Medigap Plans Explained: What They Are and How They Work with Medicare

If you have Original Medicare (Part A and Part B), you may have noticed that it doesn’t pay 100% of your health care costs. That’s where Medigap plans come in.

This guide walks you through what a Medigap plan is, what it does and does not cover, who can get it, and how it fits into the bigger Medicare picture—so you can better understand whether it might belong in your coverage strategy.

What Is a Medigap Plan?

A Medigap plan (also called Medicare Supplement Insurance) is a type of private insurance policy that helps “fill the gaps” in Original Medicare.

Original Medicare pays a share of covered services, but you are usually responsible for things like:

• Deductibles (what you pay before Medicare starts paying)
• Copayments (fixed dollar amounts you pay for certain services)
• Coinsurance (a percentage of costs you pay after Medicare pays its share)

A Medigap plan is designed to help pay some or all of these out-of-pocket costs for covered services under Original Medicare.

Key idea:
Medigap doesn’t replace Medicare. Instead, it works alongside your existing Medicare Part A and Part B to reduce what you pay when you use covered care.

How Medigap Works with Original Medicare

Here’s the basic flow when you have Original Medicare + a Medigap plan:

1. You go to a doctor or hospital that accepts Medicare.
2. Medicare pays its share of the approved amount.
3. Your Medigap plan helps pay some or all of the remaining amount, depending on which Medigap plan you have.
4. You pay any costs not covered by Medicare or your Medigap policy (such as premiums, and any remaining deductibles or copays if your plan doesn’t cover them fully).

You still:

• Keep your red, white, and blue Medicare card
• Use your Medigap card in addition
• Pay a monthly premium to the Medigap insurer (on top of your Part B premium, and any Part A premium if you have one)

What Medigap Plans Usually Cover

Medigap plans are standardized in most states using lettered options (Plan A, B, C, D, F, G, K, L, M, N). Each lettered plan offers a specific set of benefits, no matter which company sells it.

While details vary by plan, Medigap policies typically help with:

• Medicare Part A coinsurance and hospital costs after Medicare’s initial coverage
• Medicare Part B coinsurance or copayments
• Blood (first 3 pints) for a covered procedure
• Part A hospice care coinsurance or copayments
• Skilled nursing facility care coinsurance (with many, but not all, plan types)
• Part A deductible (in many plans)
• Part B deductible (only in certain older plans, and not available to people newly eligible for Medicare after a certain date)
• Foreign travel emergency care up to plan limits (in some plans)

Not every Medigap plan covers all these items, but these are the core “gaps” they are designed to address.

What Medigap Plans Do NOT Cover

Understanding what Medigap does not cover is just as important:

• Prescription drugs (Part D)
  Modern Medigap plans don’t include drug coverage. Most people who want help with medications enroll in a separate Medicare Part D plan.

• Routine dental, vision, or hearing services
  Things like routine dental cleanings, eyeglasses, or hearing aids are not typically covered by Medigap.

• Long-term care
  Extended stays in a nursing home or assisted living that are primarily custodial care are not covered by Medigap.

• Private-duty nursing, cosmetic procedures, and other services outside Medicare’s covered benefits

Important:
Medigap can only help pay for costs tied to services covered by Original Medicare. If Medicare doesn’t cover a service at all, Medigap generally won’t either.

Medigap vs. Medicare Advantage: How They Differ

This is one of the most common areas of confusion.

Medigap (Medicare Supplement)

• Works with Original Medicare
• Helps pay cost-sharing (deductibles, coinsurance, copays) for covered services
• You can see any provider that accepts Medicare nationwide
• Does not include drug coverage; Part D is separate
• You generally cannot use Medigap with a Medicare Advantage plan

Medicare Advantage (Part C) – For Contrast

• An alternative way to receive Medicare benefits
• Combines Part A and Part B, often with Part D and extra benefits
• Usually uses provider networks (like HMOs or PPOs)
• Has its own copays, rules, and coverage structure
• If you have a Medicare Advantage plan, you cannot also have a Medigap plan for the same coverage

Bottom line:
You usually choose either:

• Original Medicare + Medigap (and often Part D), or
• A Medicare Advantage plan (with or without Part D, depending on the plan)

Common Medigap Plan Types at a Glance

The exact options available depend on your state and when you qualified for Medicare, but here is a simple snapshot of how some popular Medigap plans compare in terms of coverage level for key gaps.

Note: This is a general overview, not a complete benefits list.

*“Coverage level” refers to how many out-of-pocket gaps the plan helps with, not the quality of care.

Different plans balance monthly premiums versus how much they pay when you use care. Higher-coverage plans tend to have higher premiums but lower bills when you receive services, and vice versa.

Who Is Eligible for a Medigap Plan?

To buy a Medigap policy, you generally must:

• Be enrolled in Medicare Part A and Part B
• Live in a state where the insurer sells the plan you want
• Not be enrolled in a Medicare Advantage plan at the same time (or be willing to switch back to Original Medicare to use Medigap)

Some states have additional protections or unique rules, especially for people under 65 who qualify for Medicare due to disability. In many places, access and pricing for under-65 enrollees can be more limited or handled differently.

