Medicare Advantage plans currently enrol approximately 55% of all Medicare-eligible Americans, drawn in by the promise of $0 monthly premiums, vision and dental coverage, fitness memberships, and other extra benefits that Original Medicare does not include. These benefits are real. The trade-offs are also real — and less clearly advertised. This guide lays out both sides honestly so you can make the choice that is right for your health and finances in 2026.
The Fundamental Structural Difference
Original Medicare (Parts A and B) is administered directly by the federal government. It covers hospitalisation and medical services for anyone enrolled. Medicare Advantage (Part C) contracts with private insurance companies — UnitedHealthcare, Humana, Aetna, BCBS affiliates — who administer your benefits in exchange for a fixed payment from CMS per enrollee.
This structural difference drives most of the practical differences you experience as a patient. The private insurer has an incentive to manage costs through network restrictions, prior authorization, and clinical criteria that standard Medicare does not impose. The federal government, administering traditional Medicare, has no equivalent incentive.
The Real Cost Comparison
| Factor | Medicare Advantage (typical) | Original Medicare + Medigap Plan G |
|---|---|---|
| Monthly premium | $0–$50 (plan premium) | $185 Part B + $100–$200 Medigap |
| Annual deductible | $0–$500 (varies by plan) | $257 Part B deductible (Plan G covers Part A deductible) |
| Out-of-pocket maximum | $3,000–$8,850 in-network | Near zero after Medigap (most costs covered) |
| Prior authorization required | Yes — extensively | No — very rarely required |
| Provider network | Restricted to plan network | Any provider accepting Medicare (vast majority) |
| Referrals required | Often (HMO plans) | No referrals needed |
| Out-of-network coverage | Limited or none (HMO) | Any Medicare-accepting provider nationwide |
| Denial rate (prior auth) | 12.8% (UHC); varies by plan | Denials rare; no prior auth for most services |
| Extra benefits (dental/vision) | Often included | Not included — must purchase separately |
The critical insight in this table: Medicare Advantage’s lower premium is real, but the out-of-pocket maximum can be 10 times higher than what you would pay with Original Medicare plus Medigap. For someone who stays healthy and uses minimal care, Advantage often costs less. For someone with a serious illness, hospitalisation, or complex ongoing treatment, the out-of-pocket costs under Advantage can be dramatically higher than the premium savings.
Prior Authorization: The Hidden Administrative Burden
Original Medicare does not require prior authorization for most services. If your physician orders a procedure and Medicare covers it, it is covered. Medicare Advantage plans routinely require prior authorization for specialist visits, surgeries, advanced imaging, post-acute care placements, and many medications. This is the practical difference most people do not understand until they need care.
In 2026, Medicare Advantage plans collectively denied approximately 4.1 million prior authorization requests. UnitedHealthcare denied 12.8% of PA requests in its Medicare Advantage plans. The Senate Permanent Subcommittee on Investigations documented that AI algorithms — not physician reviewers — generated many of these denials. And 80.7% of denials were overturned when patients appealed. But the vast majority of patients did not appeal.
The prior authorization burden affects the most vulnerable enrollees most — those who need frequent specialist care, those being discharged from a hospital to a rehabilitation facility, and those managing complex chronic conditions that require ongoing specialist management.
The Network Problem
Medicare Advantage plans contract with a specific set of providers. Your current doctors may or may not participate. If they do not, you either pay significantly more out-of-network (if your plan covers it at all) or you switch doctors.
In 2026, approximately 2.9 million Medicare Advantage enrollees were displaced into new plans following plan exits and service area reductions by major insurers. Many of these enrollees found that their new plan did not include their existing physicians — creating care disruptions for patients with established specialist relationships. This is a risk that does not exist with Original Medicare, where any physician who accepts Medicare is accessible to you.
When Medicare Advantage Makes Sense
Medicare Advantage is genuinely the better choice for some people:
- If you are relatively healthy and expect limited healthcare utilisation — the lower premium and extra benefits represent real value if you rarely need the plan’s services.
- If dental and vision coverage is a priority — Original Medicare does not cover routine dental, hearing, or vision care. Medigap does not either. If you cannot separately afford these, Advantage’s extra benefits have meaningful value.
- If all your preferred doctors are in the plan’s network — verify this before enrolling, and reverify annually as networks change.
- If you have limited income and cannot afford Medigap premiums — Advantage’s $0 premium makes coverage accessible when Medigap premiums would not be.
Can You Switch? The Medigap Timing Problem
You can switch from Medicare Advantage to Original Medicare during the Annual Enrollment Period (October 15–December 7) or the Medicare Advantage Open Enrollment Period (January 1–March 31). The complication: if you want to add Medigap coverage when you switch, most states allow insurers to medically underwrite Medigap plans outside of your initial enrollment window. This means pre-existing conditions can affect your access to or pricing of Medigap — potentially making the switch much more expensive than it would have been at age 65.
The implication: your most important Medicare decision is the one you make at 65, during the 6-month Medigap Open Enrollment Period when you first enrol in Part B. Medigap must accept you at standard rates during this window regardless of health history. After it closes, switching is significantly more complicated.
