This is the fork in the road. Every other Medicare decision can be revisited at some later enrollment period. This one can become permanent, because leaving Medicare Advantage is easy and buying a Medigap policy afterwards may not be.
So it is worth getting right the first time.
What each one actually is
Medicare Advantage (Part C) is a private plan that takes over delivery of your Part A and Part B benefits. Medicare pays the carrier a fixed monthly amount per member, and the carrier manages your care within that budget — which is why there are networks, referrals, prior authorisations and tiered formularies, and also why there is room for extras like dental allowances and gym memberships.
Medicare Supplement (Medigap) is a private policy that sits alongside Original Medicare. Medicare pays your claims as usual; the supplement pays the deductibles and coinsurance Medicare leaves behind. There is no network because Original Medicare has no network. Drug coverage is not included, so you buy a standalone Part D plan.
You can hold one or the other. Never both.
Side by side
| How it works | Medicare Advantage | Medigap + Part D |
|---|---|---|
| Monthly premium | Part B, plus often $0 plan premium | Part B, plus Medigap premium, plus Part D premium |
| Provider access | The plan’s network | Any provider nationwide accepting Medicare |
| Referrals | Often required (HMO) | Never required |
| Prior authorisation | Common | Rare |
| Out-of-state care | Emergency/urgent only on most HMOs | Full coverage nationwide |
| Drug coverage | Usually included | Separate Part D plan |
| Dental, vision, hearing | Frequently included | Not included; buy separately |
| Cost at the doctor | A copay each visit | Usually nothing after the Part B deductible |
| Annual worst case | The plan’s out-of-pocket maximum | Essentially the Part B deductible |
| Changes each January | Network, formulary, copays, extras | Nothing — the benefit chart is federally standardised |
| Premium over time | Re-set annually, often stable | Rises with age, inflation and claims experience |
| Can you be turned down later? | No — Advantage is guaranteed issue | Yes, outside your open enrollment window |
The five questions that settle it
After several hundred of these conversations, the answer almost always falls out of five questions.
1. Are your doctors in the plan’s network — and how attached are you to them?
This is the first filter and it eliminates candidates faster than anything else. Name your primary care physician, every specialist you see, and the hospital you would want to use. If a plan’s network does not include them, it is not a candidate, no matter how good the extras look.
If your specialists are at a teaching hospital and you would not consider changing, that fact alone often points toward Medigap — which has no network at all.
2. Do you travel, or spend part of the year elsewhere?
Most Advantage HMOs cover only emergency and urgent care outside the service area. If you spend winters in another state, see doctors in two places, or travel for months at a time, Medigap travels considerably better. A PPO is the middle ground.
3. Can you comfortably carry the Medigap premium — for the next twenty-five years?
Medigap premiums are real money every month, and they rise. The question is not whether you can afford it this year but whether you can afford it at 82, after two decades of increases, on a fixed income.
If the honest answer is no, a Medicare Advantage plan with a manageable out-of-pocket maximum is a better plan than a Medigap policy you eventually have to drop — because dropping it at 82 leaves you with no route back.
4. What does a bad year look like on each?
Compare the worst case, not the average. On Medigap, a catastrophic year costs you roughly the Part B deductible. On a Medicare Advantage plan it costs you up to the out-of-pocket maximum, which varies enormously between plans in the same county.
Look at that number. Ask yourself whether you could write that check in a year you were also seriously unwell.
5. Would prior authorisation bother you?
This is a temperament question and it is a legitimate one. Advantage plans manage utilization, which sometimes means a delay while an authorisation is processed, or a denial that has to be appealed. Some people find that an acceptable trade for a lower premium and bundled extras. Others find it intolerable. Both positions are reasonable — but know which one you hold before you choose.
The asymmetry that makes this decision different
Joining a Medicare Advantage plan is always possible — Advantage plans are guaranteed issue for anyone with Parts A and B in the service area.
Buying a Medigap policy is only guaranteed during your six-month Medigap Open Enrollment Period starting when Part B begins, or in specific guaranteed-issue situations. Outside those, most states let the carrier underwrite your health and decline.
So the door swings freely in one direction and can lock in the other. That is why the choice at 65 deserves more thought than any later one.
The Medigap trial right
There is one genuine safety net. If you join a Medicare Advantage plan for the first time at 65 and decide within twelve months that you would rather be on Original Medicare, you generally have a guaranteed-issue right to buy a Medigap policy without underwriting.
It is a real protection and it is worth knowing about if you are leaning toward Advantage but uncertain. It also has a hard edge: twelve months, once, and only if this is your first Advantage plan.
Where each one genuinely wins
Medigap is usually right when:
- You want to see any provider in the country without a network or a referral
- You travel, snowbird, or split the year between states
- You have a chronic condition producing frequent claims
- You would rather pay a known premium than variable copays
- The premium is comfortable now and would still be comfortable in twenty years
- You are inside your six-month open enrollment window
Medicare Advantage is usually right when:
- Your doctors and hospital are in a strong local network
- You stay mostly in one area
- The premium difference is meaningful to your monthly budget
- You want dental, vision, hearing or an OTC allowance bundled in
- You are comfortable with copays and occasional prior authorisation
- The plan’s out-of-pocket maximum is a number you could handle in a bad year
What we actually do
We do not have a house view. We run the five questions, check every doctor against every candidate network, run your prescriptions against every formulary, and put the realistic options side by side with a best-year and worst-year cost for each.
Then we tell you which one we would put a family member on, and why — and you decide.
Next steps
Work out your dates with the enrollment window checker, read the detail on Medicare Advantage and Medicare Supplement, then book a free comparison.
There is no fee, and a meaningful share of these conversations end with us telling someone to stay exactly where they are.
Frequently asked questions
Which is better, Medicare Advantage or Medigap?
Neither is better in the abstract, and anyone who tells you otherwise is selling something. Medigap suits people who value unrestricted provider access and predictable costs and can carry the monthly premium. Medicare Advantage suits people whose doctors are in-network, who stay mostly local, and who prefer a low fixed premium with usage-based costs capped by an out-of-pocket maximum.
Can I switch from Medicare Advantage to Medigap later?
You can leave an Advantage plan during the Annual Enrollment Period or the Medicare Advantage Open Enrollment Period. Getting a Medigap policy afterwards is the harder half — outside your six-month Medigap open enrollment window or a guaranteed-issue right, most states allow the carrier to underwrite your health and decline you.
Is a $0 premium Advantage plan too good to be true?
No, the $0 is real — Medicare pays the carrier a monthly amount to manage your care, and a carrier that delivers benefits for less can offer a $0 plan premium. What the $0 does not mean is $0 cost. You still pay your Part B premium, and you pay copays as you use care up to the plan’s out-of-pocket maximum.
What is the Medigap trial right?
If you join a Medicare Advantage plan for the first time at 65 and decide within twelve months that you would rather have Original Medicare, you generally have a guaranteed-issue right to buy a Medigap policy without underwriting. It is a genuine safety net, and it only lasts twelve months.