Turning 65 can bring a flood of Medicare information, insurance mail, deadlines, and unfamiliar terminology.
Unfortunately, some Medicare decisions cannot be made based on age alone. Your employment status, employer coverage, prescription coverage, Health Savings Account, doctors, medications, budget, and preferred way of receiving care can all affect the choices you make.
Common Medicare mistakes include assuming enrollment is automatic, missing an enrollment window, delaying Part B for the wrong reason, overlooking prescription drug coverage, and choosing a coverage option based only on its monthly premium.
Understanding these seven mistakes can help you ask better questions and make better-informed Medicare decisions.
Written and reviewed for accuracy by: Medicare Questions Answered Editorial Team
Published: November 1, 2026
Last reviewed: November 1, 2026
Editorial standards: Editorial & Fact-Checking Policy
Key Takeaways
Medicare enrollment is not automatic for everyone.
Your Initial Enrollment Period generally lasts seven months.
Not every type of health coverage allows you to delay Part B without a penalty.
Prescription drug coverage matters even if you take few medications today.
Medicare enrollment can affect your ability to contribute to a Health Savings Account.
The Medigap Open Enrollment Period is a one-time opportunity—not an annual event.
Monthly premium is only one factor to consider when comparing Medicare coverage.
Mistake 1: Assuming Medicare Enrollment Is Automatic
Some people are automatically enrolled in Medicare Part A and Part B when they turn 65, but others must sign up.
You are generally enrolled automatically if you have been receiving Social Security or Railroad Retirement Board benefits for at least four months before turning 65. Medicare usually mails your welcome package and Medicare card approximately three months before coverage begins.
If you are not already receiving those benefits, you may need to enroll through Social Security.
Do not assume that a Medicare card will simply arrive. Several months before turning 65, confirm whether you will be enrolled automatically or need to take action.
Mistake 2: Missing Your Initial Enrollment Period
For most people becoming eligible at age 65, the Initial Enrollment Period—also called the IEP—lasts seven months:
Three months before the month you turn 65
The month you turn 65
Three months after the month you turn 65
The date your coverage begins can depend on when you enroll. Missing the appropriate enrollment window may result in delayed coverage, a late-enrollment penalty, or both.
A useful way to remember the IEP is:
Three months before + your birthday month + three months after = seven months
If your birthday falls on the first day of a month, your Medicare timing may shift one month earlier.
Do not wait until the last day of your enrollment period to begin researching your options. Start learning how Medicare works several months before your 65th birthday.
Mistake 3: Delaying Part B Without Confirming Your Employer Coverage
You may be able to delay Medicare Part B if you or your spouse are still actively working and you have qualifying group health coverage based on that current employment.
However, not every type of health coverage is treated the same.
COBRA, retiree coverage, and Marketplace coverage generally do not extend the Part B Special Enrollment Period in the same way as coverage based on current employment. If you delay Medicare Part B because you have group health coverage based on current employment, you generally have an eight-month Special Enrollment Period after the employment or that job-based coverage ends, whichever happens first. COBRA does not extend this eight-month period.
Employer size can also affect how the coverage coordinates with Medicare:
If the employer has 20 or more employees, the group health plan generally pays first and Medicare pays second.
If the employer has fewer than 20 employees, Medicare generally pays first and the group health plan pays second.
Before delaying Part B, ask the employer’s benefits administrator:
Is my coverage based on current employment?
Does the employer plan require me to enroll in Medicare?
Which coverage will pay first?
How many employees does the employer have?
What happens to my coverage when employment ends?
Do I Need Medicare If I’m Still Working?
Mistake 4: Ignoring Prescription Drug Coverage Because You Take Few Medications
You may not take many prescription medications today, but that does not mean Part D can be ignored.
After your Initial Enrollment Period ends, going 63 consecutive days or longer without Medicare drug coverage or other creditable prescription drug coverage may result in a Part D late-enrollment penalty if you enroll later.
Creditable drug coverage is coverage expected to pay, on average, at least as much as standard Medicare drug coverage. An employer, union, TRICARE, Indian Health Service, or Department of Veterans Affairs plan may provide creditable coverage, but the plan should tell you whether it qualifies.
Keep every creditable-coverage notice you receive. You may need it later to show that you maintained qualifying prescription coverage.
When comparing drug coverage, review more than the monthly premium. Also check:
Whether your medications are on the plan’s formulary
The cost-sharing tier for each medication
Whether your preferred pharmacy is in the network
Whether prior authorization, quantity limits, or step therapy apply
Mistake 5: Continuing HSA Contributions After Medicare Coverage Begins
Enrolling in Medicare affects your eligibility to contribute to a Health Savings Account, commonly called an HSA.
Beginning with the first month you are enrolled in Medicare, your HSA contribution limit becomes zero. This rule also applies to months covered by retroactive Medicare enrollment.
This can be especially important for someone who delays Medicare beyond age 65.
When a person enrolls in premium-free Part A after age 65, Part A coverage may be retroactive for as many as six months—but not earlier than the person’s first month of Medicare eligibility. HSA contributions made during a retroactively covered month may be considered excess contributions.
Medicare advises people who are working past 65 and contributing to an HSA to consider stopping contributions six months before applying for Medicare or Social Security benefits.
Because HSA rules involve tax consequences, coordinate your Medicare timing with:
Your employer’s benefits administrator
Your HSA administrator
Social Security
A qualified tax professional
Do not enroll in Part A simply because it is premium-free without first understanding how enrollment may affect your HSA contributions.
