Medigap Plans Can Be a Safety Net—But They Only Work If You Get the Timing Right

Key Takeaways

• Medigap plans offer critical protection against out-of-pocket Medicare costs, but the timing of your enrollment determines whether you’re guaranteed approval or subject to medical underwriting.

• Missing your Medigap Open Enrollment Period can result in higher premiums or denial of coverage, especially if you have pre-existing conditions.

What Is a Medigap Plan and Why It Matters in 2025

Medigap plans, also known as Medicare Supplement Insurance, are designed to help cover the “gaps” in Original Medicare. These gaps include deductibles, coinsurance, and copayments that you’re responsible for under Parts A and B.

In 2025, Medigap plans continue to play a vital role in providing financial predictability and reducing out-of-pocket exposure. While Medicare covers a wide range of services, it does not cover everything. That’s where Medigap comes in—to offer peace of mind and stable budgeting for healthcare needs.

Understanding the Medigap Open Enrollment Period

The most important timing window for Medigap is your Medigap Open Enrollment Period (OEP). This is a one-time six-month window that begins the first month you’re both 65 or older and enrolled in Medicare Part B.

During this period:

• You have a guaranteed issue right to buy any Medigap plan sold in your state.

• Insurance companies cannot deny you coverage based on pre-existing conditions.

• You will not be subject to medical underwriting.

If you miss this window, your application may be denied, or you may pay significantly higher premiums due to your health history.

Special Cases

If you’re under 65 and eligible for Medicare due to disability, your state might offer additional enrollment protections. However, these vary widely, and not all insurers must sell you a Medigap plan until you turn 65.

After the Open Enrollment Period: What Changes?

Once your six-month Medigap Open Enrollment Period ends, insurers can require medical underwriting unless you qualify for a guaranteed issue right through a special circumstance.

In these cases, the insurer can:

• Deny your application

• Charge higher premiums

• Impose waiting periods for pre-existing conditions (up to six months)

Guaranteed issue rights may apply if:

• You lose other coverage through no fault of your own

• Your Medicare Advantage Plan stops operating in your area

• You leave a Medicare Advantage Plan within the first 12 months and want to return to Original Medicare

These rights are time-sensitive, usually lasting 60 days from the date your other coverage ends.

Medigap Doesn’t Work With Medicare Advantage

It’s crucial to understand that Medigap plans do not work with Medicare Advantage (Part C). If you have Medicare Advantage, you cannot use a Medigap plan to cover your out-of-pocket costs.

You must:

• Be enrolled in Original Medicare (Parts A and B) to be eligible for Medigap

• Drop your Medicare Advantage Plan before your Medigap coverage begins

Because switching from Medicare Advantage to Original Medicare may only be possible during specific periods, you must plan this transition carefully to avoid gaps in coverage.

Why Timing Is Financially Critical

Delaying Medigap enrollment beyond your Open Enrollment Period doesn’t just risk denial—it can lead to significantly higher costs over time.

Let’s say you wait two years after becoming eligible:

• You may face age-based premium increases

• Medical underwriting may increase costs or limit choices

• You could end up with a plan that doesn’t meet your needs

Getting in at the right time means locking in a plan while you’re in the best position to control your options and expenses.

What Medigap Covers and What It Doesn’t

Medigap plans are standardized in most states, meaning Plan A in one state will offer the same basic benefits as Plan A in another.

Medigap typically covers:

• Medicare Part A coinsurance and hospital costs

• Medicare Part B coinsurance or copayments

• Blood (first three pints)

• Part A hospice care coinsurance or copayment

• Skilled nursing facility care coinsurance (in some plans)

• Part A and Part B deductibles (depending on the plan)

• Foreign travel emergency care (in some plans)

Medigap does not cover:

• Prescription drugs (you need a separate Part D plan)

• Routine dental, vision, or hearing care

• Long-term care

• Private-duty nursing

You should also know that Medigap plans sold after January 1, 2020, cannot cover the Part B deductible, due to federal regulation changes.

Choosing a Plan: Standardization Helps, But Comparison Still Matters

In most states, Medigap plans are labeled A through N. Each lettered plan offers a different set of standardized benefits.

That means:

• A Plan G in one state has the same core benefits as a Plan G in another

• The difference lies in monthly premiums and service from the insurer

It’s essential to compare:

• Coverage details

• Premiums by age and zip code

• Rate increase history

• Customer service ratings

Some states like Massachusetts, Minnesota, and Wisconsin have different standardization models, so if you live in one of those states, the naming and benefits may vary.

Important Enrollment Periods to Be Aware Of

Here are key timelines in 2025 to keep in mind:

• Initial Enrollment Period: Starts three months before the month you turn 65, includes your birthday month, and ends three months after.

• Medigap Open Enrollment Period: Begins the first month you’re 65 or older and enrolled in Medicare Part B.

• Medicare Advantage Open Enrollment: January 1 to March 31. If you leave a Medicare Advantage plan, you can return to Original Medicare and apply for a Medigap plan, although underwriting may apply.

• Annual Open Enrollment (for Part D or Medicare Advantage): October 15 to December 7. This is not a Medigap enrollment window.

Common Misconceptions About Medigap Timing

• You can enroll anytime: Technically true, but after your OEP, you’re not guaranteed acceptance.

• You don’t need Medigap if you’re healthy: Healthcare needs change with age. If you delay and develop a condition, it may be too late to get full coverage.

• Medigap covers everything Medicare doesn’t: It helps with many out-of-pocket costs but doesn’t cover services like dental, vision, or prescriptions.

• You can switch plans freely: Switching after OEP often requires underwriting, and your options may be limited based on your health.

Steps to Take If You Missed Your Medigap Open Enrollment

If you’re outside your Open Enrollment Period and want to apply for a Medigap plan:

• Check for any guaranteed issue rights you may have based on your current situation.

• Call insurers directly to see if they’ll accept your application without underwriting.

• Be ready for medical underwriting—prepare your health records and medications list.

• Shop around—some companies are more flexible than others.

Final Thoughts on Timing Your Medigap Enrollment Right

Medigap plans provide critical financial coverage, but only if you act at the right time. Your six-month Medigap Open Enrollment Period is the most opportune moment to secure coverage without worrying about your health history. After that, the window narrows significantly.

If you’re turning 65 or newly enrolled in Medicare Part B in 2025, don’t delay your decision. Planning ahead and understanding your timeline can save you money and stress down the road.

Need guidance? Talk to a licensed agent listed on this website to make a confident, well-timed decision about your Medigap coverage.