Medicare can cover a lot of your healthcare expenses—but it doesn't necessarily cover everything.

That can leave people asking an important question:

“What happens to the costs Medicare doesn't pay?”

That's where Medicare Supplement Insurance, commonly called Medigap, comes in.

Medigap is private insurance designed to help pay certain out-of-pocket costs that come with Original Medicare, such as coinsurance, copayments, and deductibles.

But there's one important thing to understand right away:

Medigap is not the same thing as Medicare Advantage.

They work in very different ways.

If you're approaching Medicare—or already enrolled—understanding that difference can make the choices in front of you feel much less confusing.

Let's make it simple.

What Is Medicare Supplement Insurance?

Medicare Supplement Insurance is additional insurance you can purchase from a private insurance company to help pay some of the healthcare costs that Original Medicare doesn't fully cover.

Original Medicare consists of:

• Medicare Part A — hospital insurance

• Medicare Part B — medical insurance

With Original Medicare, Medicare pays its share of covered healthcare costs, and you are responsible for your share. A Medigap policy can help with some of those remaining costs. For example, Medicare.gov explains that Medigap policies can help cover costs such as:

• Coinsurance

• Copayments

• Deductibles

Some Medigap policies can also provide limited coverage for emergency care when traveling outside the United States.

Think of it this way:

Original Medicare = your primary Medicare coverage

Medigap = additional coverage that can help with certain costs left behind

Why Do People Consider Medigap?

One of the biggest reasons people look at Medicare Supplement Insurance is predictability.

Healthcare expenses can be difficult to budget for when you don't know how much you might owe after Medicare pays its portion.

A Medigap policy can help reduce some of those out-of-pocket costs, depending on the plan you choose. For someone who wants Original Medicare's provider flexibility but also wants additional help with certain cost-sharing expenses, Medigap may be something worth learning about.

However, every person's situation is different. The goal isn't simply to choose a policy because someone else has it. The goal is to understand how the coverage works and whether it fits your healthcare and financial needs.

How Does Medigap Work?

Here's a simplified example. Imagine you have:

Original Medicare + a Medigap policy

You receive a Medicare-covered medical service. Generally, Medicare processes the claim first and pays its share of the Medicare-approved amount. Then, depending on your Medigap policy, the Medigap insurer may help pay some of the remaining amount.

You are responsible for anything your Medicare and Medigap coverage don't pay. That's the basic idea.

Medigap doesn't replace Medicare. It works alongside Original Medicare.

What Does Medigap Cover?

The exact benefits depend on the Medigap plan.

Medigap policies are standardized in most states. Plans are identified by letters, such as:

• Plan A

• Plan B

• Plan G

• Plan K

• Plan L

• Plan M

• Plan N

The benefits associated with a particular lettered plan are standardized in most states, meaning the same plan letter generally provides the same standardized benefits regardless of which insurance company sells it.

That can make comparing policies easier. For example, if you're comparing the same standardized Medigap plan from two different companies, the primary difference can be the price and company, rather than completely different medical benefits.

But premiums can vary based on factors such as where you live and the policy you choose.

What Doesn't Medigap Cover?

This is just as important as understanding what it does cover. Medigap generally does not cover everything.

Medicare.gov says Medigap generally doesn't cover:

• Long-term care, such as nursing home care

• Routine vision care

• Dental care

• Hearing aids

• Eyeglasses

• Private-duty nursing

• Prescription drugs

Prescription drug coverage is especially important to understand. Medigap policies sold after 2005 don't include prescription drug coverage. If you want Medicare prescription drug coverage, you can generally enroll in a separate Part D plan when using Original Medicare.

So don't assume that having Medigap means you have every type of Medicare-related coverage you need.

Medigap vs. Medicare Advantage: What's the Difference?

This is where Medicare can get confusing. Medigap and Medicare Advantage are not two versions of the same thing. They are fundamentally different approaches to Medicare coverage.

Medicare Supplement / Medigap

Medigap works with Original Medicare.

You generally:

• Have Medicare Part A and Part B

• Keep Original Medicare

• Purchase a Medigap policy from a private insurer

• May purchase a separate Part D prescription drug plan

• Use doctors and hospitals that accept Medicare

Medicare Advantage

Medicare Advantage, also called Part C, is another way to receive your Medicare coverage through a Medicare-approved private health plan.

Medicare Advantage plans must cover Medicare-covered medically necessary services, but they may also offer additional benefits. Many plans include prescription drug coverage.

There can also be differences in provider networks, prior authorization requirements, premiums, copayments, and other costs.

Here's a simple way to remember it:

Medigap works with Original Medicare. Medicare Advantage replaces the way you receive your Medicare Part A and Part B benefits.

You generally can't have Medigap and Medicare Advantage at the same time. Medicare.gov states that Medigap is only available when you have Original Medicare.

What About Doctors?

For many people, doctor access is an important part of the decision. With Original Medicare, you can generally see any doctor or hospital that accepts Medicare, anywhere in the United States.

Medicare Advantage plans, on the other hand, may use provider networks and service areas, and some plans may require prior authorization for certain services. That doesn't automatically make one option right or wrong.

It simply means the structure is different. If you have doctors you already trust, checking how they participate in the coverage you're considering can be an important part of your research.

When Can You Buy Medigap?

Timing matters. Medicare provides a 6-month Medigap Open Enrollment Period that starts when you're 65 or older and have Part B. During this period, you generally have important protections: you can buy any Medigap policy sold in your state, even if you have health problems.

This period is different from Medicare's annual Open Enrollment Period.

