This is the biggest decision most people make at 65, and it's frequently presented badly — usually by someone with a reason to prefer one answer.
Medicare Supplement (Medigap)
You keep Original Medicare and add a policy that fills its gaps. You then add a separate Part D drug plan.
- Any doctor who accepts Medicare — no networks, no referrals, and it works anywhere in the country.
- Predictable costs — you pay a monthly premium and, depending on the plan, very little else when you use care.
- Higher premium — you're paying up front for that certainty.
- Health questions apply outside your Medigap Open Enrollment window.
Medicare Advantage (Part C)
A private plan that replaces Original Medicare and usually bundles in drug coverage.
- Low or $0 monthly premium, which is genuinely attractive on a fixed income.
- Extra benefits Original Medicare doesn't cover — often dental, vision and hearing.
- Networks and referrals — you're generally choosing from a defined list of providers.
- Costs when you use it — copays and an annual out-of-pocket maximum, so a heavy year costs more than a light one.
- Prior authorization applies to more services than people expect.
The two paths, side by side.
What changes depending on which way you go at 65.
| Supplement | Advantage | |
|---|---|---|
| Doctors | Any doctor who accepts Medicare | A network, often with referrals |
| Travel | Works anywhere in the U.S. | Mostly local outside emergencies |
| Monthly premium | Higher | Low, often $0 |
| Costs when you use care | Little or nothing more | Copays up to a yearly maximum |
| Dental, vision, hearing | Add a separate plan | Often some included |
| Prior authorization | Rarely | More often than people expect |
| Switching later | Health questions outside your window | Possible, but the Supplement may then underwrite you |
How I'd actually think about it
Ask yourself three questions:
- Do you have doctors you refuse to give up? Check the network before anything else.
- Do you travel, snowbird, or spend months elsewhere? Networks become a real problem when you're away.
- Would an unpredictable medical year be a genuine hardship? If so, the Supplement's predictability may be worth its premium.
Where I tend to land
Before that, one thing to know about the order you do this in: if you want a Supplement, the easiest time to get one is during your six-month Medigap Open Enrollment window, when no health questions are asked. Starting on an Advantage plan and switching to a Supplement later is possible, but you may have to answer for your health to do it. The sequence matters. One safety net worth knowing: if you join an Advantage plan when you first become eligible at 65, federal rules give you twelve months to change your mind, return to Original Medicare and buy a Supplement without health questions.
I help with both, and when an Advantage plan genuinely fits someone's situation, I'll say so. That said, many of my clients end up on a Supplement — for the any-doctor freedom and the predictable costs. It's coverage you don't have to think about, and at 65 that's worth something.
What I won't do is default you into a plan because it's the easier sale. The right answer for your neighbor may be the wrong one for you.