The 5 Medicare Enrollment Mistakes That Cost People the Most Money
Medicare enrollment seems like it should be straightforward. You turn 65, you sign up, you're covered. But the details matter — and getting them wrong can cost you for years.
Here are the five most common mistakes, what they actually cost, and how to avoid them.
Mistake #1: Missing Your Initial Enrollment Period
When you turn 65, you have a 7-month Initial Enrollment Period to sign up for Medicare. It starts three months before the month of your 65th birthday and ends three months after.
If you miss this window — and don't have a valid reason for it, like being covered by a current employer's group health plan — you'll pay a permanent late enrollment penalty on your Part B premium. That's a 10% increase for every 12-month period you were eligible but didn't sign up. And it doesn't go away. You carry it for life.
Miss it by two years and your Part B premium goes up 20% permanently. That adds up to thousands of extra dollars over a 20-year retirement.
How to avoid it: Know your window and mark it on your calendar well in advance of your 65th birthday.
Mistake #2: Enrolling Without Checking If Your Doctors Are In-Network
This one is especially common with Medicare Advantage plans. Someone picks a plan because the premium looks great, then shows up to their doctor's appointment and finds out their doctor doesn't participate in that plan.
At best, that means paying higher out-of-network rates. At worst, it means finding a new doctor — which can be especially disruptive if you have ongoing health conditions and an established relationship with a specialist.
How to avoid it: Before you enroll in any Medicare Advantage plan, look up your primary care doctor, every specialist you see regularly, and your preferred hospital. Confirm all of them are in the plan's network.
Mistake #3: Ignoring the Drug Formulary
A formulary is the list of prescription drugs a plan covers — and what tier each drug falls on. Higher tiers mean higher copays.
Plans change their formularies every year. A drug that was a $10 copay last year might now be $65. A drug that was on the formulary at all might now require prior authorization or be dropped entirely.
This one catches people off guard constantly. They assume their medications are covered the same as before, and they're not.
How to avoid it: Every year during Open Enrollment, run your current medications through each plan's drug search tool — or have an agent do it for you — to confirm your costs before you commit.
Mistake #4: Assuming All Medicare Advantage Plans Are the Same
Medicare Advantage plans can look similar on the surface — lots of them have $0 premiums and include dental and vision. But the differences in out-of-pocket maximums, specialist copays, network size, and drug formularies can be enormous.
Two $0-premium plans in the same zip code can have wildly different real-world costs depending on how often you use healthcare and which conditions you have.
How to avoid it: Look past the premium. Compare the maximum out-of-pocket limit, your specific doctors and drugs, and how specialist visits are handled. A plan that costs more upfront sometimes costs far less overall.
Mistake #5: Never Reviewing the Plan After You Enroll
This may be the most common mistake of all. Once people sign up, they rarely look at it again.
But plans change every year. Networks change. Drug tiers change. Premiums creep up. What worked at 65 may not work at 70 — both because the plan has changed and because your health may have changed.
The Open Enrollment window every fall exists specifically so you can make adjustments. Most people let it pass without looking at anything.
How to avoid it: Every fall, take an hour to review your plan. Better yet, work with an independent agent who does this as part of their ongoing relationship with you — not just when you first enroll.
Key Takeaways
Missing your Initial Enrollment Period creates a permanent premium penalty that lasts your entire retirement
Always verify your doctors and medications are covered before enrolling in any plan
Plans change every year — reviewing your coverage annually is one of the most valuable things you can do
Mistakes like these are more common than most people know — and most of them are entirely avoidable. If you want a second set of eyes on your coverage, or if you're approaching enrollment for the first time, we're happy to walk through it with you.
