Almost everyone turning 65 has to pick one of two paths, and most people pick in a hurry, usually after a phone call from someone who earns a commission either way. This guide uses 2026 figures and tries to be straight with you about the parts that are genuinely hard to reverse later.
The two paths in one paragraph
Original Medicare is the government program. Part A covers hospital stays, Part B covers doctors and outpatient care, and you can see nearly any provider in the country who takes Medicare. It has no annual cap on what you can spend, so most people add a Medigap policy and a separate drug plan to close that hole. Medicare Advantage, also called Part C, is a private plan that takes over your Medicare benefits. It usually costs little or nothing extra each month, caps your yearly spending, and often throws in dental and vision. In return you use a network, and the plan gets to review whether your care is necessary before it pays. In 2026, 55% of eligible Medicare beneficiaries are enrolled in Medicare Advantage, so this is not a fringe choice either way.
How Original Medicare works: Parts A and B, plus a Medigap and Part D layer
Part A covers inpatient hospital care, skilled nursing after a hospital stay, hospice, and some home health. Most people pay no premium for it because they or a spouse paid Medicare taxes for at least 10 years. It does have a deductible, and it works per benefit period rather than per year. In 2026 the Part A deductible is $1,736 for each inpatient hospital benefit period, and a benefit period ends only after you have been out of a hospital or skilled nursing facility for 60 straight days. Go into the hospital twice in one year with a long gap between, and you pay it twice.
Part B covers everything outpatient: doctor visits, labs, imaging, surgery that does not require admission, and equipment like walkers and oxygen. The standard Part B premium is $202.90 a month in 2026, with a $283 annual deductible. After the deductible, Medicare pays 80% of the approved amount and you pay the other 20%.
That 20% is the problem. There is no ceiling on it. A cancer year or a bad cardiac year can run into five figures, and Medicare will keep paying its 80% forever while your 20% keeps growing.
Two add-ons close the gap. A Medigap policy (also called Medicare Supplement) is private insurance that pays your share of Medicare-covered costs. The plans are standardized by letter, so Plan G from one insurer covers exactly what Plan G from another covers, and the only real differences are price and service. Plan G is the common pick today: it covers your hospital deductible, your 20% coinsurance, and skilled nursing coinsurance, leaving you only the annual Part B deductible. Plan F covers even that, but it is closed to anyone who became eligible for Medicare on or after January 1, 2020. Premiums vary a lot by state, age, and insurer, so get real quotes rather than trusting an average.
Then you add a standalone Part D drug plan, since Original Medicare does not cover most prescriptions you fill at a pharmacy. Part D got much better recently. In 2026 your out-of-pocket drug spending is capped at $2,100, and no Part D plan may charge a deductible above $615. Once you hit the cap, covered drugs cost you nothing for the rest of the year.
So the full Original Medicare stack is: Part B premium, Medigap premium, Part D premium, and very little else. You pay more every month and almost nothing when you get sick.
How Medicare Advantage works: Part C bundling
A Medicare Advantage plan is sold by a private insurer that contracts with Medicare. You stay in the Medicare program, but the insurer, not the government, administers your benefits, builds your provider network, sets your copays, and decides what gets approved.
Most plans fold in drug coverage. In 2026, 89% of individual Medicare Advantage plans include prescription drug coverage, and 67% of those charge no premium beyond the standard $202.90 Part B premium. The zero-premium marketing is accurate as far as it goes. You still owe Part B every month. What you skip is the Medigap premium and the separate drug plan premium.
Instead of paying 20% of everything, you pay flat copays: a set amount for a primary care visit, more for a specialist, a daily rate for hospital days, a percentage for some expensive treatments. Those copays run until you hit the plan’s annual out-of-pocket maximum, after which the plan covers Medicare-approved services in full for the rest of the year.
Plans come in two main shapes. HMOs are cheaper and generally cover nothing outside the network except emergencies, and they often require a referral before you see a specialist. PPOs cost more and pay something toward out-of-network care, usually at a higher copay. HMOs made up 57% of plans offered in 2026, with local PPOs at 42%.
Networks change. Plans change. About 2.6 million people were in a Medicare Advantage plan that stopped operating at the end of 2025. Reading the Annual Notice of Change your plan mails every September is genuinely worth an hour of your time, because that is where premium, copay, drug list, and network changes get disclosed.
Side-by-side comparison
| Original Medicare (with Medigap and Part D) | Medicare Advantage | |
|---|---|---|
| Providers | Any doctor or hospital in the US that accepts Medicare, which is most of them | Plan network only for HMOs; PPOs pay less for out-of-network care |
| Referrals | Not required | Often required by HMOs to see a specialist |
| Monthly cost | Part B ($202.90) plus Medigap plus Part D, so typically the higher monthly bill | Part B plus often $0 in plan premium |
| Cost when sick | Very low and predictable with Plan G, usually just the $283 Part B deductible | Copays until you hit the plan’s out-of-pocket maximum |
| Annual spending cap | None from Medicare itself; Medigap is what limits your exposure | Required. In 2026 the cap cannot exceed $9,250 in network or $13,900 combined, and the average enrollee’s in-network cap is $5,421 |
| Travel | Works anywhere in the US; some Medigap plans add limited foreign emergency coverage | Emergencies covered anywhere, routine care usually only in your service area |
| Dental, vision, hearing | Not covered, buy separately | Commonly included, with annual dollar limits |
| Prior authorization | Rare | Routine. In 2026, 95% of enrollees are in a plan requiring prior authorization for skilled nursing stays |
Where Original Medicare wins
The network advantage is real and it is the reason many people with serious conditions stay put. If you get a diagnosis that sends you to a specialist three states away, Original Medicare goes with you. No referral, no out-of-network tier, no argument about whether that hospital is in your plan’s service area. Snowbirds, people who spend months near grandchildren, and anyone likely to need a major academic medical center get a lot of value from this.