That's an easy distinction to miss.

Medigap Open Enrollment

One-time 6-month period connected to getting Part B at age 65 or older.

Medicare Open Enrollment

Annual period when people can make certain changes to their Medicare coverage. Your Medigap Open Enrollment Period doesn't simply come back every year. Medicare.gov notes that it is a one-time enrollment period.

After that period ends, you may have fewer options or potentially pay more depending on your circumstances and state rules. Certain situations can provide guaranteed-issue rights or other opportunities to buy Medigap, so timing and individual circumstances matter.

How Much Does Medigap Cost?

There isn't one universal Medigap price.

Your premium can depend on:

• The plan you choose

• Where you live

• The insurance company

• Your circumstances and rating method

• Other factors used by the insurer

Medicare.gov notes that Medigap premiums vary depending on the policy, location, and other factors, and premiums can change over time. And remember: A Medigap premium is in addition to your Medicare Part B premium.

That means you shouldn't look at the Medigap premium by itself.

Instead, consider the bigger picture: What will your total monthly and potential out-of-pocket healthcare costs look like?

What Are Medigap Plan Letters?

If you've started researching Medicare Supplement Insurance, you've probably seen names like Plan G or Plan N. It can sound like a secret code at first. It's really just a way of identifying standardized benefit structures.

Different Medigap plans cover different portions of Medicare cost-sharing.

For example, the 2026 Medicare materials show differences among Plans A, B, D, G, K, L, M and N in areas such as Part A coinsurance, Part B coinsurance, deductibles, skilled nursing facility coinsurance and foreign-travel emergency coverage.

The important part is:

Don't choose a plan based only on the letter. Look at what the plan actually covers, what it costs, and how those benefits fit your situation.

Is Medigap Right for Everyone?

Not necessarily. Some people prefer Original Medicare with supplemental coverage. Others may prefer Medicare Advantage.

There are also people who have other coverage, such as employer or retiree coverage, Medicaid, or other forms of assistance. Medicare itself points out that people have different coverage options and circumstances.

The right questions to ask aren't simply:

“Which plan is best?”

Instead, consider:

• Do I want Original Medicare?

• How important is provider flexibility to me?

• Do my doctors accept Medicare?

• What prescription coverage do I need?

• How much am I comfortable paying in premiums?

• How much do I want to budget for healthcare expenses?

• Do I travel outside the United States?

• Am I within my Medigap Open Enrollment Period?

• Do I have other health coverage?

Those questions can give you a much clearer starting point.

A Simple Medigap Checklist

If you're considering Medicare Supplement Insurance, start here:

1. Understand Original Medicare

Know what Parts A and B cover and what costs you may still be responsible for.

2. Look at your healthcare needs

Think about your doctors, medications, specialists and expected healthcare use.

3. Check your enrollment timing

Your Medigap Open Enrollment Period can be particularly important because of the protections available during that period.

4. Compare standardized plans

Understand what each plan letter covers before comparing prices.

5. Compare insurance companies

If you're looking at the same standardized plan, compare premiums and other company-specific considerations.

6. Look at the whole picture

Don't focus only on the monthly premium. Think about your potential out-of-pocket costs, prescription coverage and overall healthcare budget.

Medicare Doesn't Have to Feel Like a Different Language

At first glance, Medicare can feel like you're learning an entirely new vocabulary.

• Part A.

• Part B.

• Part D.

• Medigap.

• Medicare Advantage.

• Plan G.

• Plan N.

And then there are enrollment periods, premiums, deductibles and networks. It's a lot. That's why education matters. At We Know Life & Health, Dale Earp and Rachel Earp believe people shouldn't have to feel overwhelmed just because healthcare insurance has complicated terminology.

The goal isn't to make the decision for you. It's to help you understand your options so you can ask better questions and make a decision that fits your circumstances.

Frequently Asked Questions About Medicare Supplement Insurance

Is Medicare Supplement Insurance the same as Medicare Advantage?

No. Medigap works alongside Original Medicare and helps pay certain out-of-pocket costs. Medicare Advantage is an alternative way to receive Medicare Part A and Part B benefits through a Medicare-approved private plan.

Can I have Medigap and Medicare Advantage?

Generally, no. Medigap is designed to work with Original Medicare, not Medicare Advantage.

Does Medigap cover prescription drugs?

Generally, no. Medigap policies sold after 2005 don't include prescription drug coverage. People with Original Medicare can generally get prescription coverage through a separate Part D plan.

Does Medigap cover dental and vision?

Generally, Medigap doesn't cover routine dental or vision care.

Do all Medigap plans have the same benefits?

Standardized Medigap plans with the same letter generally have the same standardized benefits in most states, although premiums and the companies offering them can differ.

When is the best time to enroll in Medigap?

Your 6-month Medigap Open Enrollment Period, which generally begins when you're 65 or older and have Part B, provides important protections. During that period, you can generally buy any Medigap policy sold in your state even if you have health problems.

The Bottom Line

Medicare Supplement Insurance can sound complicated, but the basic idea is fairly simple: Medigap helps fill certain cost gaps left by Original Medicare.

It can help with expenses such as coinsurance, copayments and deductibles, depending on the plan you choose. But Medigap isn't Medicare Advantage, it doesn't cover everything, and timing can matter when you're applying.

If you're approaching Medicare or reviewing your current coverage, take the time to understand how your coverage works—not just what it's called. And if you're unsure where to start, that's exactly what education is for. We Know Life & Health is here to help make insurance make sense.

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Education first. Relationships always.