Reviewed by the Help Dementia Editorial Team — our editors review every article for accuracy against guidance from the National Institute on Aging, the Alzheimer’s Association, and peer-reviewed sources.
Medicare pays 80 percent of the cost for FDA-approved dementia drugs through Part B coverage, with patients responsible for the remaining 20 percent coinsurance—though this is the standard Part B payment structure rather than a new policy beginning in March 2026. What’s important to understand is that as we move into 2026, thousands of Americans with early-stage Alzheimer’s disease are becoming eligible for these groundbreaking monoclonal antibody treatments, and knowing how Medicare coverage works is essential for managing your out-of-pocket costs. If you have a Medicare diagnosis of mild cognitive impairment or mild dementia due to Alzheimer’s disease, plus evidence of beta-amyloid plaque on your brain, you could qualify for medications like Leqembi (lecanemab) or Kisunla (donanemab)—with Medicare handling the majority of what these expensive treatments cost.
The financial impact of this coverage matters. Leqembi costs approximately $27,439 per year before insurance, while Kisunla runs around $32,000 annually. With Medicare covering 80 percent, your out-of-pocket costs would range from roughly $5,488 to $6,400 per year in coinsurance alone—before factoring in the $283 Medicare Part B deductible you must meet first. For many seniors, supplemental Medigap insurance can cover that 20 percent coinsurance entirely, potentially reducing your direct costs to just the deductible.
Table of Contents
- How Does Medicare’s 80 Percent Coverage Work for Dementia Drugs?
- Eligibility Requirements and Proof of Beta-Amyloid Plaque
- Which Dementia Drugs Does Medicare Currently Cover?
- What Are Your Real Out-of-Pocket Costs and How to Minimize Them?
- Important Limitations and Side Effects to Understand
- Navigating the CMS Registry Requirement and Finding Participating Doctors
- What Happens to Dementia Drug Coverage and Treatments in 2026 and Beyond?
- Conclusion
How Does Medicare’s 80 Percent Coverage Work for Dementia Drugs?
Medicare Part B—the portion of traditional Medicare that covers outpatient services and certain medications—applies a straightforward payment model to dementia medications. After you meet the annual Part B deductible ($283 in 2026), Medicare pays 80 percent of the Medicare-approved amount for these drugs, and you pay the remaining 20 percent coinsurance. This coinsurance continues indefinitely; there’s no out-of-pocket maximum that caps your costs for Part B services the way there is under Part D prescription drug coverage. The actual price you might see billed depends on whether your provider participates in Medicare and agrees to accept the Medicare-approved amount as payment in full.
Here’s a real-world example: A 72-year-old with Medicare receives a diagnosis of mild cognitive impairment due to Alzheimer’s and starts Leqembi. The drug is administered as an infusion, and the Medicare-approved amount for Leqembi’s annual course is roughly $27,439. After paying the $283 Part B deductible once per calendar year, she owes 20 percent coinsurance on the remaining treatment—about $5,431. Her Medigap Plan G supplemental insurance then covers that $5,431, leaving her with only the $283 deductible as her out-of-pocket cost. Without supplemental coverage, she would owe the full $5,431 annually.
Eligibility Requirements and Proof of Beta-Amyloid Plaque
To qualify for Medicare coverage of these dementia drugs, you must meet specific clinical criteria—and they’re more restrictive than many people expect. You need a diagnosis of mild cognitive impairment (MCI) or mild dementia stage due to Alzheimer’s disease. You must also have documented evidence of beta-amyloid pathology in your brain, typically confirmed through amyloid positron emission tomography (PET) scanning or cerebrospinal fluid testing. Additionally, your treating physician must participate in the CMS Amyloid Biomarker Testing and Monitoring Registry—a mandatory program for tracking patient outcomes and safety. This eligibility threshold is both a strength and a limitation.
The limitation: you cannot access these medications if you’ve progressed to moderate or severe dementia. The drugs are designed for early intervention, specifically to slow cognitive decline when administered in early stages. Many families discover this requirement too late, having waited to pursue diagnosis or treatment until symptoms become more pronounced. The registry requirement, while necessary for safety monitoring, adds an administrative burden that some rural or underserved areas struggle to support. Roughly 100,000 Americans are expected to be eligible for Leqembi by 2026, yet diagnosing and reaching all candidates remains challenging.
Which Dementia Drugs Does Medicare Currently Cover?
Two monoclonal antibody medications have received FDA approval and Medicare coverage: Leqembi (lecanemab) and Kisunla (donanemab). Leqembi, approved in January 2023 with accelerated review and later given full approval in July 2023, costs approximately $27,439 per year and requires infusions every two weeks. Kisunla, approved more recently with a price tag around $32,000 annually, uses a different dosing schedule—starting with weekly infusions and transitioning to monthly infusions once a target dose is reached. Both target amyloid-beta plaques believed to drive Alzheimer’s progression.
A third treatment, Aduhelm (aducanumab), received accelerated approval but was subsequently delisted from Medicare coverage in June 2021 after the agency determined insufficient evidence supported its clinical benefit. This serves as a cautionary reminder that Medicare approval can be withdrawn. Looking ahead, the FDA is expected to rule on Axsome Therapeutics’ AXS-05 on April 30, 2026—a drug targeting agitation associated with Alzheimer’s disease rather than core cognitive decline. If approved, it would represent an important expansion of treatment options for specific behavioral symptoms rather than disease modification itself.
