Lecanemab (brand name Leqembi) is a medicine for the early stage of Alzheimer's disease. It removes amyloid (a sticky protein that builds up between brain cells) from the brain. In a large study, it slowed the loss of memory and daily skills by a modest amount over 18 months.1,2
It is not a cure, and it does not bring back memory that is already lost.5 It also has real risks and a lot of appointments. This page helps families decide with the doctor whether it fits.
Key points
- Lecanemab is for people with mild cognitive impairment or mild dementia due to Alzheimer's, with amyloid confirmed by a test.2
- In the main trial, it slowed decline by about one quarter over 18 months. That is a real but small effect.2 Moderate evidence
- It can be given as an IV infusion every two weeks. Since July 2026, it can also be started as a weekly shot at home with a pen (Leqembi Iqlik).2,4
- Its main risk is ARIA, brain swelling or small bleeds. Regular MRI scans watch for it. People with two copies of the APOE e4 gene have the highest risk.2
- Medicare Part B can cover the IV form if your doctor enters you in an approved registry. You usually pay 20% after the deductible.7,8
What lecanemab does
Lecanemab is a monoclonal antibody (a lab-made protein that sticks to one specific target). It latches onto amyloid in the brain and helps the body clear it away.5 In the main trial, about 2 in 3 people (67%) had low amyloid after about a year and a half.2
Lowering amyloid seems to slow the disease a little, but it does not stop it. Older memory medicines like donepezil work differently. They ease symptoms for a while, and some people take both.
The FDA first approved lecanemab in January 2023 under a quicker path called accelerated approval. In July 2023, it became the first drug of its kind to get full (traditional) approval.3
What the trial showed, in plain numbers
The main study was called CLARITY AD. It included 1,795 people aged 50 to 90 with early Alzheimer's. Half got lecanemab every two weeks for 18 months. Half got a placebo (a look-alike with no medicine).1,3
Doctors measured change on a rating scale called the CDR-SB. It runs from 0 to 18. It covers memory, knowing time and place, judgment, community activities, home life and hobbies, and personal care. A higher score means more problems.2
| After 18 months | Lecanemab | Placebo |
|---|---|---|
| Average worsening on the CDR-SB (0–18 scale) | 1.21 points | 1.66 points |
| Difference | 0.45 points less worsening, about 27% slower | — |
| Infusion reactions (fever, chills, aches, headache) | about 1 in 4 people (26%) | 7% |
| ARIA swelling (ARIA-E) | about 1 in 8 people (13%) | 2% |
| ARIA small bleeds (ARIA-H) | 17% | 9% |
Source for the table: FDA label for Leqembi.2
What this means in daily life. Everyone in the trial got worse over 18 months. People on lecanemab got worse more slowly. Tests of thinking and of daily tasks also favored lecanemab by a similar amount.2 The study authors described the benefit as moderate.1
A slower decline may mean more time in the mild stage, when a person can still make choices and plan ahead. But a 0.45-point difference on an 18-point scale is small. Many families may not notice it day to day. Benefit beyond 18 months is still being studied.2
Who can get lecanemab
Lecanemab is approved to start only in people who:2,5
- Have mild cognitive impairment (MCI) or mild dementia caused by Alzheimer's disease. See mild cognitive impairment and early-stage dementia.
- Have amyloid confirmed by an amyloid PET scan, a spinal fluid test, or another approved test. See brain scans and spinal fluid tests.
It has not been tested in people with moderate or severe dementia, or in people with no symptoms.3,5
In May 2025, the FDA cleared the first blood test that helps show whether amyloid is likely present. It is for adults 55 and older with memory symptoms who are seen in a specialty clinic.9 It is not meant to be used alone. Your doctor will look at it with other test results, and may still order a PET scan or spinal fluid test.9 Read more about blood tests for Alzheimer's.
Who may not be a good fit. Expert advice from 2023 suggests doctors avoid lecanemab, or use great care, when a person has:6
- An MRI showing more than four tiny old bleeds, a larger past bleed, or a lot of small-vessel damage
- A need for blood thinners such as warfarin or apixaban (aspirin was allowed in the trial)
- A bleeding or clotting disorder
- Any past seizure, or a stroke or mini-stroke (TIA) in the past year
- Something that prevents MRI scans, such as some metal implants
Our page Are anti-amyloid treatments right for us? walks through this decision step by step.
