Low-dose aspirin is recommended in two clear situations: after a cardiovascular event like a heart attack or stroke, and in select adults aged 40 to 59 whose 10-year risk of heart disease is 10% or higher. A third use applies to pregnant people at high risk for preeclampsia. Outside these groups, the benefits of daily aspirin generally don’t outweigh the bleeding risks, and current guidelines specifically recommend against starting it if you’re 60 or older and have never had a heart attack or stroke.
After a Heart Attack, Stroke, or Heart Procedure
The strongest case for daily low-dose aspirin is in people who already have cardiovascular disease. If you’ve had a heart attack, a stroke, coronary artery bypass surgery, or a stent placed, guidelines recommend 75 to 100 mg of aspirin daily for ongoing protection. In the United States, the standard tablet is 81 mg; in the UK, it’s 75 mg. Both fall within the effective range.
This is called secondary prevention, meaning you’re trying to stop a second event. Aspirin works by permanently disabling an enzyme in platelets that promotes clotting. Because platelets can’t repair themselves, each one affected by aspirin stays inactive for the rest of its lifespan, roughly 7 to 10 days. Your body continuously makes new platelets, so daily dosing keeps a large proportion of them unable to form dangerous clots. For people with established heart disease, this effect meaningfully reduces the chance of another heart attack or stroke, and the benefit clearly outweighs the bleeding risk.
Primary Prevention: Ages 40 to 59
Primary prevention means taking aspirin before you’ve ever had a cardiovascular event, purely to lower the odds of having one. The U.S. Preventive Services Task Force updated its guidance in 2022 and narrowed the window significantly compared to older recommendations. The task force now says aspirin for primary prevention should only be considered in adults aged 40 to 59 whose estimated 10-year cardiovascular risk is 10% or greater. Even then, the net benefit is described as small, and the decision should be individualized.
Your 10-year cardiovascular risk is calculated using factors like age, blood pressure, cholesterol levels, smoking status, and diabetes. Free online calculators (sometimes called ASCVD risk calculators) can estimate this number using results from a routine blood panel. If your risk falls below 10%, aspirin for prevention is unlikely to help enough to justify the downsides. If it’s 10% or higher, the conversation shifts to whether you’re also at increased risk for bleeding, which could tip the balance back against aspirin.
Why Guidelines Say No After Age 60
The task force explicitly recommends against starting aspirin for primary prevention in adults 60 and older. The reason is straightforward: bleeding risk rises with age while the cardiovascular benefit stays roughly the same. In women over 60, for example, the rate of gastrointestinal bleeding is about three times higher than in younger women (roughly 2 per 1,000 people per year compared to 0.6 per 1,000). That elevated bleeding risk erodes the protective benefit of aspirin to the point where starting it fresh no longer makes sense.
This doesn’t mean you should stop aspirin if you’re over 60 and already taking it for an established heart condition. The recommendation against initiation applies to people without a prior heart attack, stroke, or related diagnosis. If you’re already on aspirin for secondary prevention, stopping it is a separate decision that depends on your individual history.
Preeclampsia Prevention During Pregnancy
Low-dose aspirin has a distinct role in pregnancy. The USPSTF recommends 81 mg daily for pregnant people at high risk for preeclampsia, starting after 12 weeks of gestation. The American College of Obstetricians and Gynecologists specifies that it should ideally begin before 16 weeks and continue until delivery. Risk factors for preeclampsia include a history of the condition in a prior pregnancy, chronic high blood pressure, kidney disease, autoimmune conditions, and carrying multiples.
Bleeding Risks Worth Knowing
The primary downside of daily aspirin is bleeding. Because aspirin impairs clotting throughout your entire bloodstream, it increases the risk of gastrointestinal bleeds and, more rarely, bleeding in the brain. Several factors raise your baseline bleeding risk further: being over 60, having a history of stomach ulcers, using other anti-inflammatory painkillers like ibuprofen or naproxen, higher body weight, and having diabetes or high blood pressure. The more of these that apply to you, the less favorable the risk-benefit math becomes for preventive aspirin use.
People with a prior history of gastrointestinal bleeding are generally not good candidates for daily aspirin unless the cardiovascular need is compelling enough to justify the added risk.
Best Time of Day to Take It
If you’re taking daily aspirin, some evidence suggests bedtime dosing has advantages. Research shows that aspirin’s effect on platelet activity is weaker during morning hours, and a relevant trial found that taking aspirin at night produced a more significant reduction in platelet clumping. Bedtime dosing also appears to have a modest effect on lowering blood pressure, which peaks in the early morning hours when heart attacks and strokes are most common. That said, the most important thing is consistency. Taking aspirin at the same time every day matters more than picking the perfect hour.
With Food or Without
You’ve probably heard that aspirin should be taken with food to protect your stomach. The advice is widespread, but a systematic review in the British Journal of Clinical Pharmacology found no actual evidence that taking aspirin with food reduces gastrointestinal side effects. What food does do is slow absorption: peak blood levels of aspirin take about 50% longer to reach when you eat beforehand, and the peak concentration drops by roughly 15%. The total amount absorbed stays the same either way.
For daily low-dose aspirin taken as ongoing prevention rather than acute pain relief, this delay in absorption is unlikely to matter. If you find that aspirin on an empty stomach causes discomfort, taking it with a meal is a reasonable choice for comfort, just not one backed by strong evidence of stomach protection. Enteric-coated tablets, which dissolve in the intestine rather than the stomach, are another common option, though their protective benefit is also debated.