Medicare Pitfalls and Potential Enrollment Problems

Medicare is one of the most important retirement planning issues you need to get right. It affects your health coverage, your cash flow, your tax planning, your retirement timing, and in some cases your spouse’s coverage as well.

The difficult part is that Medicare is not a single decision. You may need to decide when to enroll, whether to stay with Original Medicare or choose Medicare Advantage, whether to buy a Medigap policy, how to handle prescription drug coverage, and how Medicare coordinates with employer, retiree, COBRA, or other coverage.

This article is not intended to be a complete guide to every Medicare decision. It is a practical planning checklist of issues that can cause unnecessary costs, coverage gaps, or unpleasant surprises.

If you are also reviewing Social Security, be sure to coordinate the two decisions. Social Security and Medicare often overlap, but the rules are not the same.

Start with the big picture

Before choosing coverage, understand the two main Medicare paths:

Original Medicare

Includes Part A for hospital insurance.
Includes Part B for medical insurance.
Allows you to use any doctor, hospital, or provider that accepts Medicare.
Does not include most prescription drug coverage, so many people add a Part D drug plan.
Does not have a built-in annual out-of-pocket maximum for all medical costs.
Many people add a Medigap, also called Medicare Supplement, policy to help cover deductibles, copayments, and coinsurance.

Medicare Advantage

Also called Part C.
Offered by private insurance companies approved by Medicare.
Replaces Original Medicare as the way you receive Part A and Part B benefits.
Usually includes prescription drug coverage.
Often uses provider networks.
May require referrals or prior authorization for some services.
Has an annual out-of-pocket limit for covered Part A and Part B services.
May include extra benefits that Original Medicare generally does not cover, such as some dental, vision, hearing, transportation, wellness, or in-home support benefits.

There is no universally correct choice. The right answer depends on your doctors, prescriptions, travel plans, health history, cash flow, risk tolerance, and desire for flexibility.

Important Medicare enrollment points

Medicare does not provide family coverage.

Each person enrolls individually.
Your spouse’s Medicare timing may be different from yours.
One spouse going on Medicare may affect whether the other spouse can remain on employer coverage.

You generally enroll in Medicare Parts A and B through Social Security.

Medicare is administered by the Centers for Medicare & Medicaid Services.
Social Security handles most enrollment for Medicare Parts A and B.
You generally use Medicare.gov to compare and enroll in Medicare Advantage and Part D prescription drug plans.

Your first Medicare enrollment window is usually your Initial Enrollment Period.

This is generally a 7-month period.
It starts 3 months before the month you turn 65.
It includes the month you turn 65.
It ends 3 months after the month you turn 65.
If your birthday is on the first day of the month, your Medicare timing may be different, so check carefully.

Do not assume your coverage will start immediately.

The month you enroll can affect when your Medicare coverage begins.
Delaying enrollment until late in your Initial Enrollment Period can create a coverage gap.
This is especially important if your employer coverage or individual coverage is ending.

If you already receive Social Security benefits before age 65, you may be automatically enrolled.

Many people receiving Social Security before 65 are automatically enrolled in Medicare Parts A and B.
You should still review the Medicare card and effective dates carefully.
If you do not want Part B because you have qualifying employer coverage, follow the instructions from Social Security carefully.

Part A, Part B, Part C, Part D, and Medigap

Part A is hospital insurance.

Many people pay no premium for Part A because they or a spouse paid Medicare taxes long enough.
Part A helps cover inpatient hospital care, skilled nursing facility care under limited conditions, hospice care, and some home health care.
Part A is not the same as long-term custodial care.

Part B is medical insurance.

Part B helps cover doctor visits, outpatient care, preventive services, durable medical equipment, and certain other medical services.
In 2026, the standard Part B premium is $202.90 per month.
In 2026, the Part B deductible is $283.
After the deductible, you usually pay 20% of the Medicare-approved amount for covered Part B services if the provider accepts assignment.
Higher-income beneficiaries may pay an additional amount called IRMAA.

Part C is Medicare Advantage.

You must have both Part A and Part B to join a Medicare Advantage plan.
Medicare Advantage plans are offered by private insurers.
Many plans include Part D prescription drug coverage.
Many plans use provider networks.
Many plans offer extra benefits that Original Medicare does not cover, such as some dental, vision, hearing, transportation, and other supplemental benefits.
These extra benefits vary by plan and may change from year to year.

