Updated November 2026 for the 2027 plan year. When you join Medicare, you choose between two paths. Original Medicare, usually paired with a Medigap supplement and a Part D drug plan, lets you see any doctor that takes Medicare nationwide and leaves you with predictable bills. Medicare Advantage, sold by private insurers, bundles hospital, medical and usually drug coverage into one plan with lower premiums, extra benefits and a provider network, but with prior authorization and out-of-pocket costs that can reach $9,850 in-network in 2027.
Medicare Advantage now covers most people with Medicare: 35.2 million, or 55% of those eligible, in 2026, according to KFF. About 12.9 million people had a Medigap policy in 2024.
Medigap vs Medicare Advantage Compared
| Feature | Original Medicare + Medigap + Part D | Medicare Advantage |
|---|---|---|
| Doctors and hospitals | Any provider nationwide that accepts Medicare | Plan network (HMO or PPO), usually local |
| Monthly premiums | Part B plus Medigap plus Part D premiums | Part B plus plan premium, often $0 |
| Out-of-pocket costs | Low and predictable with Plan G; no federal cap without Medigap | Copays up to the plan’s limit; up to $9,850 in-network for 2027 |
| Prior authorization | Rare | Common, especially for hospital stays and rehab |
| Extra benefits (dental, vision, hearing) | Not included | Often included, with limits |
| Travel | Coverage throughout the U.S.; some plans cover foreign emergencies | Emergency care anywhere; routine care usually in network only |
| Switching later | Easy to move to Medicare Advantage | Returning to Medigap may require medical underwriting |
The Decision That Is Hard To Undo
This is the part most people miss. You get one six-month Medigap open enrollment period, starting the month you are 65 or older and enrolled in Part B. During that window, insurers must sell you any Medigap policy at standard rates. After it ends, in most states, an insurer can deny you or charge more based on your health.
So a healthy 65-year-old who picks Medicare Advantage for the $0 premium may find, at 75 with a heart condition, that Medigap is no longer available. A trial right lets you return to Medigap within 12 months if you joined Medicare Advantage when first eligible.
A handful of states offer more protection. New York and Connecticut require year-round guaranteed issue, and 16 states, including California, Illinois and Oregon, have “birthday rules” or similar annual windows that let Medigap enrollees switch policies without underwriting, according to KFF. Those rules mostly help people already in Medigap, not those returning from Medicare Advantage.
Key Numbers for 2027
- Medicare Advantage in-network out-of-pocket limit: $9,850, up from $9,250 in 2026.
- High-deductible Medigap Plan G and Plan F deductible: $3,050, up from $2,950 (CMS).
- Medigap Plan K and Plan L out-of-pocket limits: $8,360 and $4,180.
- Part D base beneficiary premium: $41.33.
Who Each Option Suits
Medigap is often the better fit if you: travel or live in two states, want freedom to see specialists at major medical centers, have or expect serious health conditions, or want to avoid prior authorization.
Medicare Advantage is often the better fit if you: want the lowest monthly cost, are comfortable with a local network, value dental, vision and hearing benefits, or qualify for a special needs plan because you also have Medicaid.
Prior authorization is the sharpest trade-off. Medicare Advantage plans denied 65.3% of requests for long-term care hospital stays in a 2024 federal audit; see our Prior Authorization Report Card. Plan choices are also shrinking in many states for 2027, as our Medicare Advantage plans by state data shows.
How To Decide
- Price Medigap Plan G in your ZIP code at 65 and again at 75, using insurers’ published rates.
- Check whether your doctors and hospitals are in each Medicare Advantage network.
- Add premiums to the plan’s out-of-pocket maximum for a worst-case comparison.
- Read each plan’s prior authorization rules for hospital stays and rehabilitation.
- Get free help from your State Health Insurance Assistance Program (SHIP).
Higher-income enrollees also pay income-related surcharges on Part B and Part D under either path; see our IRMAA brackets guide. Follow our Medicare hub during Open Enrollment, which ends December 7.
Sources
KFF, Medicare Advantage in 2026 and Key Facts About Medigap Enrollment; CMS 2027 Medigap high-deductible and Plan K/L announcements; CMS final 2027 Medicare Advantage bid instructions; HHS Office of Inspector General, OEI-09-24-00330.