Turning 65? Five Medicare Choices That Can Affect Your Coverage and Costs

Medicare decisions can affect both the coverage you receive and what you pay. The tricky part is that advice about enrolling at 65 can sound contradictory: some people need to sign up then, while others may be able to delay certain parts. Plan options, employer coverage and income rules all matter, so a decision that works for one person may not fit another.

Here are five common Medicare missteps to watch for, along with the details that can help you assess your own situation.

1. Assuming enrollment happens automatically

Some people are enrolled in Medicare automatically, but that doesn’t mean every part of their coverage is arranged for them. If you’ve been receiving retirement benefits for at least four months before turning 65, you’ll generally be enrolled in Medicare Parts A and B. Your Medicare card should arrive a few months before your birthday.

Other people need to take action themselves. And even when Parts A and B start automatically, that enrollment doesn’t sign you up for a private plan to help pay costs Medicare leaves to you. You’ll still need to consider whether to use Medicare Advantage or original Medicare with a Medigap supplement, then enroll in the coverage you choose.

There can also be a reason to delay Part B. If you have health insurance based on current employment at a company with 20 or more employees, you may be able to postpone enrolling. Check with your employer’s benefits administrator first. How the employer plan coordinates with Medicare can affect whether delaying Part B makes sense for your circumstances.

2. Mistaking other coverage for active employer insurance

Having an insurance card doesn’t necessarily mean you can delay Medicare enrollment. Retiree health benefits and COBRA generally aren’t treated as coverage from current employment for this purpose. If your insurance comes from a former job, don’t assume it gives you the same option as a plan based on your or your spouse’s active work.

TRICARE has its own requirements. People eligible for both TRICARE and Medicare Part A generally need Part B to keep TRICARE coverage, according to TRICARE. Check the requirements that apply to your situation before deciding when to enroll.

The key question is whether your coverage comes from current employment, rather than whether you still have a plan connected to a workplace. Confirm the details with your employer or benefits administrator before your Medicare enrollment window arrives.

3. Mixing up Medicare’s parts and plan choices

Medicare’s parts cover different services, and supplemental coverage works differently from a Medicare Advantage plan. Knowing what each option does helps clarify both the protection it offers and the costs you may still face.

Part A covers inpatient hospital care, skilled nursing facility care, hospice care and some home health care. Many people pay no monthly premium for Part A because they, or a spouse, worked and paid Medicare payroll taxes for 40 quarters—about 10 years. That doesn’t make care free: deductibles, copayments and coinsurance can still apply.

Part B helps pay for doctor visits, outpatient care and preventive services, including screenings, vaccines and annual wellness visits. The source lists the standard monthly premium as $202.90. People with higher incomes may pay more through an Income-Related Monthly Adjustment Amount, or IRMAA. Part B also has a deductible, and after meeting it, patients generally pay 20% of the Medicare-approved amount for covered services.

Part D helps pay for prescription drugs. Drug coverage is often included in Medicare Advantage plans. With original Medicare and Medigap, people generally buy Part D separately unless they have other creditable prescription coverage.

Medigap, also called Medicare Supplement Insurance, can help pay certain out-of-pocket costs for services that original Medicare covers. It doesn’t replace Medicare’s coverage; it helps with some of the costs Medicare leaves to the patient. The policies generally carry a separate monthly premium.

Medicare Advantage, or Part C, is an alternative to original Medicare. A private insurer offers a plan that combines Part A and Part B coverage, and often includes Part D. Some plans have low or even $0 monthly plan premiums. Enrollees still generally pay the Part B premium, and may also have deductibles and copayments. Plans can have specific provider networks, too.

In short, comparing only monthly plan premiums can leave out important details. Consider how a plan handles providers, prescriptions and out-of-pocket costs as well as what it charges each month.

4. Overlooking how past income can affect current premiums

Part B’s monthly premium surprises some new enrollees. Higher-income people can also face an IRMAA surcharge, which may be based on income from two years earlier. That timing can catch retirees off guard: income earned while working may affect Medicare costs after they’ve stopped working.

The example in the source involves a couple whose income was high enough two years earlier to make both spouses’ Medicare premiums roughly twice the usual amount. The husband had since retired, reducing the couple’s income. They asked for a new IRMAA determination based on retirement and their lower income, and their combined premiums fell by roughly $5,000 for that year.

A work stoppage is among the life-changing events that can be considered when asking for a new determination. If your current income is lower than it was during the year used to calculate your surcharge, review the appeal process and ask whether your circumstances qualify. The Social Security Administration explains the request process at ssa.gov/medicare/lower-irmaa.

Income choices can have effects beyond the year they occur. Wages, Roth conversions or stock sales may influence later Medicare costs. That makes it useful to consider Medicare premiums alongside other retirement decisions, rather than looking at each in isolation.

5. Letting a Medicare Advantage or drug plan roll over without a review

Medicare Advantage and Part D plans can change from one year to the next. Premiums, provider networks, pharmacies, benefits and provider lists may all be different. A plan that suited your needs this year might work differently the next year, even if your own health and prescriptions haven’t changed.

Open enrollment runs from October 15 through December 7. During this period, review your current plan’s terms for the coming year and compare them with the other options available where you live. Check whether your prescriptions and providers are included, and consider the plan’s costs and benefits against your needs and budget.

Availability varies by location. In September 2026, the Medicare Plan Comparison Tool showed 81 options near the source author in Wisconsin: 39 Medicare Advantage plans, 10 prescription drug plans and 32 Medigap options. Those figures illustrate how many choices can exist in one area; they aren’t a count for every location.

Five checks to make

• Confirm your enrollment timing. Find out whether you’ll be enrolled automatically and whether delaying Part B is an option.
• Check how your existing insurance coordinates with Medicare. Confirm whether it’s based on current employment and ask about the rules that apply to you.
• Compare the coverage types. Understand what Parts A, B and D cover, and how Medicare Advantage and Medigap differ.
• Review income-related costs. Find out whether past income affects your current premium and whether a change in circumstances may qualify you to request a new determination.
• Revisit your plan each year. Check plan terms, prescriptions, providers and costs during open enrollment.

Medicare offers several routes to coverage, and the details can change what you pay and which services or providers are available to you. Verify your enrollment and plan information before making a decision, then review your coverage each year as your needs and plan options evolve.