage are not included in Original Medicare, which surprises many new enrollees. Some standalone supplemental plans address these specific gaps. Medicare Savings Programs can also help low-income beneficiaries cover premiums and cost-sharing, so checking your eligibility through your state Medicaid office is worth your time.

How to choose and enroll without penalties

Knowing what are Medicare plans is only useful if you also know when and how to sign up. Missing key enrollment windows triggers permanent late enrollment penalties that raise your premiums for life, so timing matters as much as plan selection.

When your enrollment windows open

Your Initial Enrollment Period (IEP) spans seven months: three months before the month you turn 65, your birthday month, and three months after. If you miss this window, you must wait for the General Enrollment Period, which runs January 1 through March 31 each year, with coverage starting July 1.

Enrolling late in Part B carries a 10% premium penalty for each full 12-month period you went without coverage, and that penalty never goes away.

How to pick the right plan

Comparing plans on cost alone is a common mistake. You should also weigh your current medications against each plan's formulary, check whether your preferred doctors are in-network, and factor in any specialist care you use regularly. Medicare's Plan Finder tool at medicare.gov lets you compare options side by side based on your specific prescriptions and location. Key factors to review before enrolling include:

• Monthly premium and annual deductible

• Drug formulary coverage for your current prescriptions

• Provider network and specialist access

Key Takeaways and Next Steps

Understanding what are Medicare plans comes down to knowing how the parts work together. Part A covers hospital care, Part B handles outpatient services, and together they form Original Medicare. Part C bundles those benefits through a private insurer and often adds extras, while Part D covers your prescriptions separately. Medigap fills the cost gaps that Original Medicare leaves behind.

Your next step is to match those options against your actual situation. Your doctors, your current medications, and your expected healthcare use should drive your decision, not just the monthly premium. Missing enrollment windows or picking a plan without reviewing the drug formulary can cost you significantly more over time, so plan selection deserves careful attention.

Getting the right plan is easier with expert guidance. If you want help comparing options from over 300 carriers, speak with a Medicare specialist at Golden Health and Life Agency to find coverage that fits your health needs and budget.