Jesse Smedley is a Principal of Oakbridge Insurance and the founder of iHealthBrokers. He founded iHealthBrokers in 2007, and Oakbridge acquired iHealthBrokers in 2025. He has spent nearly two decades teaching people how to save money on their health insurance and navigate Medicare, and he is the author of Medicare A to Z: Your Roadmap to Medicare.
Most Medicare mistakes don’t feel risky when you make them. Keeping COBRA for a few extra months seems sensible. Picking the plan with the lowest premium seems like a smart way to save.
The problem is you may not see the cost until later: a penalty shows up, your doctor is out of network, or a better plan is no longer available to you. Here are 8 common Medicare mistakes and how to avoid each one.
1. Paying for Medicare and Employer Coverage You Don’t Need
Most people become eligible for Medicare at 65. If you already get Social Security or Railroad Retirement benefits, you’ll be enrolled automatically and your Medicare card will arrive in the mail.
Your Initial Enrollment Period is the 7 months around your 65th birthday: the 3 months before, your birthday month and the 3 months after. If you aren’t enrolled automatically, you can sign up through Social Security during this window.
If you’re still working and have coverage through a current employer, you may be able to delay Medicare, especially Part B. Many people are enrolled automatically, don’t realize they can delay Part B, and end up paying two premiums: one to Medicare and one to their employer plan.
A few months before you turn 65, compare the costs and benefits of Original Medicare with your employer plan. Keep in mind that Medicare covers individuals only. Your spouse and dependents aren’t covered by your Medicare, so plan for their coverage too. If you’re working past 65, read Working Past 65: Should You Enroll in Medicare or Wait?
2. Relying on COBRA Instead of Medicare
COBRA lets you keep your employer’s health plan for a while after you leave the job. It’s a useful bridge, but Medicare doesn’t treat it as coverage based on current employment. If you’re eligible for Medicare and keep COBRA instead of enrolling in Part B, you could owe a late enrollment penalty later.
Your Special Enrollment Period to sign up for Part B lasts 8 months and starts the month after your job or your employer coverage ends, whichever comes first. Having COBRA doesn’t extend it. When COBRA ends, a new enrollment window doesn’t start.
It gets trickier when a spouse is involved. If you move to Medicare and your spouse is on your employer plan, your spouse can often keep that coverage through COBRA. Depending on timing, your spouse may be able to keep it for up to 36 months, which can bridge the gap until they’re eligible for Medicare. Check the exact dates with your employer’s benefits team.
3. Forgetting About HSA Contributions
If you have a high-deductible health plan, you may be contributing to a health savings account (HSA) to lower your taxable income. That’s a great tool, but once you enroll in Medicare, you can no longer contribute.
There’s a catch. If you enroll in Part A after 65, your Part A coverage can be backdated up to 6 months. Any HSA contributions you made during those months may no longer be tax-free.
This doesn’t apply if you enroll at 65, because Part A isn’t backdated to before your 65th birthday. But if you’ve delayed Medicare and kept contributing, it matters. For example, if you enroll at 67 and contributed to your HSA three months ago, those contributions could create a tax problem.
The fix is simple: stop HSA contributions at least 6 months before you plan to enroll in Medicare.
4. Skipping Part D Because You Don’t Take Prescriptions
Original Medicare doesn’t cover most prescription drugs. You need a separate Part D plan, or a Medicare Advantage plan that includes drug coverage.
Many people who are healthy when they first enroll decide they don’t need Part D. That’s understandable, but if you go 63 days or more in a row without Part D or other creditable drug coverage after your Initial Enrollment Period ends, you may owe a late enrollment penalty for as long as you have drug coverage.
The Part D penalty is usually much smaller than the Part B penalty, sometimes just a few dollars a month. But it’s easy to avoid, and some areas have Part D plans with no monthly premium. A low-cost plan also protects you if you suddenly need a medication next month.
5. Choosing a Medicare Advantage Plan by Premium Alone
Medicare Advantage plans vary widely in cost and benefits, and many have a $0 monthly premium. You still pay your Part B premium, and the premium shouldn’t be the deciding factor.
Compare copays, coinsurance, deductibles and the out-of-pocket maximum. Then check these:
- Networks. Medicare Advantage plans use networks, and some are narrow. Make sure your doctors and hospitals are in network, or that $0 premium won’t help when you get the bill.
- Drug list. Most Medicare Advantage plans include drug coverage. Make sure your prescriptions are on the plan’s formulary.
- Prior authorization. Find out which services need approval first and which have limits.
6. Missing Your Medigap Window
The other route is Original Medicare with a Medicare Supplement (Medigap) plan. You keep the freedom of Original Medicare and reduce or eliminate most out-of-pocket costs. We consider it the gold standard, especially Plan G. See how every plan stacks up in Best and Worst Medigap Plans for 2026, Ranked.
Unlike Medicare Advantage and Part D, Medigap doesn’t have an annual enrollment period. Your best chance to buy one is your Medigap Open Enrollment Period: the 6 months that start once you’re 65 and enrolled in Part B. During that window, companies can’t deny you or charge you more because of your health. Outside of it, you may have to answer health questions, and you could be charged more or turned down.
Many people start with Medicare Advantage because of the low premiums and extra benefits. Later, when their health changes, they want to switch to a Medigap plan, and in most states that means medical underwriting.
One more tip: if you’re past 65, still working and want to delay Part B, follow the instructions that come with your Medicare card to decline it. If you keep the card, you’ll pay for Part B and your Medigap window will start, too.
7. Ignoring Your Annual Notice of Change
Medicare plans change every year. If you have a Medicare Advantage or Part D plan, you’ll get an Annual Notice of Change each fall. Don’t toss it with the junk mail.
It tells you whether your plan will still be offered next year and what’s changing with doctors, hospitals, networks, covered drugs, premiums, copays, coinsurance, deductibles and the out-of-pocket maximum. You may find your plan no longer fits and there’s a better option.
8. Falling for a Medicare Scam
Medicare scams are on the rise. Scammers target people who are vulnerable, and if it happens to you, it’s not your fault. Knowing the signs is the first step.
Medicare won’t call you out of the blue asking for personal information. If you didn’t request a call and someone asks for your Social Security number or Medicare number, hang up and report it by calling 1-800-MEDICARE.
Take 10 Minutes Today
Find the next Medicare deadline that applies to you, whether it’s the end of your employer coverage, your Initial Enrollment Period or the Annual Enrollment Period, and put it on your calendar. You can confirm dates on Medicare.gov or in our Medicare enrollment guide.
If you’re working past 65, take a closer look at how turning 65, Medicare enrollment and HSA contributions fit together, because they don’t run on the same clock. Want a second set of eyes? Get your free quotes or call a licensed broker at (866) 260-9829.