Part D is prescription drug coverage.

Part D is optional, but going without creditable prescription drug coverage can create a late enrollment penalty.
In 2026, no Medicare Part D deductible can be more than $615.
In 2026, out-of-pocket costs for Part D covered drugs are capped at $2,100.
The Medicare Prescription Payment Plan may allow you to spread covered drug out-of-pocket costs across the year, but it does not reduce the total cost of the drugs.

Medigap is Medicare Supplement insurance.

Medigap policies are sold by private insurers.
They help pay certain out-of-pocket costs under Original Medicare.
They do not work with Medicare Advantage plans.
Your best Medigap buying opportunity is usually your 6-month Medigap open enrollment period, which starts when you are 65 or older and enrolled in Part B.
During that period, insurers generally must sell you a policy regardless of health history.
After that period, you may face medical underwriting in many situations, depending on your state and circumstances.

Late enrollment can be expensive

Missing your enrollment window can create penalties and coverage gaps.

Part B penalties can last as long as you have Part B.
Part D penalties can also last as long as you have Part D coverage.
The longer you go without coverage, the larger the penalty may be.

The General Enrollment Period is not a perfect safety net.

If you miss your Initial Enrollment Period and do not qualify for a Special Enrollment Period, you may need to use the General Enrollment Period.
The General Enrollment Period runs from January 1 through March 31 each year.
Coverage generally begins the month after you enroll.
A late enrollment penalty may apply.

Part B late enrollment penalty.

In most cases, the Part B penalty is 10% for each full 12-month period that you could have had Part B but did not sign up.
This penalty is added to your monthly Part B premium.
It generally lasts for as long as you have Part B.

Part D late enrollment penalty.

You may owe a Part D penalty if you go 63 or more days in a row without Medicare drug coverage or other creditable prescription drug coverage after your Initial Enrollment Period.
Creditable coverage generally means coverage expected to pay, on average, at least as much as standard Medicare drug coverage.
Employer, union, VA, TRICARE, and other plans may or may not be creditable, so confirm in writing.

Working past age 65

Working past 65 can complicate Medicare enrollment.

You may be able to delay Part B if you have health coverage through active employment.
Coverage must usually be based on your active employment or your spouse’s active employment.
Retiree coverage and COBRA generally do not count as active employer coverage for delaying Part B without penalty.

Employer size matters.

If your employer has 20 or more employees, the employer plan is generally primary for workers age 65 or older.
If your employer has fewer than 20 employees, Medicare is generally primary.
If Medicare is primary and you fail to enroll, your employer plan may pay little or nothing.
Different rules may apply for disability-based Medicare, where the employer-size threshold is generally 100 employees.

Do not rely on informal employer guidance.

Ask the employer or benefits administrator whether the plan is primary or secondary to Medicare.
Ask whether the prescription drug coverage is creditable for Part D purposes.
Get important answers in writing.

Special Enrollment Period for Part B.

If you delayed Part B because you had qualifying active employer group health plan coverage, you may qualify for a Special Enrollment Period.
This period generally allows you to sign up while still covered by the employer plan or during the 8 months after the employment or group health plan coverage ends, whichever comes first.
Waiting too long can create a coverage gap and possibly a penalty.

Update: Part B Special Enrollment Period applications can now be handled online.

In the past, this process was largely paper-based.
Social Security now allows qualifying individuals to apply online for Part B during a Special Enrollment Period when employer group health plan coverage is ending.
You may still need employer documentation, such as evidence of group health plan coverage.
Keep copies of everything you submit.

COBRA, retiree coverage, and individual coverage

COBRA can be a trap.

COBRA is not active employer coverage.
If you are Medicare-eligible and rely on COBRA instead of enrolling in Part B, you may face penalties or coverage gaps.
COBRA drug coverage may be creditable for Part D, but you should verify this before relying on it.

Retiree health coverage can also be a trap.

Retiree coverage is generally secondary to Medicare.
Many retiree plans assume you have Medicare Parts A and B when eligible.
Failing to enroll in Medicare may leave you with unpaid claims.

Marketplace coverage is not a reason to delay Medicare.

Individual Marketplace coverage is not active employer coverage.
Once you are eligible for premium-free Part A, you generally should not rely on Marketplace coverage as a substitute for Medicare.

Health Savings Accounts and Medicare

Medicare enrollment affects HSA contributions.

