You’ve probably heard that taking one baby aspirin every day can significantly reduce your risk of getting a heart attack or stroke.

Researchers at the University of North Carolina found that regular aspirin consumption cut the risk of coronary heart disease by 28 percent in people who’d never had a heart attack or stroke, but were at heightened risk.

You may have also heard that the FDA isn’t so sure that aspirin is delivering as advertised. Last year, the organization released a statement, announcing that they had “reviewed the available data and does not believe the evidence supports the general use of aspirin for primary prevention of a heart attack or stroke.”

So which is it? Should you be taking an aspirin or not? Is it helping you, or is it just a placebo?

It may depend on whether your blood pump is actually in peril.

“Low dose aspirin reduces cardiovascular events in subjects with known cardiovascular or cerebrovascular disease,” says Dr. Prediman K. Shah , M.D., the director of the Oppenheimer Atherosclerosis Research Center, as well as a professor of medicine at Cedars Sinai and UCLA.

In other words, if you have heart disease or have already suffered a heart attack or stroke, low-dose aspirin can be cheap artery insurance.

And there’s research to back this up. A 2009 meta-analysis in The Lancet concluded that patients who popped a low dose of aspirin every day had a nearly 20 percent lower chance of having a second stroke or heart attack than those who didn’t follow an aspirin regimen.

What counts as low dose? Right around 81 mg, which is the equivalent of what used to be called baby aspirin, instead of the 325 mg in a regular-strength tablet.

But what if your heart is perfectly healthy? Dr. Shah says you may want to reconsider that aspirin habit.

“Its value in healthy subjects without known cardiovascular or cerebrovascular disease is less certain,” he says. So it may be helping, but there’s no conclusive evidence either way.

There is, however, evidence that it may be hurting. A study in the Journal of the American Medical Association found that aspirin’s blood-thinning properties can increase the risk of stomach or brain bleeding by 55 percent.

“If the risk of having a cardiovascular event is low, then the risk of bleeding will likely offset any beneficial effect of aspirin,” said Dr. Antonio Nicolucci, M.D., one of the study’s authors.

But the beneficial effects may not be limited to your heart. Dr. Shah points out that “some otherwise healthy individuals may have a net benefit if they are known by imaging tests to have extensive clinically silent subclinical atherosclerosis or diabetes.”

Confused yet? Don’t be. The short answer is, there’s no across-the-board correct rule about aspirin and heart health that applies to everybody.

A good place to begin—according Dr. Ravi Hira, M.D., a cardiology fellow at Baylor College of Medicine—is with the Framingham Risk Calculator, a tool that predicts your chance of having a heart attack in the next decade.

Go to cvdrisk.nhlbi.nih.gov and enter your age, total and HDL cholesterol numbers, and systolic blood pressure. You can do it from home or even your smart phone, as long as you know your current stats.

If your 10-year risk is higher than 6 percent, ask your doctor about making aspirin your ally, says Dr. Hira. But if your risk is 6 percent or lower, keep the cap on the bottle—the benefits of daily aspirin don’t outweigh the dangers.