How it is given: IV infusions or at-home shots
There are now two ways to take lecanemab. You can switch between them during treatment.2,4
IV infusion (Leqembi)
- Given through a vein at an infusion center or clinic
- About one hour each time, plus travel and check-in
- First 18 months: every two weeks
- After 18 months: can stay every two weeks or move to every four weeks
- Covered under Medicare Part B when the rules are met
Under-the-skin shot (Leqembi Iqlik)
- A quick shot under the skin with a pen-like autoinjector
- Each shot takes about 15 seconds
- Starting treatment: two shots once a week
- After 18 months: can stay on two shots or move to one weekly maintenance shot
- A health worker guides at least the first two doses
- Pens are kept in the refrigerator
The timeline of the at-home shot. In August 2025, the FDA approved the Iqlik pen only for maintenance, after 18 months of IV treatment. On July 13, 2026, the FDA approved it for starting treatment too. A person can now take lecanemab at home from the first dose.4,5
Computer models predict that the shot gives about the same drug levels and amyloid drop as the IV form. The two were not compared head to head in a large trial.2 Safety of the starting shot was judged mostly from IV data, plus a small group of 72 people.2 Redness, swelling, itching or bruising at the shot site are common.2,4
Who might choose the shot. It may help people who live far from an infusion center or have trouble with travel or mobility.4 Someone must store the pens, track doses and watch for side effects. Often a care partner gives the shot.
How long treatment lasts. The label does not set a fixed stopping point.2 This is different from donanemab. Ask your doctor how you will decide together when to stop, for example if the disease moves past the mild stage.
MRI monitoring
MRI scans are how doctors catch ARIA early, often before any symptoms. The FDA label calls for:2
- A recent MRI before the first dose
- MRIs at about 1, 2, 3 and 6 months after starting. The 1-month scan comes before the 3rd IV infusion or the 5th weekly shot.
- Extra MRIs any time new symptoms appear.
Expert advice also suggests another MRI around the one-year mark for people who carry APOE e4 or who had ARIA before.6 Most ARIA swelling shows up early, within the first several doses.2 Try not to skip a scheduled scan.
ARIA: brain swelling and bleeding
ARIA stands for amyloid-related imaging abnormalities. It comes in two kinds:2
- ARIA-E: swelling or fluid in part of the brain. It usually goes away in weeks to months.
- ARIA-H: tiny spots of bleeding, or a thin layer of old blood on the brain's surface.
Most people with ARIA feel nothing. It is found only on the MRI. About 3 in 100 people on lecanemab had symptoms from ARIA.2 Rarely, ARIA is serious or can be deadly. Bleeds larger than about 1 cm (less than half an inch) have happened, and some people have died.2 For this reason, lecanemab carries the FDA's strongest warning, a boxed warning.2,3
If ARIA shows up, the doctor may keep going, pause treatment until it clears, or stop for good. The choice depends on how large it looks on the MRI and whether there are symptoms.2
Watch for these signs, especially in the first months: a new headache, more confusion, dizziness, vision changes, nausea, trouble walking, or a seizure.2 Call the prescribing doctor the same day.
Call 911 for stroke-like signs such as sudden weakness on one side, trouble speaking, a face that droops, or a seizure. Tell the emergency team the person takes lecanemab. ARIA can look like a stroke, and some clot-busting stroke drugs could cause dangerous bleeding in a person with ARIA.2
Blood thinners raise the risk of bleeding in the brain. In the trial, 2.5% of people on lecanemab who also took a blood thinner had a large brain bleed. No one on placebo did.2 Make sure every doctor knows about lecanemab. Never stop or change a blood thinner or any medicine on your own. Talk with your doctor or pharmacist first.
For more detail, see our full page on ARIA.
APOE testing: why the gene matters
APOE is a gene everyone has. One form, called e4, raises the risk of Alzheimer's. It also raises the risk of ARIA with lecanemab.2 People get one copy of the gene from each parent, so a person can have zero, one or two copies of e4.
| APOE e4 copies | Any ARIA on lecanemab | Swelling (ARIA-E) with symptoms |
|---|---|---|
| None | 13% (about 1 in 8) | 1% |
| One copy | 19% (about 1 in 5) | 2% |
| Two copies | 45% (almost 1 in 2) | 9% |
Source for the table: FDA label for Leqembi, CLARITY AD data.2
The FDA recommends an APOE test before starting lecanemab.2 The doctor should talk with you about what the result could mean before the test. A person can still be treated without testing, but then no one knows their true risk.2
Gene results can affect your children and siblings too, because they may carry the same gene.6 Some people want genetic counseling first. Read more on genes and dementia.
Cost and Medicare coverage
Prices and rules change often. These facts are current as of October 2026.
