Can Aspirin Reduce the Risk of a Stroke?

It is recommended for certain conditions

Aspirin is a medication that has many benefits—it reduces fever, diminishes pain, has anti-inflammatory properties, and has antiplatelet properties that prevent blood clots.

Due to its antiplatelet and anti-inflammatory effects, daily aspirin may be recommended if you have had an ischemic stroke. Used in this way, aspirin can lower your risk of having another stroke. A stroke is a type of brain damage that occurs when blood flow in a region of the brain is interrupted, usually due to a blood clot. 

When taken as recommended, daily aspirin has been shown to reduce the risk of stroke and death from stroke, as well as risk of recurrent stroke by 1.1%–3.6%.

This article will discuss how aspirin may help reduce the risk of a recurrent stroke, benefits, risks, who shouldn't take aspirin, and dosage.

Daily aspirin is siometimes recommended to prevent a stroke

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How Does Aspirin Prevent a Stroke? 

Platelets are cells that are active in producing blood clots. Aspirin prevents blood clots by preventing platelets from sticking together. It also acts as an anti-inflammatory medication.

Inflammation is the body's response to injury or infection that results in swelling and activation of immune system cells. Inflammation is a factor in blood vessel disease that contributes to a stroke.

When it’s taken every day, aspirin can help prevent a recurrent stroke for some people who are at risk of having an ischemic stroke, which is a stroke caused by a blockage of blood flow to the brain. 


While blood clots are important to prevent excess bleeding from wounds, they can be dangerous if they form in the brain, the heart, the lungs, and other regions of the body. Aspirin can help prevent platelets from forming clots.

An ischemic stroke occurs when blood flow in an artery in the brain is blocked. Certain conditions predispose you to blood clots in the brain.

Long-term hypertension (high blood pressure), diabetes, inflammation, and unhealthy cholesterol levels lead to atherosclerotic plaques in the heart, carotid arteries, and the brain. The plaques contain cholesterol and other material that can block blood flow in the heart (causing a heart attack) or the brain (causing a stroke).

An ischemic stroke can occur if an atherosclerotic plaque ruptures and travels from the heart or from the carotid arteries and lodges in the brain. An ischemic stroke can also occur if a blood clot forms in an artery within the brain, interrupting blood flow.

Additionally, an irregular heart rhythm, such as atrial fibrillation, can increase the risk of blood clots starting in the heart that may cause a stroke.

Aspirin can prevent these blood clots from forming and may also reduce atherosclerosis. This can help prevent both heart attacks and ischemic strokes.

Aspirin to Prevent Secondary Strokes

Aspirin can reduce the risk of secondary stroke in some people, but you should not take it for primary stroke prevention if you have not had a stroke, unless you are specifically advised to do so by your healthcare provider.


Aspirin is safe for most people, but it has some side effects and risks. 

Common side effects of aspirin are: 

  • Upset stomach 
  • Increased risk of bruising
  • Prolonged bleeding from wounds 
  • Ringing in the ears 
  • Impaired healing of an injury or a wound 

These side effects are not usually considered dangerous, but you should tell your healthcare provider if you experience any of them. 

Serious and uncommon side effects:

Get medical attention promptly if you experience any of these severe side effects while taking aspirin. 

Who Should Not Take Aspirin?

Sometimes aspirin is contraindicated due to underlying medical conditions. If you have ever had an allergic or serious reaction to aspirin, you should not take aspirin for stroke prevention or any other reason. This includes not taking any medication that contains aspirin (such as over-the-counter Excedrin). 

If you are having a planned surgical procedure, your doctor may recommend that you discontinue aspirin for a specified amount of time before your procedure.

Aspirin is not recommended for:

  • Children, due to the potential for a dangerous reaction called Reye’s syndrome 
  • People who have severe bleeding disorders 
  • Anyone who has glucose 6 phosphate dehydrogenase (G6PD) deficiency (a genetic condition that results in the breakdown of red blood cells)
  • People who have a bleeding risk, such as a brain aneurysm (a bulging area in the wall of an artery in the brain)

There may be other situations when aspirin is contraindicated. It is important that you are sure that aspirin is safe for you to use before you start taking it. Tell your doctor and pharmacist about all of your medical conditions and every medication and supplement you are taking.

If you are diagnosed with a new medical condition or are prescribed a new medication while you are already taking aspirin, inform your doctor and pharmacist.


If you are advised to use daily aspirin for stroke prevention, your healthcare provider will recommend a specific daily dose for you that is based on your age, weight, stroke risk, bleeding risk, other medications you take and, and other underlining medical conditions that you have. 

Examples of daily aspirin doses for stroke prevention include 81 milligrams (mg) after an acute ischemic stroke, 81 mg per day for stroke prevention for people who have atrial fibrillation, and possibly 325 mg per day for stroke prevention for people who have carotid artery disease.

Other Blood Thinners 

Aspirin has an antiplatelet effect, and there are other medications described as blood thinners that have antiplatelet activity or have other ways of preventing blood clots. In some situations, aspirin is recommended along with another blood thinners for stroke prevention.

When to Take Aspirin After a Stroke 

Aspirin is not safe for use during an acute stroke. It is used for preventing a recurrent ischemic stroke. It is not considered useful for preventing a hemorrhagic stroke (a stroke caused by bleeding in the brain). 

Aspirin is sometimes used shortly after a stroke is diagnosed if the stroke is ischemic and there is not a substantial risk of bleeding. Sometimes it is not clear whether a stroke is ischemic or hemorrhagic until diagnostic tests are done.

It is not considered safe to use aspirin if there is a risk that symptoms are caused by a hemorrhagic stroke.

Do Not Take Aspirin During a Stroke

You should not take aspirin during an acute stroke or if you aren’t sure whether you are having a stroke. If there is any chance that you could be having a stroke, get immediate medical attention.


Daily aspirin is commonly used for secondary stroke prevention. It can be used to prevent a recurrent stroke for some people who have already had a stroke. This medication prevents blood clots, and it is also an anti-inflammatory drug.

Aspirin can cause some side effects, most of which are mild. But there is a small risk of severe side effects with aspirin. You should not use this medication if it has ever caused you to have an allergic reaction, and sometimes it is contraindicated for people who have a bleeding risk.

A Word From Verywell 

Stroke prevention is important if you have any stroke risk factors. If you have already had a stroke, your doctors will assess your risk factors and recommend preventive measures to lower your risk of having another stroke.

Aspirin is recommended as a preventive measure for some people who have already had a stroke. If your healthcare provider recommends aspirin for you, be sure to take it as directed and report any side effects. Get urgent medical attention if you experience stroke symptoms. 

Frequently Asked Questions

  • Can aspirin make a stroke worse?

    Sometimes aspirin can worsen a stroke by causing increased bleeding if a stroke is already hemorrhagic, and aspirin may cause bleeding in the brain during an ischemic stroke. This complication can worsen symptoms and it can worsen the overall outcome of a stroke.

  • Should I take aspirin if I think I’m having a stroke?

    No, it is not recommended that you take aspirin during a stroke. Aspirin can be beneficial for stroke prevention, and sometimes doctors recommend starting aspirin a few days after a stroke, but bleeding risk has to be established first. 

  • How much aspirin can you take per day?

    It depends on your doctor’s recommendations for you. Factors that determine your dose include other medications that you are taking, any medical conditions you have, your weight, and your stroke risk factors. A typical adult dose for stroke prevention may range between 81 and 325 mg per day, depending on your situation.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.