Aspirin can protect your heart, but only in specific circumstances. For people who have already had a heart attack or stroke, a daily low-dose aspirin is a well-established, guideline-recommended therapy. For people who have never had a cardiovascular event, the picture has shifted dramatically in recent years. Updated guidelines now recommend against starting daily aspirin for most older adults because the bleeding risks outweigh the benefits.
How Aspirin Protects the Heart
Aspirin works by blocking platelets, the tiny blood cells responsible for clotting. Specifically, it stops the production of a chemical called thromboxane A2, which normally signals platelets to clump together. When platelets clump inside a narrowed artery, they can form a clot that blocks blood flow entirely, causing a heart attack or stroke. By keeping platelets from sticking together as easily, aspirin reduces the chance of that clot forming.
This effect kicks in quickly. Platelet aggregation drops within minutes of taking a dose, and because aspirin permanently disables each platelet it touches, a single daily dose is enough to maintain the effect as your body cycles through new platelets over the course of a week.
If You’ve Already Had a Heart Attack or Stroke
For people with established cardiovascular disease, daily aspirin is a cornerstone of treatment. Guidelines recommend 75 to 100 mg daily (the standard low-dose tablet in the U.S. is 81 mg) for secondary prevention, meaning you’re trying to stop a second event after already having one. This applies to people who have had a heart attack, an ischemic stroke, a stent placed in a coronary artery, or bypass surgery.
In this group, the math is straightforward: the risk of another cardiovascular event is high enough that aspirin’s clot-preventing benefits clearly outweigh its bleeding risks. If you’ve been prescribed aspirin after a heart event, stopping it without medical guidance can be dangerous, particularly if you have a stent, where abruptly discontinuing aspirin raises the risk of a clot forming inside the stent.
If You’ve Never Had a Heart Event
This is where recommendations have changed the most. For years, many adults took a daily baby aspirin as a kind of cardiovascular insurance. That thinking has been largely reversed. The U.S. Preventive Services Task Force now recommends against starting low-dose aspirin for heart disease prevention in adults 60 and older. The task force concluded with moderate certainty that for this age group, initiating aspirin has no net benefit.
This was a notable shift from the 2016 guidelines, which had left the door open for adults in their 60s with elevated heart risk to consider aspirin on a case-by-case basis. The updated recommendation closed that door, moving it to a grade D, which means “don’t do this.”
For adults aged 40 to 59 who have a 10% or greater chance of a cardiovascular event in the next 10 years, the decision is more nuanced. The potential benefit exists but is small, and the task force suggests it should be an individual conversation rather than a blanket recommendation. In practice, this means aspirin for primary prevention is now limited to a narrow group of younger, higher-risk adults who also have a low bleeding risk.
The Bleeding Tradeoff
The same property that makes aspirin useful, keeping blood from clotting, is also what makes it risky. Low-dose aspirin increases the risk of major gastrointestinal bleeding by about 58% compared to not taking it. In absolute terms, that translates to roughly 1 to 2 extra major GI bleeding events per 1,000 people per year, depending on your baseline risk. Aspirin also raises the risk of bleeding in the brain (hemorrhagic stroke) by about 27%, though this is less common, adding roughly 0.3 extra events per 1,000 people per year.
These numbers may sound small, but they accumulate over years of daily use. And for someone without existing heart disease, the number of heart attacks aspirin would prevent can be similar in magnitude to the number of serious bleeds it causes. That’s the core reason the guidelines shifted: in lower-risk people, aspirin essentially trades one type of serious event for another.
Bleeding risk rises with age, which is a key reason the recommendation is strongest against starting aspirin after 60. It also increases if you take blood thinners, have a history of stomach ulcers, drink alcohol regularly, or use anti-inflammatory painkillers like ibuprofen or naproxen.
81 mg vs. 325 mg
The standard dose for heart protection is 81 mg, commonly sold as “baby aspirin” or “low-dose aspirin.” Higher doses, up to 325 mg, were once common but are now generally reserved for specific short-term situations, such as the first days after a stent placement. For long-term daily use, 81 mg provides the same platelet-blocking benefit with a lower risk of stomach irritation and bleeding. Clinical trials comparing the two doses for secondary prevention found no meaningful difference in preventing heart attacks or death.
What to Do If You’re Already Taking Daily Aspirin
If you started a daily aspirin years ago for prevention and have never had a heart attack or stroke, the current evidence suggests the benefit may not justify the risk, especially if you’re over 60. That said, stopping aspirin abruptly can carry its own risks in certain situations. This is worth a direct conversation about your individual risk profile rather than a decision to make on your own based on a headline.
If you’re taking aspirin because you’ve had a heart attack, stroke, or stent, the calculus is different. The benefits in your case are well established, and continuing therapy is the standard of care. The recent guideline changes apply to people without a history of cardiovascular disease, not to those already being treated for it.