Harvard Heart Letter

Ask the doctor: Should I double up on aspirin if I think I am having a heart attack?

Q. I've heard you should take an aspirin if you think you are having a heart attack. I already take aspirin (325 mg) every day. Should I still take an aspirin if I feel a heart attack coming on?

A. You are absolutely right — it is beneficial to chew on an aspirin tablet if you are having a heart attack. In fact, 911 dispatchers often tell people to do this while they are waiting for the ambulance to arrive.

Most heart attacks are caused by blood clots. Aspirin prevents platelets in the bloodstream from clumping, an important stage in clot formation. Although aspirin isn't strong enough to break up a clot that has already formed, many people with heart attacks have clots that are forming, dissolving, and then forming again.

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