If you're turning 65 or reviewing your coverage right now, you're staring down one of the most expensive decisions in retirement.
It comes down to two paths: Medicare Advantage or a Medigap supplement.
Pick wrong, and you could be on the hook for thousands in medical bills you never saw coming.
Medicare Advantage (Part C) is an all-in-one plan from a private insurer that replaces Original Medicare, often bundling in drug coverage and extras like dental or vision.
Medigap, also called a Medicare Supplement, doesn't replace anything—it sits alongside Original Medicare and covers the gaps, like the 20% of costs Medicare doesn't pay.
Advantage plans usually have low or $0 monthly premiums, which is why they're popular.
But those low premiums hide copays, deductibles, and annual out-of-pocket maximums that can run past $8,000 in 2024.
You'll pay a higher monthly premium—often $100 to $200 or more depending on your state and plan letter.
In exchange, most plans pick up nearly all of that 20% coinsurance, so a hospital stay or cancer treatment won't wreck your budget.
Many people on Medigap Plan G see predictable costs: the premium, plus the Part B deductible.
Then there's the rule that trips people up.
With Medigap, you generally get your best shot to enroll during your six-month Medigap Open Enrollment Period, which starts the month you're 65 and enrolled in Part B.
Miss it, and in most states insurers can charge you more or deny you outright based on your health history.
Advantage plans don't work that way—you can often switch during annual enrollment, but you may not be able to buy a supplement later if your health changes.
Advantage plans usually use HMOs or PPOs, so you're often locked into a provider network and may need referrals.
Original Medicare with a supplement lets you see almost any doctor nationwide who accepts Medicare.
If you travel a lot or have a specialist you trust, that flexibility is worth real money.
One more catch: Advantage plans can change their provider networks, drug formularies, and copays every single year.
Your $0 premium plan might look very different in 12 months.
Supplements are more stable, though your premium can still rise with age or inflation.
If you're healthy, rarely see doctors, and want the lowest possible monthly bill, an Advantage plan can work—just keep an emergency fund ready for the bad year.
If you have ongoing conditions, take expensive drugs, or simply want to know your costs ahead of time, a supplement often pays for itself in peace of mind.
The honest take: this isn't about which plan is "better." It's about which risk you can live with.
Low monthly costs with unpredictable bills, or higher premiums with fewer surprises.
Final Thoughts
Run your own numbers against your actual prescriptions and doctors before you decide, because a sales pitch won't pay your hospital bill.