The short answer is: maybe, but with real caution, and only after a doctor weighs your specific bleeding risk. Leqembi and Kisunla — anti-amyloid antibody drugs for early Alzheimer's — both raise the risk of brain bleeding, and blood thinners can make that risk worse. Leqembi (lecanemab) and Kisunla (donanemab) are infusion treatments that clear amyloid plaque in people with mild cognitive impairment or mild-dementia-stage Alzheimer's. Because they can cause bleeding in the brain, combining them with anticoagulants is one of the most important safety conversations a family can have with a prescriber.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What Leqembi and Kisunla are, and why bleeding matters
- What the evidence shows about anticoagulants
- Aspirin is not the same as a full blood thinner
- What expert guidance and the manufacturers say
- Questions to bring to the prescriber
- Frequently Asked Questions
What Leqembi and Kisunla are, and why bleeding matters
Both drugs are monoclonal antibodies given by IV infusion. They target amyloid, a protein that builds up in the Alzheimer's brain. leqembi received full FDA approval on July 6, 2023, and Kisunla followed on July 2, 2024, according to the FDA approval announcement. Both drugs carry a Boxed Warning — the FDA's strongest — for aria, or amyloid-related imaging abnormalities.
ARIA includes brain swelling (ARIA-E) and small brain bleeds (ARIA-H). Per the Leqembi prescribing information, ARIA is often symptom-free but can occasionally be serious, life-threatening, or fatal. Blood thinners matter because they reduce your blood's ability to clot. If a bleed starts in the brain, an anticoagulant can let it grow larger and become harder to stop.
What the evidence shows about anticoagulants
The Leqembi label reports that anticoagulant use was linked to more intracerebral hemorrhages than placebo. In the trial, patients on an anticoagulant — alone or with aspirin — had brain hemorrhage in 2.5% of cases (2 of 79), versus none on placebo, according to the Leqembi label. The label advises caution when considering the drug for anyone on anticoagulants or with other bleed risk factors. Kisunla shows a similar pattern.
Serious brain hemorrhages larger than 1 cm, some fatal, occurred in its trials. The Kisunla label reports large hemorrhages in 0.5% of Kisunla patients versus 0.2% on placebo in one study, and about 1% in another. These are small percentages, but the outcomes can be severe. That is why both labels single out anticoagulation as a high-risk situation rather than a routine one.
Aspirin is not the same as a full blood thinner
Not all "blood thinners" carry the same risk here. It helps to separate two groups: The highest-risk scenario both labels highlight is tPA, a clot-dissolving thrombolytic given for acute stroke, in a patient on these drugs. According to the Kisunla label, the choice is individualized by the prescriber — it is not an automatic yes or no.
- Antiplatelet drugs like aspirin: these were allowed in the trials and are generally managed with caution.
- Full anticoagulants like warfarin and DOACs (for example, apixaban or rivaroxaban): these are the higher-risk category both labels flag.
What expert guidance and the manufacturers say
Expert appropriate-use recommendations go further for Kisunla. Because macrohemorrhage — a large brain bleed — carries high illness and death rates on anticoagulation, one set of appropriate-use recommendations published in Alzheimer's & Dementia advises against donanemab in patients taking anticoagulants.
The manufacturers echo this caution. Eli Lilly notes its Kisunla trials did not enroll patients on therapeutic anticoagulants and advises caution or avoidance, per Lilly's medical information. If a large bleed occurs, dosing must be suspended until an MRI confirms it has stabilized.
Questions to bring to the prescriber
Use these to guide the conversation with the neurologist or care team: The decision rests on your individual profile. A person on aspirin for heart health sits in a very different risk category than someone on warfarin for a mechanical heart valve.
- Which blood thinner is involved — aspirin, or a full anticoagulant like warfarin or a DOAC?
- Why is the blood thinner prescribed, and could the reason change the risk balance?
- Do I have other bleed risk factors, such as prior brain bleeds or certain genetic (APOE4) status?
- What is the MRI monitoring plan for ARIA before and during treatment?
- What happens to the treatment plan if an emergency stroke drug like tPA is ever needed?
Frequently Asked Questions
Can someone on daily aspirin take Leqembi or Kisunla?
Often yes, with caution. Aspirin-only patients were included in the trials, but the prescriber still weighs individual bleed risk before starting.
What about warfarin or DOACs like apixaban?
These full anticoagulants are the higher-risk group. Expert recommendations advise against donanemab in patients on anticoagulants, and Leqembi's label urges strong caution.
Does the treatment stop if a bleed is found?
For a large hemorrhage, dosing is suspended until an MRI confirms it has stabilized, per Eli Lilly's guidance.
