If you're turning 65 this year, you're about to face a decision that quietly shapes your health care budget for the rest of your life.
Pick a Medicare Advantage plan and you might pay $0 in monthly premiums.
Pick a Medigap supplement and you'll likely pay $150 to $250 a month on top of your Part B premium.
That gap looks obvious until you dig into what each path actually covers when you get sick.
Medicare Advantage, known as Part C, is run by private insurers like UnitedHealthcare, Humana, and Aetna.
The pitch is simple: the government pays these companies a set amount per member, and in exchange you get hospital, medical, and usually drug coverage bundled into one card.
Many plans throw in dental, vision, hearing aids, and a gym membership.
Some even send you a debit card for groceries or over-the-counter items.
In 2024, more than half of all eligible Medicare beneficiaries chose this route, according to KFF, and the average premium sits near $18 a month.
See an out-of-network specialist and you may pay the full bill.
They also require prior authorization for many procedures, and a 2023 federal report found some insurers denied requests that should have been covered.
Out-of-pocket costs are capped, but that cap can run $8,850 in-network for 2024, and higher if you go out of network.
Original Medicare plus a Medigap supplement works differently.
You pay your Part B premium, roughly $174.70 a month in 2024, plus a supplement premium.
In return, Medigap picks up most or all of what Medicare doesn't cover.
You can see any doctor in the country who accepts Medicare, which is the vast majority.
No referrals, no prior authorization for most care.
The trade-off is cost certainty versus cost flexibility.
Medigap Plan G, the most popular new-enrollment choice, covers nearly everything except the Part B deductible, which was $240 in 2024.
After that, a serious illness like cancer or a heart attack could cost you almost nothing beyond premiums.
The same event under an Advantage plan could trigger copays for every hospital day, specialist visit, and scan until you hit that annual cap.
In most states, you only get a guaranteed right to buy a Medigap policy during your six-month Medigap Open Enrollment Period, which starts when you're 65 and enrolled in Part B.
Wait until you're 70 and have a diagnosis of diabetes or heart disease, and an insurer can reject you or charge far more.
Advantage plans, by contrast, must accept you during annual enrollment regardless of health.
That asymmetry pushes many advisors to suggest starting with Medigap if you can afford it, since switching later can be nearly impossible.
Medigap does not, so you'll buy a standalone Part D plan, often for $15 to $50 a month.
The Inflation Reduction Act capped insulin at $35 a month and out-of-pocket drug costs at $2,000 a year starting in 2025, which softens the blow on both paths.
If you have chronic conditions, travel often, or want to see specialists without permission slips, Medigap's higher premium often buys peace of mind.
If you're healthy, live on a tight budget, and don't mind staying in-network, Advantage can keep monthly costs near zero, as long as you can absorb a surprise bill.
The honest answer is that this isn't a one-size decision.
It's a math problem built on your health, your doctors, your state, and your savings.
Run the numbers before you enroll, because the choice you make at 65 can follow you for decades.
Our take: treat the low premium on an Advantage plan as a starting price, not the final one, and treat Medigap's monthly cost as insurance against the bill you can't predict.
Final Thoughts
Whichever way you lean, decide with your actual doctors and prescriptions in front of you, not a brochure.