The IV form. The makers set a list price of $26,500 a year for the drug alone.5 That price was announced when the drug first came out, so the cost today may be different. Medicare Part B may cover it for early Alzheimer's with confirmed amyloid.7 After the Part B deductible, you usually pay 20% of the Medicare-approved amount. At list price, that could be several thousand dollars a year. MRI scans, PET scans, tests and doctor visits add more.7
The registry rule. Medicare covers these drugs only if your doctor sends data on how you are doing to a CMS-approved study or registry.7,8 The doctor sends data when you start and then every six months for up to two years.8 This rule began in 2022. The CMS page, last updated in March 2026, still lists it.8 Ask whether your doctor or clinic takes part.
The at-home pen. Part B usually covers drugs you would not give yourself, such as those given in a doctor's office.11 Because the pen is used at home, coverage may come through a Part D drug plan instead. Medicare.gov says a Part D plan might cover these drugs when Part B rules are not met.7 In 2026, Part D caps what you pay out of pocket for covered drugs at $2,100 for the year.10 Ask your plan whether it covers Leqembi Iqlik and what you would pay.
Other help:
- Medigap (supplement) plans help pay your share of Original Medicare costs, such as coinsurance. Many pay some or all of the Part B 20%.12
- Medicaid can pay the 20% for people who have both Medicare and Medicaid, or who are in a Medicare Savings Program.5
- Extra Help is a Medicare program that helps pay Part D drug costs for people with limited income.10
- Ask the clinic whether the drug maker has a patient support line or a free-drug program you might qualify for.
See paying for new Alzheimer's drugs for more.
Tips for families
Lecanemab means many visits and scans, especially early on. A few things can help:
- Keep a shared calendar of doses and MRI dates. A memory notebook can hold the medicine list and symptoms to report.
- Carry a card or phone note that says the person takes lecanemab, for emergencies.
- If English is not your first language, ask for a free medical interpreter.
- Plan for the caregiver's own rest. See caregiver burnout.
The Alzheimer's Association 24/7 Helpline at 800-272-3900 can help you find doctors and answer questions about treatment.5
Questions to ask the doctor
Is lecanemab a good fit for us?
- Is the diagnosis Alzheimer's, and is it still in the mild stage?
- How was amyloid confirmed? Do we need a PET scan or spinal fluid test?
- Do any of my health problems or medicines make it unsafe?
- How does it compare with donanemab (Kisunla)?
What are my personal risks?
- Should I have an APOE test? What will the result change?
- What is my risk of ARIA, given my genes and my MRI?
- I take aspirin, a blood thinner or supplements. Is that a problem?
- Who do we call if symptoms appear at night or on a weekend?
How will treatment work for us?
- Should we start with IV infusions or the at-home pen? Can we switch later?
- Who teaches us to use the pen? When are the MRI scans?
- How will we know if it is working? When would we stop?
What will it cost?
- Is your clinic part of a Medicare-approved registry?
- What will we pay for the drug, the infusions or pens, the scans and the visits?
- Does my Part D plan cover the pen? Is there financial help?
Sources
- van Dyck CH, et al. Lecanemab in early Alzheimer's disease. N Engl J Med, 2023. PubMed
- U.S. Food and Drug Administration. LEQEMBI and LEQEMBI IQLIK (lecanemab-irmb) prescribing information, revised July 2026. FDA, 2026. FDA label
- U.S. Food and Drug Administration. FDA converts novel Alzheimer's disease treatment to traditional approval. FDA, 2023. FDA
- Alzheimer's Association. Alzheimer's Association welcomes FDA approval of Leqembi subcutaneous starter dose. Alzheimer's Association, 2026. alz.org
- Alzheimer's Association. Lecanemab (Leqembi). Alzheimer's Association, 2026. alz.org
- Cummings J, et al. Lecanemab: appropriate use recommendations. J Prev Alzheimers Dis, 2023. Springer
- Medicare.gov. Monoclonal antibodies for treating early Alzheimer's disease. Centers for Medicare & Medicaid Services, 2026. Medicare.gov
- Centers for Medicare & Medicaid Services. Coverage with evidence development: monoclonal antibodies directed against amyloid for the treatment of Alzheimer's disease. CMS, 2026. CMS
- U.S. Food and Drug Administration. FDA clears first blood test used in diagnosing Alzheimer's disease. FDA, 2025. FDA
- Medicare.gov. Costs for Medicare drug coverage. Centers for Medicare & Medicaid Services, 2026. Medicare.gov
- Medicare.gov. Prescription drugs (outpatient). Centers for Medicare & Medicaid Services, 2026. Medicare.gov
- Medicare.gov. Medigap (Medicare Supplement Insurance). Centers for Medicare & Medicaid Services, 2026. Medicare.gov
Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.