6 Medicare Advantage Surprises That Could Cost You Thousands

Medicare Advantage — the private insurance alternative to Original Medicare — now covers more than half of all Medicare beneficiaries, and it's easy to see the appeal. Many plans advertise $0 premiums, dental and vision benefits, and gym memberships. But the fine print contains several features that can turn a seemingly great deal into a costly mistake. Understanding these less-discussed realities before you enroll — or before you decide to stay — can protect both your health and your wallet.

The first thing many beneficiaries don't realize is that Medicare Advantage plans operate on networks, and those networks can change every single year. Unlike Original Medicare, which lets you see virtually any doctor or hospital in the country that accepts Medicare, a Medicare Advantage HMO or PPO restricts you to a defined list of providers. In 2025, CMS data shows that HMO-style plans make up the majority of Medicare Advantage enrollment. If your cardiologist, oncologist, or primary care physician drops out of your plan's network mid-year — which plans are permitted to do — you may face significantly higher out-of-pocket costs or need to find a new provider entirely. Before enrolling, always verify that your specific doctors and your preferred hospital are listed as in-network for the coming plan year, not just the current one.

The second surprise involves prior authorization — a process where your plan must approve certain procedures, medications, or specialist visits before you receive them. Original Medicare does not require prior authorization for most services. Medicare Advantage plans, however, use it extensively. A 2022 report from the HHS Office of Inspector General found that Medicare Advantage plans denied 13% of prior authorization requests that met Medicare coverage rules — meaning care that Original Medicare would have paid for was initially blocked. While many denials are eventually overturned on appeal, the process takes time, and delays in care for conditions like cancer, heart disease, or orthopedic injuries can have real health consequences. When comparing plans, ask specifically which services require prior authorization and how long the plan's standard review process takes.

Third, the out-of-pocket maximum in Medicare Advantage is not as protective as it sounds. In 2025, the maximum out-of-pocket limit for in-network services is $9,350, and for combined in-network and out-of-network costs in PPO plans, it can reach $14,000. But here's the critical detail: that cap applies only to Medicare Parts A and B services — hospital and medical care. It does not cap your Part D prescription drug costs. If you take expensive specialty medications, your drug costs can stack on top of that $9,350 ceiling. The Inflation Reduction Act did introduce a $2,000 annual cap on out-of-pocket Part D drug costs starting in 2025, which is meaningful relief. But that's still a potential combined exposure of over $11,000 in a bad year — far more than many beneficiaries budget for.

Fourth, many beneficiaries don't understand the difference between extra benefits that are truly included and those that come with significant limitations. Dental coverage in Medicare Advantage plans is a prime example. A plan may advertise dental benefits, but the actual coverage often applies only to preventive care — cleanings, X-rays, and exams — with a separate annual maximum, often $1,000 to $2,000, for more extensive work like crowns, root canals, or dentures. A crown alone can cost $1,500 or more. Vision benefits similarly may cover only one routine eye exam per year and a modest allowance toward frames or contacts. Hearing aid allowances, where offered, typically range from $500 to $2,500 per ear every two to three years — helpful, but not full coverage when quality hearing aids can cost $3,000 to $7,000 per pair. Always read the Summary of Benefits document, not just the marketing materials.

Fifth — and this one catches people off guard — getting back to Original Medicare after leaving it for Medicare Advantage is harder than most people expect. When you first turn 65 or enroll in Medicare, you have a guaranteed issue right to buy a Medigap (Medicare Supplement) policy, meaning insurers cannot reject you or charge you more based on your health. But once that initial window closes, most states allow Medigap insurers to use medical underwriting. That means if you've been on a Medicare Advantage plan for several years and want to switch back to Original Medicare with a Medigap policy, you could be denied coverage or charged higher premiums because of conditions like diabetes, heart disease, or a prior cancer diagnosis. There is a limited exception: if you joined Medicare Advantage for the first time and switch back within 12 months, you retain guaranteed issue rights. A handful of states — including California, New York, Oregon, and Illinois — have birthday rules or continuous open enrollment laws that provide additional Medigap switching protections. If you live outside those states, think carefully before leaving Original Medicare, because returning with full Medigap coverage may not be possible.

Sixth, the star ratings system that CMS uses to grade Medicare Advantage plans — on a scale of one to five stars — is a useful tool, but it measures plan administration and member satisfaction more than it measures clinical outcomes for complex patients. A plan can earn four or five stars for timely customer service, appeals processing, and preventive care screenings while still having a narrow network, aggressive prior authorization policies, or limited specialist access. High-star plans do tend to offer more stable benefits and better member experiences, and CMS does provide bonus payments to high-rated plans that can fund richer benefits. But a five-star rating should be one factor in your decision, not the deciding one. Cross-reference the star rating with the plan's provider directory, its formulary for your specific medications, and its prior authorization requirements for any conditions you currently manage.

If you're evaluating Medicare Advantage plans for 2026 or reconsidering your current coverage, the Annual Enrollment Period runs October 15 through December 7 each year, with changes taking effect January 1. If you're already in a Medicare Advantage plan and want to switch to a different Advantage plan or return to Original Medicare, the Open Enrollment Period runs January 1 through March 31. Use Medicare's Plan Finder tool at Medicare.gov to compare plans side by side using your actual zip code, doctors, and drug list. Your State Health Insurance Assistance Program — known as SHIP — offers free, unbiased counseling from trained advisors who can walk you through plan comparisons without trying to sell you anything. Find your local SHIP counselor at shiphelp.org.