Mistake 6: Assuming Medigap Open Enrollment Happens Every Year
Medicare Supplement Insurance—also called Medigap—can help pay certain costs left by Original Medicare.
Federal law provides a one-time, six-month Medigap Open Enrollment Period. It begins the first month that you are both:
Age 65 or older; and
Enrolled in Medicare Part B
During that period, an insurer generally cannot refuse to sell you a Medigap policy it offers, use medical underwriting to deny your application, or charge you more because of a pre-existing health problem.
After this period, depending on your state and circumstances:
Fewer policies may be available.
A policy may cost more.
An insurer may use medical underwriting.
An insurer may deny an application unless a guaranteed-issue right applies.
The Medigap Open Enrollment Period is not the same as Medicare’s fall Open Enrollment Period. It does not automatically repeat every year.
Medigap or Medicare Supplement Insurance
Mistake 7: Choosing Coverage Based Only on the Monthly Premium
A low or $0 plan premium can be attractive, but premium alone does not tell you what healthcare may cost during the year.
When comparing Original Medicare and Medicare Advantage, consider:
Whether your doctors and hospitals participate
Whether your medications are covered
Deductibles, copayments, and coinsurance
Provider networks
Specialist referrals
Prior-authorization requirements
Travel and out-of-area coverage
Maximum out-of-pocket exposure
Whether Medigap is available and appropriate
With Original Medicare, you can generally use any provider in the United States that accepts Medicare, and referrals are generally not required. Original Medicare by itself does not have a built-in annual maximum on Part A and Part B out-of-pocket costs.
Medicare Advantage plans may use provider networks, referrals, and prior authorization. They do include an annual maximum out-of-pocket limit for covered Part A and Part B services.
A plan with a lower premium could still cost more overall if:
Your doctors are outside the network.
Your medications have higher cost sharing.
You use healthcare frequently.
The plan has a high out-of-pocket maximum.
You regularly need out-of-area care.
The best comparison is not simply premium versus premium. It is how the entire coverage structure fits your healthcare needs and preferences.
Questions to Ask Before Turning 65
Use this checklist before making Medicare decisions:
Will I be enrolled automatically, or do I need to sign up?
When does my Initial Enrollment Period begin and end?
Is my current insurance based on active employment?
Which coverage will pay first?
Is my prescription drug coverage creditable?
Am I contributing to an HSA?
When should my HSA contributions stop?
Do my doctors accept Medicare?
Are my medications covered?
Do I want Original Medicare or Medicare Advantage?
Should I consider Medigap?
What could my total annual out-of-pocket costs be?
Will I need coverage while traveling?
What enrollment deadlines apply to my situation?
Do not rely only on a coworker’s, friend’s, or relative’s Medicare experience. Their employment, prescriptions, doctors, financial situation, and coverage needs may be different from yours.
Frequently Asked Questions
Do I Have to Enroll in Medicare at 65?
Not necessarily.
If you or your spouse are still working and you have qualifying group health coverage based on current employment, you may be able to delay Part B without a late-enrollment penalty.
The correct decision depends on the type of employer coverage, employer size, which plan pays first, and whether you contribute to an HSA. Confirm the details with the employer’s benefits administrator before delaying enrollment.
Can I Keep Contributing to an HSA After I Enroll in Medicare?
No.
Beginning with the first month you are enrolled in Medicare, your HSA contribution limit is zero. Retroactive Medicare coverage can also make earlier contributions excess contributions.
Do I Need Part D If I Do Not Take Any Prescriptions?
You are not required to enroll in Part D, but delaying it without other creditable prescription drug coverage could result in a late-enrollment penalty if you enroll later.
Consider both your current medications and the possibility that your prescription needs may change.
Can I Buy Medigap at Any Time?
You can apply for a Medigap policy at other times, but you may not have the same federal protections available during your six-month Medigap Open Enrollment Period.
Outside that period, an insurer may be permitted to use medical underwriting, charge more, or deny an application unless a guaranteed-issue right or additional state protection applies.
Is a $0-Premium Medicare Advantage Plan Free?
No.
A $0 plan premium means the plan does not charge an additional monthly premium. You must generally continue paying the Medicare Part B premium, and the plan may still have deductibles, copayments, coinsurance, prescription costs, and an annual out-of-pocket maximum.
The Bottom Line
The most important Medicare decisions involve more than simply turning 65.
You need to understand:
Whether enrollment is automatic
Which deadlines apply
How employer coverage coordinates with Medicare
Whether your prescription coverage is creditable
How enrollment affects HSA contributions
When Medigap protections apply
How total costs differ between coverage paths
Starting early gives you time to ask questions, verify your coverage, and avoid rushed decisions.
Medicare Questions Answered is here to help you understand the fundamentals before you choose coverage.
Related Medicare Topics
Need Personalized Medicare Help?
General Medicare education is an important first step, but your employment, doctors, medications, budget, and other coverage may affect your individual options.
When you request assistance, Medicare Questions Answered can connect you with one licensed insurance professionalwho can discuss your individual Medicare situation.
Sources
Medicare.gov — How Do I Sign Up for Medicare?
Medicare.gov — When Does Medicare Coverage Start?
Medicare.gov — Working Past 65
Medicare.gov — Who Pays First?
Medicare.gov — Creditable Prescription Drug Coverage
Medicare.gov — Medicare Part D Costs and Late-Enrollment Penalty
Internal Revenue Service — Publication 969: Health Savings Accounts
Medicare.gov — Your Medigap Open Enrollment Period
Medicare.gov — Compare Original Medicare and Medicare Advantage