Is Aspirin a Good Blood Thinner for Preventing a Heart Attack and Stroke?

An aspirin a day may seem like a simple way to prevent a heart attack and stroke. But — as it turns out — the regular use of aspirin may not be good for everyone. For some, a healthcare professional might recommend a daily, low-dose aspirin if you already have heart disease, have had a stroke, or you’re at high risk for these conditions. But keep in mind, aspirin also comes with risks of serious side effects, like bleeding.

So, should you be taking a daily aspirin? Here’s how to weigh the risks and benefits (but you’ll also need to talk with your primary care provider first).

Is aspirin a blood thinner?

Aspirin works as a blood thinner. Medications that are called blood thinners work to prevent blood clotting and help the blood flow more smoothly. Blood clots are a normal part of the healing process. But if clotting happens when it shouldn’t, it can have serious results. Heart attacks and strokes are two medical emergencies that unnecessary clotting can cause.

So how does aspirin thin blood? Aspirin is an antiplatelet medication. This means that aspirin blocks blood cell fragments, called platelets, from clumping together and forming blood clots. This is how aspirin prevents heart attacks and strokes.

Is aspirin an anticoagulant?

Aspirin is not an anticoagulant. Anticoagulants slow down factors in the blood from starting the clot formation. Anticoagulants like warfarin (Coumadin) and heparin are considered blood thinners, but they work on the clotting factors instead of the platelets.

Both types of blood thinners help prevent clots from forming. They can keep clots from getting bigger, too. But blood thinners don’t break up clots once they’ve formed.

Promotion disclosure

Aspirin

Avg retail price

$9.79(Save 71.40%)

GoodRx discount

$2.80

See all discounts

How it works

Use GoodRx to find medications, pharmacies, and discounts.

GoodRx discounts can help you pay less for your prescription.

Bring your free coupon or savings card to the pharmacy.

How much aspirin does it take to thin your blood?

The dose of aspirin used to thin blood is much lower than the dose used to treat fever, aches, and pains. The usual dose to thin your blood is 81 mg per day. But you should talk with a healthcare professional before starting daily aspirin. Even at low doses, some people are at risk of serious bleeding from aspirin.

How long does it take for aspirin to work?

Aspirin is digested and absorbed quickly into the blood and starts acting on platelets right away. Platelets stop clumping within 60 minutes of taking aspirin. Platelets can’t easily recover their ability to clot once they encounter aspirin. It takes about 10 days after your last dose of aspirin before clotting returns to normal.

Benefits of aspirin

Aspirin, also known as acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug (NSAID). It has several uses and benefits including:

• Lowering fevers 

• Relieving pain 

• Lowering inflammation 

• Preventing cardiovascular disease, such as strokes and heart attacks 

• Treating heart attacks and strokes

• Maintaining heart health after stent placement or coronary artery bypass surgery

The benefits of aspirin, especially in preventing and treating heart disease, have been proven by a large body of research. But as mentioned, aspirin has serious risks — more on this below.

Side effects and risks of aspirin

Although aspirin is available over the counter, it can have serious side effects — especially in people with certain medical conditions. Risks of aspirin include:

• Bleeding in the gut, especially in people who have a history of stomach or intestinal ulcers

• Bleeding in the brain, which is more likely in people with high blood pressure, or aneurysms or tumors in the brain

• Allergic reactions in people who have had allergies or intolerances to aspirin in the past

Who is at higher risk of having side effects with aspirin? People who:

• Have a history of peptic ulcers

• Are older than 65

• Have severe liver or kidney disease

• Drink alcohol heavily

• Have bleeding or clotting disorders

• Take other NSAIDs or blood thinning medications

• Some people with nasal polyps and asthma

Not sure what your risk of taking aspirin might be? Online tools are available to help get you started. But remember, nothing can replace a discussion with a healthcare professional to decide if aspirin is necessary and safe for you. 

Who should take daily aspirin?

The latest research and updates on aspirin seem like they’re always changing. It can be pretty confusing to figure out if you should or shouldn’t be taking aspirin on a regular basis. We’ve broken it down for you below.

Based on the latest recommendations from the U.S. Preventive Services Task Force, the two main groups of people who should take daily low-dose aspirin to prevent cardiovascular disease are:

• People of any age who have already had a heart attack or stroke

• People ages 40 to 59 who are at high risk of cardiovascular disease and have a low risk of bleeding. If you’re in this group, starting low-dose aspirin is a decision that requires a discussion with a healthcare professional.

There may be other reasons you might take a daily aspirin — such as if you’ve had a heart stent placed or are pregnant and at risk for preeclampsia. Always talk with your healthcare professional before starting aspirin.

How much aspirin can you take a day?

The most common doses of daily aspirin are 81 mg and 325 mg tablets taken by mouth per day.  The dose that’s best for you will largely depend on your health history. Your healthcare professional can give you the best guidance on how much to take.

Aspirin 81 mg uses

Low-dose aspirin (81 mg) has been shown to be effective in preventing several medical conditions. One study showed that in people who were already diagnosed with heart disease, both aspirin doses worked equally well to protect heart health. 

Evidence shows that 81 mg aspirin may be useful in preventing:

• Heart attack 

• Stroke

• Preeclampsia  

• Colorectal cancer 

You should talk with a healthcare professional before using aspirin for any of these conditions. And you should never use aspirin for children unless specifically advised by your child’s doctor.

Can you take aspirin with other blood thinners?

In some cases, you can take aspirin with other blood thinners. But this is done strictly under a healthcare professional’s supervision and with caution. NSAIDs such as aspirin are known to interact with blood thinners. However, sometimes it’s medically necessary. 

For example, a person with atrial fibrillation (a type of irregular heartbeat) who is on an anticoagulant needs to take aspirin after a heart attack.

Examples of medicines that can interact with aspirin include:

• Anticoagulants, like warfarin (Coumadin, Jantoven), apixaban (Eliquis), rivaroxaban (Xarelto), and lovenox (Enoxaparin) 

• Antiplatelets, like clopidogrel (Plavix), prasugrel (Effient), and ticagrelor (Brilinta)

• Other medicines, like aspirin and dipyridamole (Aggrenox)

The risk of combining aspirin with blood thinners is significant — and in many cases, is not necessary. In one study, more than 30% of people taking aspirin along with an anticoagulant didn’t have a clear need for aspirin. That’s why it’s so important to ask your healthcare team to see if you should be taking aspirin — especially if you are on other blood thinners.

Why trust our experts?

Written by:

Frank Schwalbe, MD

Frank Schwalbe, MD, is an assistant professor of anesthesiology at the Yale School of Medicine. He has practiced anesthesiology for 30 years.

Edited by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

Our editorial standards

Meet our experts