Prior authorization is the second one, and the numbers are not close. Medicare Advantage insurers made nearly 53 million prior authorization determinations in 2024, and denied 4.1 million of them, or 7.7%. Traditional Medicare processed just over 625,000 requests that year, which works out to 0.02 per beneficiary, against 1.7 per Medicare Advantage enrollee. Insurers now have to publish their own numbers, and the first round was worse than the older data suggested: Medicare Advantage plans denied 12% of standard prior authorization requests in 2025. Denials get overturned on appeal at a high rate, which sounds reassuring until you notice that most patients never file an appeal. All of this comes from KFF, a nonprofit health policy group with no plan sales in the mix, which is more than you can say for most sources quoting these figures.
Third is cost predictability. With Plan G, your worst medical year and your best medical year cost about the same. You pay a known premium every month and the $283 Part B deductible once, and the rest is covered. For people on a fixed income, a bill you can forecast is often worth more than a lower average bill.
Where Medicare Advantage wins
Cash flow is the obvious one. Nearly all beneficiaries (98%) have access to a drug-inclusive plan with no premium beyond Part B in 2026. If your budget cannot absorb a Medigap premium every month, that is not a rounding error, it is the deciding factor. A plan that you can afford beats a plan you drop in March.
The out-of-pocket maximum is the part people underrate. Original Medicare on its own has no cap at all, so the Medigap premium is really the price of buying one. Medicare Advantage builds the cap in for free, and most plans set theirs well below the legal ceiling. The average in-network cap in 2026 is $5,421, with HMOs averaging $4,636 and PPOs $6,592. That said, roughly 9% of enrollees, about 1.8 million people, are in a plan sitting right at the $9,250 maximum, so check the actual number in your plan documents rather than assuming.
Extras are the third draw, and they are genuinely useful for routine needs. Most plans include dental, vision, and hearing benefits, sometimes with a fitness membership or an over-the-counter card. Read the limits before you count on them. A dental benefit is usually a fixed annual allowance, often a few thousand dollars at most, which covers cleanings and fillings comfortably and stops well short of implants or a full set of crowns. Plan brochures tend to describe these benefits more generously than the coverage documents do.
The switching problem nobody mentions
Moving from Original Medicare to Medicare Advantage is easy. You do it during open enrollment, October 15 to December 7, and nobody asks about your health.
Moving back is not symmetrical. You can drop a Medicare Advantage plan and return to Original Medicare, and Medicare will take you. The catch is Medigap, and without Medigap, Original Medicare leaves you exposed to unlimited 20% coinsurance. Federal law gives you one guaranteed window to buy a Medigap policy: the six months starting when you are 65 and enrolled in Part B. During those six months, insurers must sell to you at standard rates no matter what your chart says. After it closes, in most states they can ask health questions, charge you more, or turn you down.
That means the decision you make at 65 is not fully reversible at 75. If you spend a decade in Medicare Advantage, develop diabetes and a heart condition, and then decide you want to go back to any doctor without prior authorization, the Medigap insurer can decline you. You would return to Original Medicare with no cap on your spending, which is the worst of both options.
There are exceptions worth knowing:
- A trial right. If you joined Medicare Advantage when you first became eligible at 65, you can leave within the first 12 months and buy a Medigap policy with guaranteed issue. Same protection applies if you dropped a Medigap policy to try Medicare Advantage for the first time and change your mind inside a year.
- If your plan leaves your area or stops covering your county, you get guaranteed issue rights.
- State rules. About 16 states have a “birthday rule” in 2026, giving existing Medigap holders a short annual window to switch policies without health questions, with Delaware and Indiana joining on January 1, 2026 and West Virginia on June 11, 2026. Connecticut, New York, and Vermont go further and allow year-round guaranteed issue. Note that these mostly let you switch between Medigap plans, not enter Medigap for the first time after years in Medicare Advantage.
Two things to be clear about. The October 15 to December 7 annual enrollment period applies to Medicare Advantage and Part D. It does not give you a right to buy Medigap without underwriting. And this asymmetry is not a reason to avoid Medicare Advantage. It is a reason to treat the choice at 65 as more consequential than the marketing suggests, and to check your own state’s rules before you assume you can undo it.
Questions to ask yourself before choosing
Can you comfortably pay a Medigap premium every month for the rest of your life, including years when you barely see a doctor? Do your current doctors take the plan you are considering, and would you switch doctors if the network changed next year? Do you spend significant time away from home? Do you have a condition that makes future medical underwriting likely to go badly for you? Would you rather pay more in a healthy year for certainty, or less now and accept copays when things go wrong?
Nobody can answer those for you, and anyone who gives you a confident recommendation before asking them is selling something. Your State Health Insurance Assistance Program (SHIP) offers free counseling from people who earn no commission, which is a reasonable place to check your reasoning before you commit.
