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Q: I am thinking about taking a baby aspirin every day to prevent a heart attack or stroke. But it seems the recommendations keep changing. How do you decide?

A: Taking a daily aspirin isn't something you should decide to do on your own. While it may sound like a good idea, there are risks to taking even low dose aspirin. So talk it over with your doctor before you start.

Everyone's blood has a tendency to form clots. We need clots to stop any bleeding that may start, such as from a cut or a stomach ulcer. On the other hand, if clots form too easily, they can plug up an artery, causing a heart attack or the most common kind of stroke. Aspirin works to lower the risk of heart attack and stroke because it reduces the tendency of blood to clot. But that means aspirin also increases the tendency to bleed.

Aspirin therapy is typically prescribed to people who have had a heart attack or stroke. Other candidates for anti-clotting therapy include people who've had coronary artery bypass surgery, people who've had a stent implanted to keep an artery open, and people with peripheral artery disease (significant plaque buildup in the leg arteries).

As a purely preventive therapy, who should take aspirin and at what dose is hotly debated. The more cardiovascular risk factors you have, the more likely you will benefit from taking aspirin. Those risk factors include diabetes, smoking, high blood pressure, a high LDL cholesterol, a family history of heart disease, obesity and physical inactivity.

But there are risks, even with low-dose aspirin. Since aspirin reduces the blood's ability to form clots, it also increases the risk of bleeding. The most common form of serious bleeding is from the stomach or upper intestine. Rarely, bleeding into the brain can occur, which may result in disability or death. That is why you should discuss whether to be on aspirin therapy with your doctor and not just start taking it.

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Although most doctors recommend a "baby" aspirin (81 milligrams), whether that is the best dose for prevention is debated. Also undetermined is whether it's best to take an aspirin with a safety coating (called an enteric coating), in order to reduce the risk of stomach bleeding. Some data suggest the coating may interfere with the body's ability to absorb the aspirin. For people who do take aspirin, I suggest the uncoated form taken with food.

In preparation for your aspirin discussion with your doctor, check out the aspirin risk calculator at

(Howard LeWine, M.D., is an internist at Brigham and Women's Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit


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