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 authorisation applies to more services than people expect.
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.
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 neighbour may be the wrong one for you.
One thing worth planning around: the Medigap Open Enrollment window — six months from when you're 65 and on Part B — is the one time you can buy a Supplement with no health questions. If you're leaning that way at all, timing matters.