If you are turning 65 or reviewing your coverage right now, you have probably stared at two stacks of mail: Medicare Advantage plans promising $0 premiums and extra perks, and Medigap supplements with monthly bills that look like a car payment.
The difference between these two paths can swing your yearly health costs by thousands of dollars, and the wrong pick is hard to undo.
Original Medicare (Part A hospital, Part B doctor visits) covers about 80% of most costs.
Medicare Advantage, also called Part C, replaces that setup with a private plan, often an HMO or PPO, that usually includes drug coverage and may add dental, vision, and gym benefits.
You typically pay the Part B premium plus copays as you use care.
A Medicare Supplement, or Medigap, works differently.
You keep Original Medicare and buy a private policy that picks up most of the leftover 20%, plus hospital deductibles depending on the letter plan you choose.
You pay a monthly premium whether you see a doctor or not, and you generally need a separate Part D drug plan.
The trade-off is predictable: Advantage tends to win on low fixed costs, while Medigap tends to win when you actually get sick.
A 2024 KFF analysis found that typical out-of-pocket spending for people with traditional Medicare plus a supplement was lower than for Advantage enrollees, even though their premiums were higher.
Advantage plans also cap yearly out-of-pocket costs, but those caps can run $8,000 or more for in-network care.
The fine print matters more than the brochure.
Advantage networks can require referrals and prior authorization, and a 2023 federal review found some denials that should have been approved.
Medigap, by contrast, lets you see any provider nationwide who accepts Medicare, with no referrals.
If you travel a lot or have a serious diagnosis, that flexibility is worth real money.
Medigap insurers in most states can reject you or charge more based on health history after your initial enrollment window, which runs six months from when you first sign up for Part B.
Switch from Advantage to Medigap later, and you may face medical underwriting.
A handful of states, including New York and Connecticut, have looser rules, but most do not.
So run your own numbers before December 7.
Add up premiums, deductibles, and the copays you would face in a bad year, not just a good one.
Check whether your doctors and hospitals are in each Advantage network.
If you take expensive drugs, price them under each plan's formulary, because a $0 premium means little if your prescription costs $400 a month.
My take: if you can comfortably afford the premium and want fewer financial surprises, Medigap is usually the safer long-term bet, especially because you can switch into it easily at 65 but not always later.
If cash flow is tight and you are generally healthy, a well-reviewed Advantage plan can work, as long as you read the network rules first.
Final Thoughts
Either way, treat this like a household budget decision, not a marketing one, because the paperwork you ignore now shows up as a bill later.