Keep in mind that if you drop your Medigap policy, in most cases you won't be able to get it back, so pay attention to the timing. In general, you can only join a Medicare Advantage Plan during the Medicare Open Enrollment Period between October 15 – December 7 each year.
Medicare Advantage plans are difficult to budget, and most plans have high out-of-pocket costs. This is the biggest reason they are bad for some people. With Original Medicare and supplemental Medicare insurance, you pay the bulk of your major medical costs upfront through monthly insurance premiums.
You can switch to a Medicare Advantage plan from Original Medicare during the Annual Enrollment Period each fall, October 15 through December 7.
If you have extensive medical needs, you may save money with a Medicare Supplement plan. But if your health issues are pretty minor, a Medicare Advantage plan may give you sufficient coverage at a more affordable price.
If you are age 65 or over and eligible for Medicare, you have a 6-month period during which you can purchase almost any Medigap policy at the lowest price for your age, even if you have or recently had health problems.
In general, you can only join a Medicare Advantage Plan during the Medicare Open Enrollment Period between October 15 – December 7 each year. If you join during Open Enrollment, your Medicare Advantage Plan coverage will begin on January 1. Contact your Medigap insurance company to cancel your Medigap policy.
There are 10 different types of Medigap policies (labeled A through N), each having a different, standardized set of benefits (Appendix Table 3). Plan G is the most popular Medigap policy, accounting for 39% of all policyholders, or nearly 5.3 million people, in 2023 (Figure 3).
In contrast, Medicare Supplement plans offer predictability, ease of use, and broader access to care, making them a preferred option for many physicians. If you're weighing your Medicare options, consider not just the cost but also how your choice could impact your access to care.
Medicare Advantage offers extra benefits, but out-of-network care may be limited or costly. Other disadvantages include difficulty switching out of the plans later, restrictions on care access, and limitations on extra benefits.
Best Medicare Supplement for seniors and retirees: AARP/UnitedHealthcare. AARP/UnitedHealthcare is the best company for Medigap plans in 2026. For most people, the best company for Medigap coverage is AARP/UnitedHealthcare.
The most common reason that doctors may discontinue their acceptance of Medicare Advantage is that the private insurance company makes it difficult or time-consuming for the doctor to get paid for their services.
Short Answer
You can apply for a new Medicare supplement insurance policy at any time. However, medical underwriting may apply and you may be denied coverage due to health conditions. Each year, during the Annual Enrollment Period from October 15 to December 7, you can enroll in a Medicare Advantage plan.
Medicare Advantage Plans can deny coverage for various reasons, such as pre-existing conditions, not meeting enrollment criteria, or if the plan does not operate in your area.
Medicare Advantage members are most likely to disenroll from their health plan because of four main reasons: difficulty accessing care, low plan generosity, dissatisfaction with care quality, and the type of plan (HMO vs. PPO), according to a June study published in Health Affairs.
For comparison, the Centers for Medicare and Medicaid Services completed almost 400,000 prior authorization reviews for Original Medicare in 2023 and denied 28.8%, or 113,448 of requests received. Centene and CVS Health Medicare Advantage plans had the highest denial rates for prior authorization requests.
If you joined a Medicare Advantage Plan during your Initial Enrollment Period, you can change to another Medicare Advantage Plan (with or without drug coverage) or go back to Original Medicare (with or without a drug plan) within the first 3 months you have Medicare Part A & Part B.
Across the country, health systems report that Medicare Advantage's growing administrative burden — from denied authorizations to delayed reimbursements — has become unsustainable. Some hospitals have already ended their contracts; others are limiting participation to only a few select plans.
Medicare Advantage Plan (Part C):
Deductibles, coinsurance, and copayments vary based on which plan you join. Plans also have a yearly limit on what you pay out-of-pocket. Once you pay the plan's limit, the plan pays 100% for covered health services for the rest of the year.
Other benefits: Original Medicare does not cover vision, hearing, or dental services. Medicare Advantage plans may cover additional services, including vision, hearing, and/or dental, but those additional benefits may increase your premium and/or other out-of-pocket costs.
Medigap & Medicare Advantage Plans
When you're getting started with Medicare, you can either buy Medigap or enroll in a Medicare Advantage Plan, but you can't have both. You can't buy Medigap while you're in a Medicare Advantage Plan unless you're switching back to Original Medicare.
UnitedHealth Group is dropping some of its Medicare Advantage plans. UnitedHealth Group announced last month that it plans to drop 1 million Medicare Advantage members.
UnitedHealthcare is the largest company selling Medicare Advantage plans [1] . UnitedHealthcare also partners with AARP, insuring the Medicare products that carry the AARP name. UHC offers $0-premium plans in 45 states — the most offered by any Medicare Advantage company in 2026, tied with Humana.
Medicare Supplement Plans F, G, and N have different cost structures, which can impact your out-of-pocket expenses. Plan F typically has the highest premium among the three plans, but it offers the most comprehensive coverage, including coverage for Medicare Part B excess charges.
Here are some of the biggest Medicare mistakes to avoid:
UnitedHealthcare gets slightly higher overall star ratings than BCBS and may offer lower prices, but BCBS might offer a better customer experience.