If you fit in the category of “secondary prevention,” it means that you’ve already had a heart attack or stroke, or you have underlying heart or vascular disease or diabetes. In these cases, the upside of taking aspirin likely outweighs the downside. That said, you still need to speak with your doctor in case you have other complications, such as an allergy to aspirin, a bleeding or clotting disorder, or a history of gastrointestinal bleeding.