We Asked 5 Experts About the No. 1 Mistake People Make With Medicare—Here's What They Had to Say

Key Takeaways

Don’t rush your Medicare decision. Many retirees skip comparing Original Medicare vs. Medicare Advantage, risking limited doctor access and fewer coverage options.
Medigap isn’t guaranteed later. If you enroll in Medicare Advantage first, switching to Original Medicare with Medigap later may be denied due to health conditions—unless it’s during your initial six-month Medigap enrollment window.
Watch your income two years before Medicare. Premiums for Part B and Part D are based on your Modified Adjusted Gross Income (MAGI) from two years prior. Moves like Roth conversions, IRA withdrawals, or selling assets can trigger IRMAA surcharges, raising your monthly costs by hundreds.

Top Medicare Mistakes: What Financial Planners and Legal Experts Say to Avoid

Medicare enrollment can feel overwhelming especially when you're juggling income-related premium adjustments and trying to choose the right Medigap plan. To simplify the process, five experts including certified financial planners and a Medicare-focused attorney shared the most common mistakes retirees make:

Skipping the Medicare Advantage vs. Original Medicare comparison: Many retirees default to one without understanding how it affects doctor access, referrals, and out-of-pocket costs.
Missing the Medigap enrollment window: After your initial six-month Medigap eligibility period, insurers can deny coverage based on health status.
Ignoring income-based premium surcharges: Medicare Part B and D premiums are based on your Modified Adjusted Gross Income (MAGI) from two years prior. Strategic moves like Roth conversions or asset sales can trigger IRMAA surcharges.
Assuming automatic coverage includes everything: Automatic enrollment doesn’t include Part D drug coverage or Medicare Advantage—you must opt in.
Trusting unsolicited calls or mailers: Scammers often target new enrollees with fake plan offers. Always verify through Medicare.gov or call 1-800-MEDICARE.

One of the biggest Medicare mistakes? Not doing enough research before enrolling. In 2025, over 54% of eligible beneficiaries chose Medicare Advantage, often without fully understanding the trade-offs.

“When you enroll in a Medicare Advantage plan, you’re assigning your Part A and B benefits to a private insurer,” said Jason Rubin, a Medicare insurance specialist. “That company then controls where you go for care.”

Unlike Original Medicare, Medicare Advantage plans are network-based. You may need:

Referrals to see specialists
Prior authorization for procedures
In-network providers only, which can limit your doctor choices

If you have multiple specialists, they must all be in the same network or you risk denied claims and surprise bills. Don’t rush your Medicare decision. Compare Original Medicare + Medigap vs. Medicare Advantage carefully. Your choice affects doctor access, flexibility, and long-term coverage options.

Unlike Original Medicare, Medicare Advantage plans come with network restrictions and gatekeeping rules. Enrollees must: Use in-network providers, Get prior authorization for many procedures, Often obtain referrals before seeing specialists. These limitations can delay care or restrict access to preferred doctors. Before switching to Medicare Advantage, review the plan’s network, referral rules, and authorization policies especially if you have ongoing health needs. Flexibility matters. Don’t trade it away without knowing the cost.

“Most people don’t realize that Medicare Advantage plans are network-based,” said Jason Rubin, a Medicare insurance specialist. “If you have four or five doctors say one primary and several specialists they all need to be in the same medical network. Otherwise, you risk denied claims, out-of-network charges, or needing to switch providers.”

This restriction is a key difference from Original Medicare, which allows broader access to doctors nationwide. Before enrolling in Medicare Advantage, check whether your current providers are in-network especially if you manage multiple conditions or rely on specialist care. Flexibility matters. Don’t lose it by accident.

Medicare Switching Myth: Why You Might Be Denied Medigap Later

Many retirees mistakenly believe they can freely switch between Medicare Advantage and Original Medicare at any time. While switching is technically allowed during open enrollment, there’s a critical catch: Medigap coverage isn’t guaranteed outside your initial enrollment window.

“People assume they can go back to Original Medicare and just add a Medigap policy later,” said David Lipschutz, attorney and co-director of the Center for Medicare Advocacy. “But that’s often not true. Medigap insurers can deny coverage based on pre-existing conditions it’s one of the few insurance types that still allows this.”

Here’s what you need to know:

You get a one-time Medigap open enrollment period: six months after you first enroll in Medicare Part B.
After that, insurers can reject your application or charge more based on your health.
In 2022, 42% of Original Medicare enrollees had Medigap, but many who wanted it later were turned away.

If you’re considering Medicare Advantage, understand the long-term trade-offs. You may lose access to Medigap if you switch back later. Always weigh doctor access, coverage flexibility, and future insurability before making your first move.

Medicare Open Enrollment Mistake: Why Skipping Plan Reviews Could Cost You

Many retirees miss a key opportunity each year: Medicare Open Enrollment (Oct. 15 Dec. 7). According to Brandy Bauer of the Northeast Iowa Agency on Aging, most people don’t review their Medicare Advantage or Part D drug plans, even though doing so could unlock better coverage or lower costs.

“Every autumn is a chance to re-evaluate your plan,” Bauer said. “But the vast majority don’t do it and they could save money or gain new benefits if they did.”

Why it matters:

Plans change annually—your premiums, drug coverage, and provider networks may shift.
New plans may offer better benefits or lower out-of-pocket costs.
Failing to compare could mean overpaying or losing access to preferred doctors or medications.

Don’t set your Medicare plan on autopilot. Use Open Enrollment to shop smarter, save more, and stay covered.

Avoid IRMAA Shock: How Roth Conversions and Asset Sales Can Spike Medicare Premiums

Many retirees unintentionally trigger higher Medicare Part B and Part D premiums by making strategic financial moves without realizing the long-term impact. The culprit? IRMAA, the Income-Related Monthly Adjustment Amount, which adds surcharges based on your income from two years prior to enrollment.

“If you do a large Roth conversion, cash out an IRA, realize capital gains, or sell a second home, you could push your MAGI over the threshold and face steep IRMAA penalties,” said Patrick Huey, CFP and founder of Victory Independent Planning.

In 2025:

The standard Part B premium is $185/month
Married couples with MAGI between $266,000–$334,000 pay an extra $185, totaling $370/month

Mark Stancato, CFP of VIP Wealth Advisors, emphasizes the need for multi-year projections: “Without that lens, what looks like a smart tax move can backfire quickly.”