Aspirin is indicated in a narrower set of situations than most people assume. Its strongest, most agreed-upon use is in people who already have heart disease or have had a stroke. For preventing a first heart attack or stroke, recommendations have tightened significantly in recent years, and for adults 60 and older, major guidelines now recommend against starting aspirin for that purpose at all. Beyond cardiovascular use, aspirin has specific roles in pregnancy, Kawasaki disease in children, and acute heart attack emergencies.
Secondary Prevention: After a Heart Attack or Stroke
The clearest indication for daily aspirin is in people who have already had a heart attack, stroke, or been diagnosed with cardiovascular disease. This is called secondary prevention, and it remains the backbone of aspirin’s clinical value. A meta-analysis of 11 randomized trials found that aspirin alone reduced the combined risk of stroke, heart attack, and death from vascular causes by 13% in people who had already experienced a stroke or transient ischemic attack (a “mini-stroke”).
For anyone with established coronary artery disease, a prior heart attack, or a history of ischemic stroke, low-dose aspirin (typically 81 mg per day) is standard long-term therapy. In this group, the benefit of preventing another cardiovascular event clearly outweighs the bleeding risk. If you’ve been prescribed aspirin after a cardiac event or stroke, stopping it without medical guidance can be dangerous.
During a Suspected Heart Attack
Aspirin is one of the first things given during a suspected heart attack, and it’s one of the few interventions bystanders can offer before paramedics arrive. The recommended dose is 162 to 325 mg of non-enteric-coated aspirin, chewed and swallowed rather than swallowed whole. Chewing gets the drug into the bloodstream faster, helping to limit the blood clot that’s blocking the coronary artery. This applies unless the person has a known severe aspirin allergy or aortic dissection is suspected.
Primary Prevention: Before Any Heart Event
This is where guidelines have shifted most dramatically. For decades, many adults took a daily aspirin to prevent a first heart attack. Current recommendations from the U.S. Preventive Services Task Force, updated in 2022, are far more cautious.
For adults aged 40 to 59 with a 10-year cardiovascular risk of 10% or greater (estimated using standard risk calculators that factor in blood pressure, cholesterol, smoking, and diabetes), aspirin is no longer a blanket recommendation. Instead, it’s an individual decision. The net benefit in this group is considered small, and it’s most appropriate for people who are not at increased risk of bleeding and are willing to commit to taking it daily. The standard dose is 81 mg per day.
For adults 60 and older, the Task Force explicitly recommends against starting aspirin for primary prevention. The reasoning is straightforward: bleeding risk rises with age, and the evidence shows that in older adults, the harms of daily aspirin likely outweigh the cardiovascular benefits. The American College of Cardiology, American Heart Association, and American Diabetes Association all echo this caution, recommending against primary prevention aspirin in patients over 70.
What Changed
The previous 2016 guidelines recommended aspirin for a broader population, including for colorectal cancer prevention in adults aged 50 to 59. That cancer prevention recommendation was revoked in 2022 after newer trial data, including the large ASPREE trial, contradicted earlier findings. As it stands, aspirin is no longer recommended specifically for cancer prevention by any major guideline body.
Preeclampsia Prevention in Pregnancy
Low-dose aspirin (81 mg per day) is recommended for pregnant women at high risk of preeclampsia, a dangerous condition involving high blood pressure and organ damage. It should be started between 12 and 28 weeks of gestation, optimally before 16 weeks, and continued daily until delivery.
High-risk factors that trigger this recommendation include a history of preeclampsia, carrying multiples, kidney disease, autoimmune disease, type 1 or type 2 diabetes, and chronic hypertension. Women with more than one moderate risk factor, such as a first pregnancy combined with age 35 or older, a BMI over 30, or a family history of preeclampsia, are also candidates. Both the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine endorse these criteria.
Kawasaki Disease in Children
Kawasaki disease is one of the rare situations where children receive aspirin, and at high doses. Children with this inflammatory condition, which primarily affects blood vessels and can damage the coronary arteries, are treated with high-dose aspirin alongside intravenous immunoglobulin. The aspirin serves as an anti-inflammatory in the acute phase and later, at lower doses, helps prevent blood clots in affected coronary arteries.
Outside of Kawasaki disease (and a few other specific conditions), aspirin is contraindicated in children. The concern is Reye syndrome, a rare but potentially fatal condition involving brain swelling and liver damage. It typically strikes children recovering from a viral illness, particularly influenza or chickenpox, during which aspirin was given. The peak age of onset is 5 to 14 years. Since the 1980s, warnings against giving aspirin to children have been standard in both the U.S. and the U.K.
Bleeding Risk: The Other Side of the Equation
Every aspirin indication involves a trade-off with bleeding. Aspirin works by irreversibly blocking an enzyme involved in platelet clumping, which is why it prevents clots but also makes bleeding harder to stop. Both 81 mg and 325 mg doses produce near-complete suppression of this clotting pathway, which is why the lower dose has become standard for long-term use. There’s no meaningful additional platelet suppression at the higher dose for chronic use.
Data from the ASPREE trial, which followed older adults over a median of 4.7 years, found that aspirin increased overall gastrointestinal bleeding risk by 60% compared to placebo. Upper GI bleeds were nearly twice as common in the aspirin group. While the absolute risk of a serious bleed in any given year remains modest for younger, healthy individuals, it climbs meaningfully with age, concurrent use of blood thinners, history of ulcers, or heavy alcohol use.
This is precisely why the guidelines have narrowed. For someone who has already had a heart attack, a 60% increase in GI bleeding risk is an acceptable price for a meaningful reduction in another cardiac event. For someone who has never had heart disease and is over 60, that same bleeding risk may not be worth the smaller cardiovascular benefit.
When Aspirin Should Be Stopped
If you’re over 60 and taking daily aspirin purely for primary prevention (meaning you’ve never had a heart attack, stroke, or been diagnosed with cardiovascular disease), current guidelines suggest it may be appropriate to stop. Multiple medical organizations now flag aspirin for primary prevention in adults over 70 as a potentially inappropriate medication. Stopping aspirin in this context is generally safe, though it should be done in conversation with a clinician rather than abruptly, especially if you’ve been taking it for years. For anyone taking aspirin for secondary prevention, the calculus is entirely different, and discontinuation carries real risk.