Medicare A, B, C & D Explained: Complete Parts Guide

Understanding Medicare can feel overwhelming when you’re first turning 65. With Parts A, B, C, and D, plus supplement plans and Medicare Advantage options, it’s no wonder thousands of people call me every year asking the same question: “Alex, what does all of this actually mean?” Let me break it down in simple terms so you can make an informed decision about your Medicare coverage.

The Four Parts of Medicare Explained

Medicare is divided into four distinct parts, each covering different aspects of your healthcare needs. Understanding what each part covers is crucial for making the right decisions about your coverage.

Medicare Part A (Hospital Insurance)

Part A covers facility-based care, which includes hospitals, skilled nursing facilities, mental health facilities, and hospice care. The good news is that Part A is generally premium-free if you’ve worked and paid into Medicare for at least 10 years (40 quarters). However, there’s still a deductible of $1,736 for each benefit period when you’re admitted to a hospital.

Medicare Part B (Medical Insurance)

Part B is your medical insurance that covers doctor visits, outpatient facilities, durable medical equipment, lab services, blood work, MRIs, and x-rays. Unlike Part A, Part B comes with a monthly premium of $202.90 in 2026, though this amount can increase significantly if your income exceeds certain thresholds. Part B also has an annual deductible of $283.

Medicare Part C (Medicare Advantage)

Part C refers to Medicare Advantage plans, which are optional alternatives to Original Medicare. These plans are offered by private insurance companies and essentially replace your Medicare Parts A and B coverage.

Medicare Part D (Prescription Drug Coverage)

Part D provides prescription drug coverage and is also optional. However, if you don’t enroll when you’re first eligible and don’t have other creditable drug coverage, you’ll face a permanent late enrollment penalty.

Parts A and B together make up what we call “Original Medicare,” which is the foundation of your Medicare coverage.

Agent Tip

Many of my clients assume Medicare Part A is completely free, but you still face that $1,736 deductible each time you’re hospitalized. This catches a lot of people off guard on their first hospital bill.

Your Two Main Medicare Coverage Paths

Once you understand the four parts of Medicare, you need to choose between two primary coverage approaches. This decision will significantly impact your healthcare costs and access to providers.

Option 1: Original Medicare + Medicare Supplement + Part D Drug Plan

This path involves keeping your Original Medicare (Parts A and B) and adding a Medicare Supplement plan (also called Medigap) plus a separate Part D prescription drug plan.

Medicare Supplement Plans

Medicare Supplement plans offer several significant advantages. There are no networks to worry about—you can see any doctor nationwide that accepts Medicare. You don’t need referrals to see specialists, and most plans include international emergency coverage. However, you’ll need to purchase a separate Part D drug plan since supplements don’t include prescription coverage.

The most popular supplement options are Plan G and Plan N.

Plan G Coverage

Plan G is the most comprehensive Medicare Supplement option available to new Medicare beneficiaries. After you pay the annual $283 deductible for doctor visits and outpatient services, Plan G covers virtually everything else that Medicare approves. You won’t face any copays for covered services, making it the most predictable option for budgeting your healthcare costs.

Plan N Coverage

Plan N offers slightly less coverage but comes with lower monthly premiums. You’ll pay a $20 copay for office visits and a $50 copay for emergency room visits (waived if you’re admitted to the hospital). Like Plan G, Plan N has the $283 annual deductible. The main difference is that Plan N doesn’t cover Part B excess charges, though these are rare and only occur in states that allow them when providers don’t accept Medicare assignment.

High Deductible Plan G

There’s also a high deductible version of Plan G with a $2,950 deductible for 2026. This option works well for healthy individuals who want comprehensive coverage but prefer lower monthly premiums in exchange for higher out-of-pocket costs if they need care.

Medicare Supplement plans typically cost $100 or more per month, with higher premiums in states like New York, California, and Florida due to state regulations and demographics.

Option 2: Medicare Advantage

Medicare Advantage plans are administered by private insurance companies like Humana and United Healthcare. These plans completely replace your Original Medicare coverage, combining Parts A, B, and usually D into a single plan.

Most Medicare Advantage plans have $0 monthly premiums beyond your required Part B premium. However, they operate with network restrictions, coming as either HMO or PPO plans. You’ll typically need to stay within the plan’s network of providers and may need referrals to see specialists.

Medicare Advantage plans usually include additional benefits like dental, vision, and hearing coverage that Original Medicare doesn’t provide. However, they come with out-of-pocket maximums that can range from a few thousand dollars up to $7,000 annually.

Agent Tip

For my Medicare Advantage clients, I always recommend adding a secondary hospital indemnity plan with a cancer rider. This provides additional protection since Advantage plans can leave you with significant out-of-pocket costs during major medical events.

Key Differences Between Your Options

Feature	Medicare Supplement	Medicare Advantage
Monthly Premium	$100+ (plus Part D)	Usually $0
Provider Networks	No networks	Network required
Referrals	Not required	Often required
Out-of-Pocket Maximum	Very low with Plan G	$2,000-$7,000
Extra Benefits	Limited	Dental, vision, hearing

The fundamental difference comes down to this: Medicare Supplement plans offer maximum coverage with predictable, low out-of-pocket costs but higher monthly premiums. Medicare Advantage plans offer low or no premiums but potentially higher out-of-pocket costs when you need care.

My Professional Recommendation

After working with thousands of Medicare beneficiaries, I typically recommend starting with a Medicare Supplement plan if you can afford the monthly premium. Here’s why: during your Initial Enrollment Period when you first become eligible for Medicare, you can enroll in any supplement plan without health questions or medical underwriting.

This guaranteed issue period is incredibly valuable. If you choose Medicare Advantage initially and later want to switch to a supplement plan, you may face health underwriting, which could result in higher premiums or even denial of coverage based on your health conditions.

The beauty of supplement plans is that you can always move from a supplement to Medicare Advantage later without any health questions. However, going the other direction—from Advantage to supplement—often requires medical underwriting after your first year.

If budget constraints make supplement plans unaffordable, Medicare Advantage can be a reasonable alternative. Just understand that you’re trading lower monthly costs for potentially higher costs when you actually need medical care.

Making Your Decision

When choosing between these options, consider your current health status, budget, and preference for provider flexibility. If you want the freedom to see any Medicare-accepting doctor without referrals and prefer predictable costs, a Medicare Supplement plan is likely your best choice. If you’re healthy, budget-conscious, and comfortable with network restrictions, Medicare Advantage might work well for you.

Remember, timing is crucial with Medicare. Missing your Initial Enrollment Period can result in permanent penalties and limited options for supplement coverage.

Frequently Asked Questions

What’s the difference between Medicare Part C and Medicare Advantage?

There’s no difference—Medicare Part C is just the official name for Medicare Advantage plans. Both terms refer to the same private insurance plans that replace Original Medicare.

Do I need both a Medicare Supplement and Medicare Advantage?

No, you cannot have both. You must choose either Original Medicare with a supplement plan or Medicare Advantage. Having both is not allowed and would be redundant coverage.

Can I switch from Medicare Advantage to a Medicare Supplement later?

Yes, but after your first year, you’ll likely need to answer health questions and may face medical underwriting. This could result in higher premiums or coverage denial if you have health issues.

Is Medicare Part D required?

Part D isn’t technically required, but if you don’t enroll when first eligible and lack other creditable drug coverage, you’ll face a permanent late enrollment penalty when you do eventually sign up.

Which Medicare path costs less overall?

It depends on your health and usage. Medicare Supplement plans have higher monthly premiums but lower costs when you need care. Medicare Advantage has lower monthly costs but potentially higher out-of-pocket expenses during illness or injury.