What Are Your Real Out-of-Pocket Costs and How to Minimize Them?
Your actual out-of-pocket expenses depend heavily on whether you have supplemental Medigap coverage and which plan you choose. With Medigap Plan G or Plan N, your supplemental insurance covers the 20 percent coinsurance, leaving you responsible for only the $283 annual Part B deductible. Without supplemental coverage, you’ll owe the full 20 percent coinsurance year after year—between $5,488 and $6,400 annually depending on the drug. Some people find that number manageable; others find it becomes a barrier to continuing treatment.
Here’s an important comparison: A senior on Medicare with Medigap Plan G taking Leqembi pays $283 out-of-pocket per year. The same person without supplemental coverage pays $5,431 annually. A third person with only Original Medicare but high debt load or limited fixed income might delay seeking diagnosis or treatment to avoid these costs—despite the potential cognitive benefits from early intervention. This creates a troubling equity gap where access to dementia-slowing medications becomes tied to insurance status rather than clinical need. If you don’t have Medigap, explore whether state pharmaceutical assistance programs or patient assistance from the drug manufacturers offer help.
Important Limitations and Side Effects to Understand
These dementia medications are not without risks, and Medicare coverage does not mean they are right for everyone. Both Leqembi and Kisunla carry a black-box warning for amyloid-related imaging abnormalities (ARIA)—microscopic brain changes visible on MRI that can lead to headaches, vision changes, confusion, or in rare cases, serious brain swelling. Roughly 18 to 35 percent of patients on these drugs experience ARIA-E (edema), though most cases are asymptomatic and detected only on routine brain imaging. Some patients develop ARIA-H (microhemorrhages), which occasionally causes concerning symptoms.
Doctors screen for ARIA risk through baseline MRI and subsequent brain imaging at regular intervals—costs covered under Medicare but nonetheless adding to the total burden of care. Patients must commit to ongoing infusions, regular clinic visits, and periodic MRI scans for monitoring. Some people with early Alzheimer’s opt not to pursue treatment because they want to avoid the frequent medical appointments, the risk of adverse events, or the uncertainty around long-term cognitive outcomes. There is also no guarantee that a given individual will experience the degree of cognitive slowing shown in clinical trials—some patients see modest benefit, while others see none.
Navigating the CMS Registry Requirement and Finding Participating Doctors
Not every neurologist, primary care physician, or memory care clinic participates in the CMS Amyloid Biomarker Testing and Monitoring Registry. Before pursuing diagnosis and treatment, you need to verify that your doctor is registered with CMS and cleared to prescribe these medications under Medicare. Some patients discover after diagnosis that their preferred provider isn’t registered—forcing a difficult choice between switching doctors or losing coverage.
The registry requirement exists for safety and data collection, but it does create friction in access. To find a participating provider, visit the CMS website or call Medicare directly at 1-800-MEDICARE. Ask whether the clinic or neurologist participates in the amyloid biomarker registry and whether they have experience administering Leqembi or Kisunla infusions. Teaching hospitals and large medical centers are more likely to participate than small private practices, particularly in rural areas where specialized neurology care is scarce.
What Happens to Dementia Drug Coverage and Treatments in 2026 and Beyond?
represents a pivotal year for dementia treatment access. The Axsome Therapeutics AXS-05 FDA decision on April 30, 2026 could expand the toolkit for managing Alzheimer’s-related behavioral symptoms if approved. Meanwhile, the population of eligible patients is expected to grow as more people receive early-stage Alzheimer’s diagnoses—potentially reaching 100,000 Americans by 2026. This expansion will test whether the healthcare system can accommodate increased demand for amyloid biomarker testing, neuroimaging, infusion center capacity, and monitoring.
Looking further ahead, additional monoclonal antibodies and novel treatment approaches are in clinical trials. The landscape of dementia treatment is evolving toward earlier intervention and combination therapies, though none have yet received FDA approval and Medicare coverage. The cost and complexity of care may eventually shift as treatments become routine, imaging requirements standardize, and infusion infrastructure expands. For now, the 80 percent Medicare payment structure remains the baseline, though patient access remains gated by eligibility criteria, provider participation, and the challenges of early diagnosis.
Conclusion
Medicare’s standard 80 percent coverage of FDA-approved dementia medications like Leqembi and Kisunla represents significant financial support for seniors pursuing early Alzheimer’s treatment—but it is not a new policy starting in March 2026. Rather, it reflects how Medicare Part B has traditionally paid for outpatient drugs and services. Your out-of-pocket costs will depend heavily on whether you have Medigap supplemental insurance, ranging from just the $283 annual Part B deductible (with Plan G or Plan N) to $5,000-plus annually if you’re uninsured. Eligibility is tightly defined: you must have mild cognitive impairment or mild dementia due to Alzheimer’s, proven beta-amyloid pathology, and access to a doctor participating in the CMS registry.
If you or a family member has noticed early memory changes, the next step is seeking an evaluation from a neurologist or memory care specialist who participates in the Medicare system. Understand your supplemental insurance options before diagnosis, because that coverage decision will shape your actual out-of-pocket costs for years to come. These medications offer a genuine opportunity to slow cognitive decline in early Alzheimer’s, but they require careful planning, ongoing medical monitoring, and realistic expectations about their benefits and risks. Talk with your doctor about whether you’re a candidate, understand the financial implications for your specific insurance situation, and make an informed decision about whether early treatment aligns with your health goals and values.
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For more, see NIH MedlinePlus — cognitive testing.