When Can You Enroll in a Medigap Plan?

The most important window is your Medigap Open Enrollment Period.

Your Medigap Open Enrollment Period

This is a six-month window that:

• Starts the first month you are both:
  • 65 or older, and
  • Enrolled in Medicare Part B
• Lasts for six months from that date

During this time:

• You generally have the right to buy any Medigap plan offered in your state (that you’re eligible for)
• Medical underwriting (health questions, potential denials, or higher premiums based on health) often cannot be used against you

This period is a one-time opportunity for many people, so the timing can be very important.

After Your Medigap Open Enrollment Period

If you apply for Medigap after your open enrollment window, insurers in many states may:

• Use medical underwriting
• Potentially charge more based on your health
• In some cases, deny coverage

There are certain “guaranteed issue” rights in specific situations—such as losing other coverage or your plan leaving Medicare—where you may still have protections to buy a Medigap policy without medical underwriting. The exact details depend on your circumstances and state rules.

How Much Do Medigap Plans Cost?

With Medigap, you usually pay:

1. Your monthly Medicare Part B premium
2. Your monthly Medigap premium
3. Any remaining deductibles, copays, or coinsurance that your plan does not cover
4. A separate Part D premium if you choose a drug plan

Medigap premiums vary widely based on factors such as:

• Which plan letter you choose (e.g., Plan G vs. Plan N)
• Your age
• Where you live
• Whether the policy uses an age-based pricing method
• Whether you are eligible for any discounts (for example, some carriers may offer discounts for non-smokers or for paying electronically)

Medigap plans with broader coverage usually have higher premiums but can lead to more predictable costs when you use services. Plans with less coverage may cost less each month but may result in higher bills when you receive care.

How to Compare Medigap Plans

When you compare Medigap options, it can help to look at both benefits and costs together.

Here are some practical points to consider:

1. Benefits vs. Monthly Premium

Ask yourself:

• How much risk are you comfortable taking on in medical bills?
• Would you rather pay more each month for more comprehensive coverage or less each month and accept higher potential out-of-pocket costs?

2. Your Typical Health Care Use

Think about:

• How often you see doctors or specialists
• Whether you travel frequently within or outside the U.S.
• If you anticipate frequent outpatient services, physical therapy, or other ongoing care

Different Medigap plans can be more or less appealing depending on your usual pattern of care.

3. Provider Flexibility

One of the core advantages people often value with Medigap is:

• The ability to go to any doctor or hospital that accepts Medicare, without network restrictions

If seeing specific specialists or having flexibility when traveling is important, this aspect may carry extra weight.

4. Long-Term Budget Planning

Because Medigap is a monthly commitment, some people look at:

• How premiums might change over time
• How predictable they want their health care costs to be from year to year

Some plans may have lower premiums at first but increase faster over time, while others may be priced differently depending on how they’re structured.

Key Rules and Limitations to Keep in Mind

To avoid surprises, it helps to remember these structural rules about Medigap:

• You cannot use Medigap with a Medicare Advantage plan.
  If you enroll in Medicare Advantage, you typically cannot keep or use your Medigap plan for that coverage.

• One Medigap policy per person.
  Medigap only covers one person. Couples need separate Medigap policies if both want coverage.

• Standardized benefits by letter.
  In most states, a Medigap Plan G from one company must cover the same core benefits as a Plan G from another company. The main differences are usually the premium, customer service, and optional features, not the basic covered gaps.

• Medigap is not a drug plan.
  If you need medication coverage, you usually need a separate Part D plan.

• Policies are guaranteed renewable.
  As long as you pay your premiums on time and the company remains in the market, your policy generally cannot be canceled due to your health or claims history.

When a Medigap Plan May Be Worth Considering

People often explore Medigap when they:

• Want to stay with Original Medicare but reduce their share of deductibles, coinsurance, and copays
• Prefer the freedom to choose any Medicare-accepting provider without networks
• Travel frequently within the U.S., or internationally (if considering a plan that includes foreign travel emergency coverage)
• Value predictable, stable cost-sharing rather than varying copays for each type of service

A Medigap plan is not the right fit for everyone, but it is one of the main ways to enhance Original Medicare and manage out-of-pocket expenses more closely.

Simple Summary: What Is a Medigap Plan?

To bring it all together:

• Medigap = Medicare Supplement Insurance.
• It is optional private coverage that works with Original Medicare.
• Its main purpose is to help pay Medicare’s out-of-pocket costs like deductibles, copays, and coinsurance.
• Medigap does not cover everything—no routine dental/vision/hearing, no long-term care, and no current prescription drug coverage.
• You can’t pair Medigap with Medicare Advantage; you typically choose one path or the other.
• The best time to enroll is usually during your six-month Medigap Open Enrollment Period when you first have Part B and are 65 or older.
• Plans are standardized by letter, but premiums and company-specific features can differ.

Understanding how Medigap plans work gives you a clearer picture of how to fill the gaps in Original Medicare and structure your coverage in a way that aligns with your budget, health needs, and preferences for flexibility.