IRMAA Basics
Comparing Medicare Supplement Insurance and Medicare Advantage Plans
Verified against SSA POMS as of September 17, 2026
The short answer
Medicare Supplement Insurance (Medigap) and Medicare Advantage Plans (Part C) serve different purposes in Medicare coverage: Medigap covers costs not included in Original Medicare, such as deductibles and coinsurance, while Medicare Advantage offers an alternative to Original Medicare, often with additional benefits and managed care options. Medigap is used alongside Original Medicare, whereas you cannot have both Medigap and Medicare Advantage at the same time.
Medicare Supplement Insurance Coverage
Medicare Supplement Insurance, also known as Medigap, is a policy that you can buy to cover out-of-pocket costs not covered by Original Medicare, such as Part A and Part B coinsurance, copays, and deductibles. Medigap plans provide predictable medical spending and shield you from significant medical bills. To purchase a Medigap policy, you must be enrolled in Medicare Part A and Part B. Each Medigap policy only covers one person and standardized plans are identified by letters (A, B, C, D, F, G, K, L, M, N). Premiums are separate from Part B premiums and these policies can't be combined with Medicare Advantage plans. Medigap does not include prescription drug coverage; to have drug coverage, a separate Medicare Part D plan is needed.
CMSPDF:medicare/health-plans/medigap/downloads/frn_naic_03_25_05.pdf View source ›Medicare Advantage Plans Features
Medicare Advantage Plans (Part C) provide an alternative way to receive Medicare benefits through private health plans approved by Medicare. These plans must include all services covered under Original Medicare and often offer additional benefits such as dental care, wellness programs, and prescription drug coverage. Medicare Advantage Plans usually have low monthly premiums and are particularly suitable for individuals in good health who intend to use in-network doctors. These plans may have different rules, costs, and coverage restrictions, including network providers, and have a yearly limit on out-of-pocket expenses. Types of plans include Health Maintenance Organizations (HMOs), Preferred Provider Organizations (PPOs), Private Fee-For-Service Plans, and others.
MCR:basics/get-started-with-medicare/get-more-coverage/your-coverage-options/compare-original-medicare-medicare-advantage View source ›Eligibility and Enrollment Considerations
To enroll in a Medigap plan, individuals must have Original Medicare (Part A and B). Enrollment into a Medigap policy is open during the first 6 months after turning 65 and enrolling in Part B. If you have Medicare Advantage, you cannot enroll in Medigap. Medicare Advantage Plans can be joined or switched during specified enrollment periods, such as the annual Open Enrollment Period from October 15 to December 7 each year.
MCR:health-drug-plans/open-enrollmentKey Differences in Coverage
Medicare Advantage Plans often provide a bundle of Medicare Part A, Part B, and usually Part D coverage in one plan, while Medigap policies complement Original Medicare by filling in benefit gaps. Medigap policies do not cover vision, dental, and long-term care, unlike some Medicare Advantage plans, which might offer these additional services.
MCR:health-drug-plans/medigap/basics/how-medigap-works View source ›Frequently asked
Can you have both Medicare Advantage and Medigap?
No, you cannot have both a Medicare Advantage Plan and a Medigap policy at the same time. Medigap is designed to supplement Original Medicare, whereas Medicare Advantage plans replace Original Medicare coverage. However, it is important to note that you must first sign up for Original Medicare (Parts A and B) before enrolling in either a Medicare Advantage Plan or a Medigap policy.
Do Medicare Advantage plans cover prescription drugs?
Yes, most Medicare Advantage plans include Part D prescription drug coverage. However, coverage details can vary by plan. If an individual is not utilizing a Medicare Advantage plan and is instead using Original Medicare, they must purchase a standalone Part D plan to have outpatient drug insurance.
What does a Medigap policy cover?
Medigap policies cover out-of-pocket costs not paid by Original Medicare, such as copayments, coinsurance, and deductibles. Policies sold after 2005 do not include prescription drug coverage.
What is the difference between Original Medicare and Medicare Advantage?
Original Medicare covers hospital and medical services (Part A and B). In contrast, Medicare Advantage plans (Part C) offer an alternative that bundles these services and often includes additional benefits, such as drug coverage. Most Medicare Advantage plans include drug coverage, which is not provided by Original Medicare. If you are using Original Medicare and wish to have outpatient drug insurance, you must purchase a standalone Part D plan.
Are there significant premium differences between Medicare Advantage and Medigap plans?
Generally speaking, yes. Medicare Advantage (MA) premiums are usually less than $100 per month, while Medigap plans average between $100-$300 per month. Most MA plans include drug coverage. However, if you are not utilizing MA and are instead using original Medicare, you must purchase a standalone Part D plan if you wish to have outpatient drug insurance, as Medigap does not provide drug coverage.
What is the out of pocket cost difference between MA Plans and Medigap?
Medigap plans pay virtually all costs above what Medicare A and B will pay. The one exception is the Part B deductible paid by the beneficiary, which is $283 in 2026. Medigap fills the cost gaps of Original Medicare including copays and co-insurance. MA plans cost share with beneficiaries. The federal limit for in network out of pocket expenses can not exceed $9,250. Most MA plans have lower out of pocket annual limits, but they are still significant.