Medigap • Medicare Supplement Insurance
What Is Medigap and How Does Medicare Supplement Insurance Work?
A clear, calm guide to how Medigap works with Original Medicare, what it may help pay, and what to verify before you apply.
Medigap—also called Medicare Supplement Insurance—is private insurance that works with Original Medicare. Original Medicare pays first for covered Part A and Part B services. Your Medigap policy may then pay some of the deductibles, copayments, or coinsurance left to you, according to the benefits in your policy. Medigap does not replace Original Medicare.
Start with Original Medicare
Medigap supplements Original Medicare. It does not supplement Medicare Advantage.
Medigap only makes sense after you understand the coverage it supplements. Original Medicare includes Part A and Part B, and it pays its share of approved amounts for covered services.
Original Medicare does not place one annual limit on everything you may pay out of pocket. Depending on the service, you may be responsible for deductibles, copayments, or coinsurance. A Medigap policy is designed to help with certain gaps in that cost sharing.
To buy a Medigap policy, you generally need both Medicare Part A and Part B. You keep Original Medicare, show your Medicare card when you receive covered care, and pay a separate premium to the private insurance company for the Medigap policy.
How does Medigap work?
For a Medicare-covered service, Original Medicare generally processes the claim first. Medicare pays its share, and the Medigap policy may then pay its share based on the standardized benefits included in your plan letter.
A Medigap policy covers one person. Spouses need separate policies. The policy is guaranteed renewable as long as you pay the premium, which generally means the insurance company cannot cancel it just because your health changes.
Plain-English distinction: Medicare remains responsible for deciding whether a service is covered under Original Medicare. Medigap helps with specified cost sharing; it does not turn a noncovered service into a covered one.
What can Medigap help pay?
The exact benefits depend on the standardized plan letter you buy. Depending on the letter and when you first became eligible for Medicare, a Medigap policy may help pay some or all of these Original Medicare gaps:
- Part A hospital coinsurance and certain additional hospital costs.
- Part B coinsurance or copayments.
- The first three pints of blood used in an approved medical procedure.
- Part A hospice care coinsurance or copayments.
- Skilled nursing facility care coinsurance.
- The Part A deductible.
- Limited foreign travel emergency benefits under certain plan letters.
Not every plan letter covers every item, and federal law limits who can buy plans that cover the Part B deductible. Use the current official plan-benefit chart before relying on a general summary.
What does Medigap generally not cover?
Medigap is not comprehensive coverage for every healthcare or long-term support need. Medigap policies generally do not cover:
- Long-term custodial care.
- Routine dental or vision care.
- Hearing aids.
- Eyeglasses.
- Private-duty nursing.
Policies sold after 2005 generally do not include outpatient prescription drug coverage. If you want drug coverage while using Original Medicare and Medigap, you may need a separate Medicare Part D plan.
Are Medigap plans standardized?
In most states, Medigap policies are standardized by letter. Plans with the same letter include the same standardized core benefits, regardless of which insurance company sells the policy. For example, the benefits in one company’s Plan G follow the same federal standard as another company’s Plan G.
That does not mean every company charges the same premium or provides the same customer experience. Premiums, available discounts, underwriting practices where permitted, service, and local availability can differ.
Three-state exception: Massachusetts, Minnesota, and Wisconsin standardize Medigap policies differently. If you live in one of those states, use the official materials for your state rather than assuming the lettered-plan structure applies in the same way.
What is Medicare SELECT?
Medicare SELECT is a type of Medigap policy that may require you to use certain hospitals and, in some cases, certain doctors for full benefits except in an emergency. Availability and network rules depend on the policy and location, so verify the details before enrolling.
What does a Medigap policy cost?
You pay the private insurance company a monthly premium for Medigap in addition to your Medicare Part B premium and any Part D premium. The premium can vary based on the company, location, plan letter, rating method, age where permitted, discounts, and other factors allowed under state law.
Two policies with the same letter provide the same standardized benefits in most states, but they may have very different premiums. Premiums may also rise over time. Compare the long-term cost structure—not only the price when you first apply.
Medigap and Medicare Part D are separate
Modern Medigap policies do not bundle outpatient prescription drug coverage. Many people who use Original Medicare and Medigap choose a separate Part D plan, but the right decision depends on their medications, other creditable drug coverage, eligibility, and timing.
Drug plans have separate premiums, formularies, pharmacy networks, and enrollment rules. Review the Medicare Part D foundation before deciding how you will handle prescription coverage.
