Medicare Advantage plans come with real trade-offs that aren’t obvious from the TV commercials promoting $0 premiums and extra benefits. The biggest downsides are restricted provider networks, prior authorization requirements that can delay or deny care, limited access to top specialists, and the difficulty of switching back to Original Medicare once you’ve enrolled. These drawbacks can be minor inconveniences for healthy enrollees but serious problems for people with complex medical needs.
Restricted Provider Networks
Original Medicare lets you see any doctor or visit any hospital in the country that accepts Medicare. Medicare Advantage works differently. Most plans require you to use doctors and facilities within a specific network, and going out of network for non-emergency care either costs significantly more or isn’t covered at all.
HMO-style Medicare Advantage plans, which cover roughly half of all enrollees, generally provide zero coverage for out-of-network care unless it’s an emergency. PPO plans do allow out-of-network visits, but your cost sharing jumps considerably. If you have long-standing relationships with specific doctors, there’s no guarantee they’ll be in your plan’s network, and networks can change from year to year.
This also matters when you travel. Original Medicare covers you at any participating facility nationwide. With most Medicare Advantage plans, routine or planned care outside your plan’s service area isn’t covered.
Limited Access to Top Hospitals and Cancer Centers
Network restrictions hit hardest when it comes to specialized care. A KFF study of Medicare Advantage plan networks across 20 counties found that plans typically include only about half the hospitals in their area. One in five plans did not include any academic medical center in their network. Among plans in areas with a National Cancer Institute-designated cancer center, more than two in five (41%) did not include that cancer center.
For someone diagnosed with a rare or aggressive cancer, access to a top-tier cancer center can meaningfully affect treatment options. Being locked out of these facilities, or facing steep out-of-network charges to use them, is one of the most consequential downsides of Medicare Advantage.
Prior Authorization Delays and Denials
Medicare Advantage plans frequently require prior authorization before covering certain services. Your doctor’s office has to submit a request to the insurance company, which then decides whether the service is medically necessary. This process can delay MRIs, surgeries, rehabilitation stays, and other time-sensitive care.
A 2022 investigation by the HHS Office of Inspector General found that 13% of prior authorization denials by large Medicare Advantage organizations involved services that actually met Medicare’s coverage rules. These were services that would have been approved under Original Medicare. The denied services included advanced imaging like MRIs and post-acute care such as inpatient rehabilitation stays. Original Medicare does not use prior authorization for most services.
Starting in 2026, new federal rules will require Medicare Advantage plans to process prior authorization requests within 7 calendar days, down from the previous 14-day window. That’s an improvement, but a week-long wait can still be stressful when you’re dealing with a serious diagnosis.
Cost Sharing for Serious Illness
Medicare Advantage plans do offer something Original Medicare lacks: an annual out-of-pocket maximum. In 2025, that cap can be as high as $9,350 for in-network services and $14,000 when out-of-network services are included. While having any cap is better than none, reaching those limits still represents a significant financial hit.
The real cost pressure shows up with expensive treatments. For high-cost Part B drugs like cancer medications, in-network cost sharing is capped at 20% coinsurance (the same as Original Medicare). But if you receive care out of network, the picture changes dramatically. Among the millions of Medicare Advantage enrollees in PPO-type plans, close to half would be charged more than 20% for Part B drugs from an out-of-network provider. Some plans charge 40% or even 50% coinsurance for out-of-network drugs. And enrollees in HMO plans with no out-of-network coverage would pay 100% of the cost unless they got prior approval.
To put this in perspective, the average annual cost-sharing liability for the cancer drug Keytruda was $9,100 per beneficiary. For Darzalex, another cancer treatment, it was $12,900. These costs can accumulate quickly before you reach your plan’s out-of-pocket limit.
Supplemental Benefits Are Often Thinner Than Advertised
Dental, vision, and hearing coverage are major selling points for Medicare Advantage, since Original Medicare largely doesn’t cover these services. But the actual coverage is frequently more limited than ads suggest.
Among enrollees with extensive dental coverage through Medicare Advantage, 78% are in plans with annual dollar limits, averaging $1,300 per year. More than half are in plans that cap dental benefits at $1,000 or less. That can cover cleanings and basic fillings, but a single crown or root canal can easily exceed the annual limit, leaving you to pay the rest. Vision coverage for eyeglasses and contacts is universally subject to annual dollar caps as well.
These benefits aren’t worthless, but they’re far less generous than many enrollees expect when they sign up. A $1,000 dental cap doesn’t go far if you need significant dental work.
Plan Instability From Year to Year
Medicare Advantage plans are offered by private insurers, and those insurers can change benefits, adjust networks, raise costs, or exit your area entirely. At the end of 2025, 2.6 million people had their Medicare Advantage plan terminated as insurers discontinued plans or reduced their service areas. That affected 13% of all enrollees in individual Medicare Advantage prescription drug plans.
When your plan disappears, you have to find a new one during open enrollment. Nearly all affected beneficiaries (98.9%) had at least one other Medicare Advantage plan available, but “available” doesn’t mean equivalent. Your new plan might have a different network, different cost sharing, and different benefits. You may need to find new doctors. For someone managing ongoing treatment, this kind of disruption can be more than an inconvenience.
Switching Back to Original Medicare Is Risky
Perhaps the least understood downside is how difficult it can be to leave Medicare Advantage once you’ve joined. You can technically switch back to Original Medicare during open enrollment, but the practical barrier is Medigap coverage. Medigap (Medicare Supplement) policies fill in the gaps that Original Medicare leaves, covering deductibles and coinsurance. Most people on Original Medicare rely on a Medigap policy to keep costs predictable.
Here’s the problem: federal law only guarantees your right to buy a Medigap policy without medical underwriting during a limited window, typically the six months after you first enroll in Medicare Part B. If you spent those years in a Medicare Advantage plan and later want to switch to Original Medicare, insurers in most states can deny you a Medigap policy, impose waiting periods for pre-existing conditions, or charge significantly higher premiums based on your health. CMS and the National Association of Insurance Commissioners warn bluntly that “in most cases, if you drop your Medigap policy to join a Medicare Advantage Plan, you won’t be able to get it back.”
Only three states, Connecticut, Massachusetts, and New York, require insurers to sell Medigap policies to anyone at standard rates regardless of health status. Federal rules do provide limited “trial rights” for people who enrolled in Medicare Advantage when first eligible or who dropped Medigap to try Medicare Advantage for the first time, but only if they switch back within the first 12 months. There are also guaranteed-issue protections when a plan exits your market or your employer coverage ends. Outside those narrow circumstances, choosing Medicare Advantage can effectively become a one-way decision.
This lock-in effect means the stakes of your initial choice are higher than they appear. A plan that works well at 65, when you’re healthy and need little care, may become frustrating at 75 when you need specialists, expensive medications, or treatment at a major medical center. By then, returning to Original Medicare with affordable supplemental coverage may no longer be an option.