Choosing how to receive Medicare coverage affects provider access, out-of-pocket exposure, drug coverage, prior authorization and travel. The best fit depends on individual circumstances, but the structural differences are clear enough to compare before enrollment.
How Original Medicare plus Medigap works
Original Medicare includes Part A and Part B. Medicare pays its share of covered services and the beneficiary is responsible for applicable deductibles, coinsurance and other cost sharing. A Medigap policy can help pay some of those remaining costs according to the standardized plan benefits.
Medicare.gov explains that Medigap is extra insurance sold by private companies. In most states, standardized plans are identified by letters. Plans with the same letter provide the same standardized core benefits even though premiums can differ by insurer.
How Medicare Advantage works
Medicare Advantage plans are Medicare-approved private plans that provide Part A and Part B benefits as an alternative to Original Medicare. Plans must cover medically necessary services that Original Medicare covers and can provide additional benefits. Most Medicare Advantage plans include Medicare drug coverage (Part D).
Networks, referrals and prior authorization can apply. Plan rules and benefits vary by service area and can change from year to year within Medicare requirements.
| Feature | Original Medicare + Medigap | Medicare Advantage |
|---|---|---|
| How Medicare coverage is delivered | Original Medicare, with a separate supplement | Private Medicare-approved Part C plan |
| Provider access | Any doctor or hospital that accepts Medicare, subject to Medicare rules | Network and service-area rules may apply |
| Prior authorization | Usually not required for most Original Medicare services | May be required for certain services |
| Annual out-of-pocket limit for covered Medicare services | Original Medicare itself has no annual limit; Medigap can reduce cost sharing | Plans have a yearly limit for covered Medicare services |
| Drug coverage | Separate Part D plan can be added | Most plans include Part D |
| Can Medigap be used? | Yes, with Original Medicare if eligible | No, not to cover Medicare Advantage cost sharing |
Provider networks and travel
With Original Medicare, beneficiaries can generally use any doctor or hospital in the United States that takes Medicare. Medicare Advantage plans may require in-network providers for non-emergency care, although some plans provide out-of-network benefits.
Original Medicare generally does not cover routine care outside the United States. Some Medigap plans include limited foreign-travel emergency benefits. Medicare Advantage plans generally do not cover routine care outside the U.S., though some may offer emergency or urgent-care travel benefits. Check the actual plan.
Out-of-pocket costs
Original Medicare generally leaves Part A and Part B cost sharing. Medigap can cover some of those amounts based on the plan letter. Medicare Advantage plans use their own copays, coinsurance and deductibles and are required to have a yearly maximum for covered Medicare services.
Comparisons should include premiums as well as expected medical use. A low-premium option is not automatically the lowest total annual cost.
Prescription drugs
Medigap policies sold after 2005 do not include prescription-drug coverage. A person using Original Medicare and Medigap can generally enroll separately in Part D. Most Medicare Advantage plans include Part D, although plan structures vary.
Enrollment timing matters for Medigap
Medigap purchasing rights can depend on timing, age, state law and guaranteed-issue protections. Outside protected enrollment periods, medical underwriting may be permitted in some circumstances. Medicare.gov notes that availability for people under 65 can also differ by state. Do not assume you can always move from Medicare Advantage to any Medigap policy later without eligibility or underwriting issues.
Questions to compare before enrolling
- Are my doctors, hospitals and specialists available under the option?
- How often do I travel or live in more than one state?
- What are the premiums plus likely deductibles, copays and coinsurance?
- Are my prescriptions on the plan formulary and what would they cost?
- Which services require prior authorization or referrals?
- If considering Medigap, am I in a protected enrollment or guaranteed-issue period?
- How could the plan’s annual out-of-pocket limit affect a high-cost year?
Frequently asked questions
Can I have Medigap and Medicare Advantage at the same time?
Medigap is designed to supplement Original Medicare. You cannot use it to pay Medicare Advantage copayments, deductibles or premiums.
Does Medicare Advantage replace Medicare?
No. It is a Medicare-approved way to receive Medicare-covered services through a private plan while remaining enrolled in Medicare.
Does Medigap include prescription drugs?
New Medigap policies do not include drug coverage. A separate Part D plan can be used with Original Medicare.
Are Medigap benefits identical from every company?
In most states, plans are standardized by letter, so the benefits for the same plan letter are standardized, although premiums and service can differ. Massachusetts, Minnesota and Wisconsin use different standardization systems.
Sources & further reading
Reviewed October 2, 2026 using Medicare.gov. Medicare plan availability, premiums, networks and enrollment rights can change and can vary by location; use Medicare.gov and official plan documents for current decisions.