Medigap is not Medicare Advantage
| Medigap | Medicare Advantage |
|---|---|
| Works with Original Medicare and may pay specified Original Medicare cost sharing. | Is another way to receive Part A and Part B benefits through a Medicare-approved private plan. |
| Does not replace Original Medicare. | The plan generally becomes the primary way you receive most Medicare-covered healthcare while you remain enrolled in Medicare. |
| Generally does not include modern Part D drug coverage. | Many plans include Part D drug coverage. |
| Generally allows you to see any provider nationwide who accepts Medicare, except some Medicare SELECT policies. | May use provider networks, referrals, prior authorization, and plan-specific rules. |
You cannot use Medigap to pay Medicare Advantage deductibles, copayments, or coinsurance. If you need the Medicare Advantage foundation first, read What Is Medicare Advantage? When you are ready to compare the two coverage paths, use the reviewed subordinate guide: Medicare Advantage vs. Medigap.
When is the best time to buy Medigap?
Your strongest federal buying protection is generally your one-time Medigap Open Enrollment Period. For people age 65 or older, it lasts six months and begins the first month you have Medicare Part B.
During that period, an insurance company generally cannot use medical underwriting to deny you a Medigap policy available for sale, charge you more because of health problems, or make you wait for coverage of a pre-existing condition beyond the limits Medicare allows.
Do not confuse this with Medicare’s annual Open Enrollment Period. Medicare Open Enrollment runs each fall for Medicare Advantage and Part D changes. It does not create a new federal Medigap Open Enrollment Period every year.
If you delayed Part B because you had active employer coverage, your Medigap Open Enrollment timing may begin when your Part B coverage starts at age 65 or older. Verify your Part B effective date and individual circumstances before relying on a deadline.
Can you buy or switch Medigap later?
You may apply later, but applying is not the same as being approved. Outside your Medigap Open Enrollment Period or a protected right, an insurance company may use medical underwriting where state law permits. That may affect whether you are accepted, how much you pay, or whether you can get the policy you want.
Federal guaranteed-issue rights apply in certain defined situations, and some states provide additional protections. The facts, documentation, dates, current coverage, and policy availability all matter.
- If you already have Medigap, review whether you can switch Medicare Supplement plans.
- If your question is specifically about health questions or protected rights, review switching Medigap without underwriting.
- If you heard about a birthday or anniversary opportunity, use the state-qualified Medicare Birthday Rule guide and confirm the current rule with your state regulator.
Never cancel existing coverage until you have written confirmation that the new coverage is approved and you understand its effective date.
Why state rules matter
Federal Medigap rules provide the national foundation, but state law can materially change the answer. State rules may affect Medigap availability for people under 65, additional guaranteed-issue rights, birthday or anniversary protections, underwriting limits, premium-rating rules, and which policies are sold.
If you have Medicare before age 65 because of disability, End-Stage Renal Disease, or ALS, do not assume the same Medigap choices and prices available at age 65 apply to you. Check with your State Insurance Department and your local State Health Insurance Assistance Program (SHIP).
If you live in Florida and have already completed the national foundation, you may continue to the Florida Medigap comparison guide.
What should you verify before applying?
- Confirm your Medicare Part A and Part B effective dates.
- Determine whether you are in your Medigap Open Enrollment Period or have a guaranteed-issue right.
- Check your state’s current Medigap protections and under-65 rules if relevant.
- Confirm which standardized plan letters and companies are available where you live.
- Compare premiums, rating methods, potential increases, and available discounts.
- Review the exact standardized benefits and any Medicare SELECT network rules.
- Plan separately for prescription drug coverage if you need Part D.
- Confirm the policy’s effective date in writing.
- Keep existing coverage until the new policy is approved and active.
Where to go next
Your next step depends on the question you still need answered:
- Need the prerequisite? Review Original Medicare.
- Need separate outpatient prescription coverage? Learn how Medicare Part D works.
- Comparing coverage paths? Read Medicare Advantage vs. Medigap.
- Concerned about timing or health questions? Use the exact switching or underwriting guide above, then verify with official sources.
- Need state-specific rules? Contact your State Insurance Department or SHIP.
Official Medicare sources
- Medicare.gov: Medicare Supplement Insurance (Medigap)
- Medicare.gov: Get Medigap basics
- Medicare.gov: How Medigap works
- Medicare.gov: Compare Medigap plan benefits
- Medicare.gov: When to buy a Medigap policy
- Medicare.gov: Choosing a Medigap Policy guide
Want Help Reviewing Your Medicare Options?
Once you understand the coverage path and have verified the timing and state rules that apply, Robin can help you review the Medicare options she is licensed and authorized to offer in your area. RobinsWisdom does not offer every plan available in every area.
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Robin Dall
Florida Medicare Broker & Educator
Robin Dall is a Florida Licensed Life, Health & Annuity Agent and founder of RobinsWisdom. This article was researched, written, and reviewed by Robin and reflects Medicare rules and guidance available at the time of publication.
About Robin Dall →Reviewed for accuracy: August 7, 2026. This article provides general Medicare education. Policy availability, premiums, underwriting, guaranteed-issue rights, state protections, and individual eligibility can vary. Confirm current rules and your exact circumstances before applying or changing coverage.