Once you are enrolled in Medicare, you can no longer contribute to a Health Savings Account.
You can still use existing HSA funds for qualified medical expenses.

Part A can be retroactive.

If you enroll in premium-free Part A after age 65, your Part A coverage may be retroactive for up to 6 months, but not earlier than the month you first became eligible for Medicare.
This retroactive coverage can make HSA contributions for that period ineligible.
To avoid a tax problem, many people stop HSA contributions at least 6 months before applying for Medicare or Social Security benefits.

Social Security can trigger Medicare Part A.

If you are age 65 or older and apply for Social Security benefits, you generally must take Medicare Part A if you are eligible for premium-free Part A.
This can affect HSA planning even if you intended to keep working.

Higher-income Medicare premiums

IRMAA can increase Medicare premiums.

IRMAA stands for Income-Related Monthly Adjustment Amount.
It can apply to Part B and Part D.
It is based on modified adjusted gross income from your tax return, generally from 2 years earlier.
For example, 2026 IRMAA is generally based on 2024 income.

Retirement can create a mismatch.

If you retire in 2026, your Medicare premiums may still be based on income from 2024.
That can be frustrating if your current income has dropped.

You may be able to appeal IRMAA after certain life-changing events.

Examples may include retirement, reduction in work hours, death of a spouse, divorce, loss of pension income, or certain other events.
The appeal is handled through Social Security, not directly through Medicare.

Medicare Advantage considerations

Medicare Advantage plans can be attractive, but they require careful review.

Premiums may be low.
Drug coverage may be included.
Dental, vision, hearing, transportation, fitness, and other supplemental benefits may be included.
There is an annual out-of-pocket limit for covered Part A and Part B services.

The tradeoff is that plan rules matter.

You may need to use network doctors and hospitals.
Out-of-network care may cost more or may not be covered, depending on the plan.
Some services may require prior authorization.
Plans can change costs, networks, formularies, and benefits from year to year.

Update: Some Medicare Advantage plans may offer broader supplemental benefits.

Medicare Advantage plans may include supplemental benefits that Original Medicare does not cover.
Examples can include dental, vision, hearing, transportation to medical appointments, in-home support, home safety modifications, and other services.
These benefits are plan-specific.
Do not assume that a benefit exists just because another Medicare Advantage plan offers it.
Review the Evidence of Coverage before enrolling.

What Original Medicare generally does not cover

Original Medicare does not cover everything. Common gaps include:

Most long-term custodial care.
Most dental care.
Dentures in most cases.
Routine eye exams for glasses.
Eyeglasses in most cases.
Hearing aids and exams for fitting hearing aids.
Routine foot care in most cases.
Cosmetic surgery in most cases.
Most care outside the United States.
Many personal care and home support services.

Some Medicare Advantage plans or Medigap policies may provide limited coverage for certain services, but the details vary.

Practical Medicare checklist

Before you enroll, gather and review:

Your expected retirement date.
Your current health insurance type.
Whether your current coverage is through active employment, retiree coverage, COBRA, Marketplace coverage, VA, TRICARE, FEHB, or another source.
Whether your employer has 20 or more employees.
Whether your drug coverage is creditable.
Your doctors, specialists, hospitals, and preferred pharmacies.
Your current prescriptions, dosages, and pharmacy preferences.
Whether you travel frequently or live in more than one state during the year.
Whether you want the flexibility of Original Medicare or are comfortable with a Medicare Advantage network.
Whether you want or need a Medigap policy.
Whether you are still contributing to an HSA.
Whether your income may trigger IRMAA.
Whether you have had a recent life-changing event that may support an IRMAA appeal.

Where to get help

Medicare decisions can be complex, and mistakes can be expensive. Consider using multiple sources before making a final decision:

Medicare.gov for official Medicare information and plan comparisons.
Social Security for enrollment in Medicare Parts A and B.
Your employer benefits department if you are still working.
Your retiree benefits administrator if you have retiree coverage.
Your State Health Insurance Assistance Program, known as SHIP, for free Medicare counseling.
A qualified Medicare insurance professional for plan-specific guidance.
Your financial advisor for how Medicare timing, premiums, taxes, HSA contributions, and retirement income planning fit together.

This article is not insurance advice and is not intended to recommend a specific Medicare Advantage, Part D, or Medigap policy. It is intended to help you identify the Medicare issues that should be reviewed before you make a decision.

Medicare Pitfalls and Enrollment Problems

What you don't know can cost you dearly