If you are turning 65 or reviewing your coverage right now, you have probably stared at two very different options: Medicare Advantage (Part C) and Medicare Supplement (Medigap).
They behave nothing alike when a bill shows up.
Original Medicare (Parts A and B) pays most, but not all, of your care.
Advantage plans replace Original Medicare with a private insurance package, usually bundling drug coverage and extras like dental or vision.
Medigap works alongside Original Medicare and mainly covers your share of the cost.
The trade-off comes down to premiums versus predictability.
Medicare Advantage often advertises a $0 monthly premium, which is why it now covers more than half of eligible enrollees, according to federal data.
But that low premium is not the whole story.
Advantage plans use networks, prior authorizations, and copays that can add up fast if you need specialists, imaging, or a hospital stay.
You pay a monthly premium on top of your Part B premium, and it can run well over $100 a month depending on your age, state, and plan letter.
In return, many plans cover nearly all of your out-of-pocket costs after you meet the Part B deductible.
A recent KFF analysis found that a meaningful share of Advantage enrollees who need a lot of care can face thousands in cost sharing.
Meanwhile, Medigap enrollees tend to have more stable yearly costs, but they pay for that stability every month whether they use it or not.
The decision usually hinges on three things: your health, your budget, and your tolerance for paperwork.
If you are generally healthy, take few prescriptions, and want the lowest possible monthly cost, an Advantage plan can work well.
If you have ongoing conditions, see multiple doctors, or travel a lot, Medigap plus a standalone Part D drug plan often brings fewer headaches.
One trap catches people every year: switching later.
In most states, Medigap insurers can ask about your health once you are past your initial enrollment window.
That means a plan you can easily buy at 65 may be denied or priced higher at 72.
Advantage plans, by contrast, must accept you during certain enrollment periods.
So the "cheaper" choice now can quietly become the expensive one later if your health changes.
List every doctor and drug you use, then check each plan's network and formulary.
Add up the worst-case yearly cost, not just the premium.
And call your state's Senior Health Insurance Program for free, unbiased help.
A few quick numbers to ask about: the annual out-of-pocket maximum, whether prior authorization is required for common services, and what a three-day hospital stay would actually cost you. **The bottom line:** Advantage plans win on the sticker price, and Medigap wins on predictability.
The mistake is choosing based on the monthly premium alone and discovering the real cost the first time you get sick.
Final Thoughts
Run the full-year math, and pick the plan that fits your health, not just your mailbox.