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Medicare Basics: Eligibility, Enrollment, Costs, Deadlines, and Annual Review

Medicare is a federal health insurance program for people 65 and older, and for some younger people with disabilities, including early-onset dementia. It can feel overwhelming, but understanding when to enroll, what each part covers, and why you must review plans every year can save you money and stress. You have concrete steps you can take right now to get started, avoid costly penalties, and make sure your loved one has the right coverage.

Key points

  • Enroll in Medicare during the seven-month window around your 65th birthday to avoid lifelong late penalties.
  • Review your Medicare plan every year during open enrollment (Oct 15–Dec 7) because plans change—drugs, costs, and networks can shift.
  • Original Medicare (Parts A and B) plus a Part D drug plan and Medigap gives you the most flexibility to see any doctor who accepts Medicare.
  • Medicare Advantage plans (Part C) often include drug coverage and extra benefits like dental and vision, but have network restrictions.
  • If you are caring for someone with early-onset dementia, apply for Medicare disability immediately—it can be fast-tracked.
  • Use free resources like medicare.gov, SHIP counselors, and the Medicare & You handbook to make informed decisions without paying a broker.

What Is Medicare and Who Is Eligible?

Medicare is a government-sponsored health insurance program that primarily covers people age 65 and older. It also covers younger people who qualify for Social Security due to a disability, including those diagnosed with early-onset dementia. In fact, a diagnosis of early-onset dementia can fast-track someone for Medicare disability benefits within a few months, rather than waiting until age 65. Medicare is an entitlement program—you or your spouse have paid into it through payroll taxes, so you are entitled to these benefits when you meet the eligibility criteria.

The Parts of Medicare: What They Cover

Medicare is divided into parts. Part A is hospital insurance and helps pay for care in a hospital, skilled nursing facility, nursing home, or hospice. It covers room, board, and facility charges. For most people, Part A is free at age 65. Part B covers professional services from doctors and other healthcare providers, outpatient services like X-rays and lab work, and durable medical equipment. Part B is voluntary and requires a monthly premium. In 2024, the Part B deductible is $240, and after that you typically pay 20% of the Medicare-approved amount for most services. Part D covers prescription drugs. Many people choose a Medicare Advantage plan (Part C), which combines Parts A, B, and often D into one plan offered by private insurance companies. Original Medicare (Parts A and B) can be supplemented with a Medigap policy to help with out-of-pocket costs.

When to Enroll: Deadlines You Cannot Miss

The initial enrollment period is a seven-month window that starts three months before the month you turn 65, includes your birthday month, and ends three months after. If you miss this window, you may face late enrollment penalties that last as long as you have Medicare. There is also a special enrollment period if you or your spouse are still working for a large employer (20 or more employees) and have group health coverage. Once that coverage ends, you have eight months to sign up for Part B without penalty. The annual open enrollment period runs from October 15 to December 7 each year. During this time, you can change or add to your Medicare plan, and any changes take effect January 1. There is also a Medicare Advantage open enrollment period from January 1 to March 31, during which you can switch from one Advantage plan to another or return to Original Medicare.

Why You Must Review Plans Every Year

Insurance plans change their formularies (lists of covered drugs), premiums, deductibles, and network providers every year. A plan that was a good fit last year may not cover your loved one's medications or preferred doctors this year. The annual enrollment period (October 15 to December 7) is your chance to compare plans and switch if needed. Many caregivers make the mistake of assuming their current plan is still the best option, only to find out in January that a critical drug is no longer covered or that costs have jumped. Reviewing plans annually ensures you are not overpaying and that your loved one's care needs are still met.

General caregiving information, not medical advice. Check medications and major care changes with your clinician.

Step-by-step

  1. Confirm eligibility and mark the initial enrollment window: if the person is 65 or older—or under 65 with early-onset dementia—they likely qualify. For early-onset dementia, apply for Social Security disability benefits, which can fast-track Medicare. Then note the seven-month window starting three months before the month they turn 65.

  2. Choose between Original Medicare and Medicare Advantage: use the Plan Finder at medicare.gov to compare costs, networks, and drug coverage. If choosing Original Medicare, consider adding a Part D drug plan and a Medigap policy during the six-month window after Part B starts.

  3. Complete the CMS-10106 Authorization to Disclose Personal Health Information form from medicare.gov so Medicare can speak with you about the beneficiary’s account. Submit it early.

  4. Set up a Medicare online account at medicare.gov to view claims, pay premiums, and manage plans. Share the new Medicare ID with their doctors and pharmacy.

  5. Review plans each year during open enrollment (October 15–December 7): check medication coverage, in-network doctors, and cost changes. Switch by December 7 for January 1 coverage; confirm activation with the new plan in early January.

  6. If the person is still working and covered by an employer plan with 20+ employees, Medicare is secondary and Part B can be delayed without penalty. Enroll in Part B within eight months of that coverage ending to avoid a lifetime penalty.

What not to do

  • Don't miss the initial enrollment window: late penalties last a lifetime—10% surcharge on Part B for every 12 months eligible without enrolling, plus 1% per month on Part D if without drug coverage.

  • Don't assume Medicare covers everything: Original Medicare generally excludes long-term care, dental, vision, and hearing aids. Consider a Medicare Advantage or supplemental policy if needed.

  • Don't skip the CMS-10106 form: without it, Medicare cannot discuss the account with you, causing delays.

  • Don't wait until late in open enrollment to start: the Plan Finder slows under heavy traffic in late November. Begin in mid-October.

  • Don't pass up the free Annual Wellness Visit: it includes a Health Risk Assessment and is covered once per year at no cost.

Practical tools

  • Medicare.gov Plan Finder

    Enter the beneficiary’s zip code, medications, and preferred pharmacy at medicare.gov/plan-compare to compare Part D and Medicare Advantage plans with estimated annual costs. Use every fall during open enrollment.

  • Authorization to Disclose Personal Health Information Form (CMS-10106)

    Available at medicare.gov. Provide the beneficiary’s Medicare number and your contact details, then submit by mail or through their online account so Medicare can speak with you.

  • Medicare & You Handbook

    Mailed each fall, this official handbook summarizes plan changes for the coming year. Download a PDF from medicare.gov if lost.

  • State Health Insurance Assistance Program (SHIP)

    Free, unbiased one-on-one counseling from local advisors. Call 1-877-839-2675 to find your nearest SHIP counselor.

  • Social Security Administration (for early-onset dementia)

    If under 65 with dementia, file for disability benefits at ssa.gov or a local office. Approval triggers Medicare eligibility and a separate seven-month enrollment window.

Discuss with your clinician

Ask your doctor if your loved one qualifies for a Medicare Annual Wellness Visit and whether a Health Risk Assessment is appropriate. This visit is free and can help identify health risks early.

If your loved one has early-onset dementia, ask their neurologist or primary care provider for documentation to support a disability application for Medicare. This can speed up the process.

Discuss with your clinician whether any planned treatments or therapies (like physical therapy or home health) are covered by Medicare Part B, and whether prior authorization is needed.

If considering hospice, ask the hospice medical director if they are board certified in hospice and palliative medicine, and confirm that the program is Medicare-certified.

Related guides

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