New research shows taking an aspirin a day to help prevent heart attacks, stroke, and certain cancers is only effective for people under a certain weight.

Do you take aspirin as a way to protect yourself against heart disease and certain types of cancer?

Doing so may not give you all the benefits that were previously found if you’re over a certain weight, a new study claims.

A report in The Lancet finds that the effects of aspirin in preventing cardiovascular events and cancer vary significantly based on weight.

Yet aspirin has shown promise in the past.

A study out last year in Circulation found that stopping low-dose aspirin therapy could increase a person’s risk for experiencing a stroke or heart attack.

Also, a recent study found that long-term aspirin use can significantly lower the incidence of digestive cancers.

Because of findings from studies like these, the U.S. Preventive Services Task Force recommends taking a low-dose aspirin regularly if you’re between the ages of 50 and 69 as a way to prevent heart attacks, strokes, and some types of cancer.

In the latest study, people between 110 and 154 pounds who took an 81 milligram (mg) baby aspirin were found to have about a 23 percent lower risk for heart attack, stroke, or another major cardiovascular event.

But those above 154 pounds didn’t receive the same benefits from taking aspirin.

When researchers considered increasing the dose for people who had higher weights, they noted that the next highest dose is a full dose of aspirin — 325 mg.

The problem with taking 325 mg daily is that it’s been linked to excessive bleeding in some people.

Learning that weight plays a role in the efficacy of aspirin in cancer and cardiovascular event prevention, the authors say that a one-size-fits-all approach to dosing aspirin is likely not optimal.

“Aspirin should be considered for anyone who has already suffered a heart attack or stroke not caused by hemorrhage, as well as middle-aged men and women at increased risk of cardiovascular disease based on heart disease risk factors,” said Dr. Michael Miller, a cardiovascular medicine professor at the University of Maryland School of Medicine.

Cardiovascular event risk factors include family history of premature heart disease, hypertension, diabetes, high cholesterol, and smoking.

However, determining which dose will work in heavier people is still an unknown.

Miller said the researchers didn’t study the effects of a “compromise dose,” which would be half of a 325-mg adult aspirin.

Such a dose may not yield the same positive results for heavier people that a smaller one does for individuals under 154 pounds. It could also increase risks for those who have a higher susceptibility to bleeding.

Nevertheless, based on the results of the new research, Miller said he would certainly consider a full-dose aspirin daily for people who weigh more than 154 pounds and smoke cigarettes, or have diabetes or high cholesterol that’s not optimally treated.

He explains, “This is because of their inherently higher likelihood of blood clot formation, for which a higher aspirin dose is likely to be more protective.”

Miller said that aspirin-eligible men and women should talk to their doctors to determine a dose that’s right for them.