What Your Blood Type Says About Your Health

Knowing your type could give clues about your risk of stroke and heart attack

Hallie Levine,

Updated April 29, 2026

AARP

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Updated April 29, 2026

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Key takeaways

Blood types A and B are linked to higher risks of blood clots, heart attack and stroke.
Type O blood is tied to a slightly lower risk of thrombosis and some heart events.
Experts say lifestyle factors matter far more than blood type for health.

Do you know your blood type? There’s a good chance that you don’t. More Americans know their horoscope sign (66 percent) than their blood type (51 percent), according to a 2023 survey from laboratory company Quest Diagnostics. There are compelling health reasons why you should know.

Types of blood

Blood types are determined by the presence or absence of certain substances, called antigens, that can trigger an immune response if they are foreign to the body.

Blood Type and Your Health

What the research shows:

Types A and B: Higher risk of blood clots, heart attacks and strokes.
Type AB: Higher risk of stroke and inflammation. Those with AB+ blood can accept blood from all donors and are called universal recipients.
Type O: Slightly lower risk of thrombosis, blood clots, heart attacks and strokes. People with type O- blood are universal donors and can donate to anyone.

Note: a healthy lifestyle likely trumps blood type in terms of increasing or decreasing risks.

There are four main blood types: A, B, O and AB, according to the American Red Cross. In addition to these antigens, there’s a protein called the Rh factor, which can either be present (+) or absent (-). That means there are eight blood subtypes: A+, A-, B+, B-, O+, O-, AB+ and AB-.

Blood type and your heart

Research suggests that people with certain blood types — namely A and B — are at higher risk of developing blood clots and having heart attacks and strokes.

“We think about blood type a lot when we think about transfusions,” says Dr. Robert Salazar, a cardiologist at Houston’s Memorial Hermann Health System. There may be some benefits to know about it for heart health, he adds.

“Increasingly, there is a push towards the individualization of medicine and medical advice,” he explains. Adding information about blood type, he says, may help inform doctors on how to best treat patients.

Types A and B and blood clots

People with blood types A and B are at higher risk of developing blood clots, compared with people who have type O blood, according to a 2020 study published in the American Heart Association journal Arteriosclerosis, Thrombosis, and Vascular Biology.

The study, which looked at more than 400,000 people, found that types A and B were 50 percent more likely to develop the blood clots in the legs called deep vein thrombosis and 47 percent more likely to develop a pulmonary embolism — when a clot travels to the lungs — than people with type O blood. They were 8 percent more likely to have a heart attack and 10 percent more likely to experience heart failure than type Os.

There are many possible reasons why this happens, says Dr. Mary Cushman, a hematologist at the University of Vermont Medical Center and a professor of medicine at the Larner College of Medicine at UVM in Burlington, Vermont. “The enzyme that controls blood type has other actions,” Cushman explains. One of these is to modify a protein called the von Willebrand factor, which is very important in forming blood clots.

“The modifications to the protein are different in different blood types,” she says. “So people with type O blood have the lowest levels of von Willebrand factor on average and the lowest risk of abnormal clots. Type AB has the highest level and, in some studies, the highest risk of blood clots.” There may also be some differences in platelets, the small cell fragments in the blood that form clots, says Dr. Joshua Beckman, chief of vascular medicine at the UT Southwestern Medical Center in Dallas. This may make you more susceptible to clotting.

Type A, type AB and cholesterol, stroke

There’s evidence to suggest that type A blood is linked to higher levels of low-density lipoprotein (LDL) cholesterol, the waxy substance that clogs arteries. Type AB blood is linked to inflammation, which may adversely affect blood vessels. Larger studies need to be done before coming to any definite conclusions, Beckman says.

Blood type may affect stroke risk too. A 2022 study published in Neurology reviewed 48 studies of 17,000 stroke patients and found that people with type A were 16 percent more likely to have an early stroke than people with other blood types, and those with type O were 12 percent less likely. An earlier study by Cushman found that those with blood type AB, compared with O, had a 1.8 times higher risk of stroke; other blood types weren’t affected.

Blood type and COVID-19 risk

Scientists are studying how blood type might affect risks from the COVID-19 virus, but they say it’s too early to draw firm conclusions.

One Danish study, published in Immunobiology, found that among hospital workers exposed to COVID-19 from April to September 2020 —when the vaccines weren’t out yet and the workers did not have personal protection — those with type O had a lower risk of getting the virus.

A 2023 report in the journal Blood suggested that the SARS-CoV-2 virus may stick to host cells more often in people with type A blood.

Blood type and other health factors

Research has explored the connection between blood type and health:

People with type O blood have a higher chance of getting seriously ill from cholera, according to a 2016 report in The American Journal of Tropical Medicine and Hygiene.
Type O blood may have some protection from severe malaria, according to a 2019 meta-analysis in the journal Blood Reviews.
A 2024 review in the journal BMC Medicine found that those with positive or negative type B blood had a higher risk for developing diabetes, compared with those who didn't have type B blood.

What you can do

It’s important to keep research findings in context. Though certain blood types could mean an increased chance of health problems such as blood clots and stroke, the risk is relatively small compared with the dangers of other factors like smoking and high blood pressure, and blood type doesn’t tell you much about your personal risk, Cushman points out.

You also shouldn’t let your blood type give you a false sense of security. If you’re having surgery or have cancer — both situations can raise the risk of blood clots — Cushman recommends that you talk to your health care provider about a blood clot prevention plan.

“If you have O blood type, you may have a slightly lower risk of some diseases like thrombosis, but it doesn’t completely protect you from the risk,” she says. Thrombosis occurs when clots block blood vessels.

Knowing your blood type may give you added insight into your heart health, Salazar says. Though doctors often talk about manageable risk factors, such as high blood pressure, diabetes and smoking, there’s less conversation about genes or the genetic risk for heart disease, he says. Having a patient’s blood type is a “way to try to narrow down individuals who may be at high risk,” he adds.

For these people, following the American Heart Association’s Life’s Essential 8 — eating right, staying active, not smoking, getting enough sleep, managing weight, controlling cholesterol, managing blood sugar and managing blood pressure — may be even more important.

Regardless of your blood type, everyone should have a heart-healthy lifestyle, Cushman says.

“Following the guidance of the American Heart Association’s Life’s Essential 8, for example, will add years to your life and reduce your risk of thrombosis-related outcomes like heart attack, stroke and venous thrombosis,” she says.

How to find out your blood type

A simple blood test can reveal your blood type. If you’re curious, you can ask your doctor to have it tested the next time you need blood work. There’s another very quick and easy way to figure out your blood type that’s also altruistic: give blood. A 2019 national survey conducted by the Red Cross found that more than half of people believe they need to know their blood type to do so, but that’s not true.

Once you give blood, you’ll learn your blood type when you receive your donor cord, and you can create a profile through the Red Cross Blood Donor app. Slightly more than a third — 37 percent — of the world’s population has the most frequently occurring blood type, O+.

Editor's note: This article, originally published February 21, 2023, has been updated with new information.

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The key takeaways were created with the assistance of generative AI. An AARP editor reviewed and refined the content for accuracy and clarity.

Hallie Levine is a contributing writer and an award-winning medical and health reporter. Her work has appeared in The New York Times, Consumer Reports, Real Simple, Health and Time, among other publications.