Is It Safe to Take Low-Dose Aspirin Daily?

Daily low-dose aspirin is safe and beneficial for people who have already had a heart attack or stroke, but for most healthy people trying to prevent a first cardiovascular event, the risks now appear to outweigh the benefits. That distinction is the single most important thing to understand about this topic. Guidelines have shifted dramatically in recent years, and millions of people who were once told to take a daily baby aspirin may no longer need it.

How Low-Dose Aspirin Works in Your Body

Aspirin blocks an enzyme in platelets that produces thromboxane A2, a chemical signal that makes platelets clump together and form clots. Even very small doses are effective at this job. In one study, just 40 milligrams per day reduced thromboxane production by about 85%, and doses of 80 to 160 milligrams pushed that inhibition above 95%.¹² What makes low doses appealing is that they mostly leave prostacyclin alone, a protective substance produced by blood vessel walls that prevents clotting and relaxes arteries. Higher doses tend to suppress prostacyclin too, which partly defeats the purpose.¹

This is why “low-dose” aspirin, usually 75 to 100 milligrams daily, became the standard for cardiovascular protection. It does a good job of keeping platelets from forming dangerous clots while minimizing the suppression of your body’s natural anti-clotting mechanisms.

When Daily Aspirin Is Clearly Worthwhile

If you have already had a heart attack, stroke, or been diagnosed with cardiovascular disease, daily low-dose aspirin remains a cornerstone of treatment. This is called secondary prevention, and the evidence behind it is strong and long-standing. Aspirin’s role in reducing the chance of a second event has been demonstrated in numerous trials and forms the basis of every major cardiology guideline.³ For these patients, the benefit of preventing another heart attack or stroke far outweighs the bleeding risk that aspirin carries.

One important caveat for anyone already taking daily aspirin for cardiovascular protection: stopping abruptly can be dangerous. A large Swedish study found that patients who discontinued aspirin had a 37% higher rate of cardiovascular events compared with those who kept taking it, and the risk climbed shortly after stopping.⁴ A UK study confirmed the pattern, estimating roughly four additional heart attacks per 1,000 patients per year among those who stopped aspirin compared with those who continued.⁵ If your doctor prescribed aspirin for secondary prevention, do not stop it on your own.

Why Most Healthy People Should Skip It

For decades, doctors routinely recommended daily aspirin to healthy people at moderate risk for heart disease. That era is over. Three large trials reported in 2018 collectively changed the conversation. The ASPREE trial in healthy older adults found that aspirin did not extend disability-free survival and increased the risk of major hemorrhage. The ASCEND trial in people with diabetes found that aspirin reduced serious vascular events but increased major bleeding by a similar margin. And the ARRIVE trial in people with multiple cardiovascular risk factors found no benefit for major events but more gastrointestinal bleeding.⁶

A meta-analysis that pooled data from these and earlier trials spelled out the trade-off plainly. In healthy people and those with risk factors, aspirin reduced nonfatal heart attacks by about 21% but had no effect on cardiovascular death and increased major bleeding by 48%.⁷ In other words, for every heart attack aspirin prevented, it caused a serious bleed somewhere else in the body. For most people without existing cardiovascular disease, that is not a favorable trade.

What the Current Guidelines Actually Recommend

The 2022 U.S. Preventive Services Task Force recommendation reflects this shift. For adults aged 40 to 59 with a 10% or greater 10-year cardiovascular risk, the decision to start aspirin should be made on a case-by-case basis between the patient and their doctor, and only for people not at increased risk of bleeding.⁸ For adults 60 and older, the recommendation is against starting aspirin for primary prevention entirely.⁹ This was a notable change from 2016, when the task force had recommended aspirin for adults 50 to 59 at elevated risk and left the door open for those 60 to 69.¹⁰

Despite these guideline changes, self-prescribed aspirin use remains common. A cross-sectional study of moderate-risk individuals found that many people continue taking daily aspirin without medical guidance, driven by outdated advice or the widespread belief that a baby aspirin is harmless.¹¹ If you started aspirin on your own for prevention, this is worth revisiting with your doctor.

The Bleeding Risks in Detail

The main harm from daily aspirin is bleeding, and it shows up in two major places: the gastrointestinal tract and the brain. In cardiovascular prevention studies, even very low doses of aspirin (100 milligrams or less) increased the risk of major gastrointestinal bleeding by about 58%.¹² In absolute terms, that translates to roughly one to two extra major GI bleeds per 1,000 people per year, but the risk climbs for older adults, men, and people with other risk factors for bleeding.¹² The risk is also proportionally higher in people taking aspirin for primary prevention than for secondary prevention, likely because the latter group is under closer medical supervision and getting more protective co-therapies.¹³

In the brain, a meta-analysis of trials involving people without symptomatic cardiovascular disease found that low-dose aspirin was associated with about two extra intracranial hemorrhages per 1,000 people over the study periods. The strongest signal was for subdural hemorrhages, where aspirin raised the risk by roughly 53%.¹⁴ A secondary analysis of the ASPREE trial in healthy older adults found a numerically higher rate of hemorrhagic stroke with aspirin than with placebo, though the difference was not statistically significant.¹⁵

Why Enteric Coating Does Not Solve the Problem

Many people assume that enteric-coated aspirin protects the stomach, but the evidence suggests otherwise. A systematic review found that enteric-coated aspirin was not an effective strategy for GI protection, and even short-term use of low-dose enteric-coated aspirin was associated with measurable small bowel injury.¹⁶ The reason is that aspirin’s effect on the stomach lining is mainly systemic, not local. Even when the pill dissolves in the intestine instead of the stomach, the drug enters the bloodstream and suppresses protective prostaglandins throughout the GI tract.

Proton pump inhibitors like omeprazole do reduce upper GI bleeding when taken alongside aspirin, and a trial showed they cut GI events regardless of aspirin dose.¹⁷ But PPIs do not protect the lower GI tract, and some research suggests they may actually increase small bowel injury from aspirin and raise the risk of lower GI bleeding.¹⁸ So while a PPI can help if you’re at high risk for stomach ulcers and genuinely need aspirin, it is not a blanket solution to aspirin’s GI harms.

Why Age Changes the Equation

The ASPREE trial is the single most influential study behind the guideline changes for older adults. It enrolled over 19,000 healthy people aged 70 and older (65 and older for Black and Hispanic participants in the U.S.) and randomized them to 100 milligrams of aspirin daily or placebo. Aspirin had no effect on disability-free survival and significantly increased the risk of major hemorrhage.¹⁹ What surprised researchers most was that a numerically higher rate of death from any cause was observed with aspirin, driven partly by an unexpected increase in cancer-related deaths.¹⁹ Extended follow-up confirmed these findings: aspirin did not significantly reduce cardiovascular events over a median follow-up approaching five years, and the increased hemorrhage and cancer death signals persisted.²⁰

The biological reason is straightforward. As you age, blood vessels become more fragile, liver and kidney function changes how quickly you clear drugs, and the risk of GI ulceration goes up. All of this tips the balance toward harm. The ASPREE results are the main reason the USPSTF now recommends against starting aspirin for primary prevention in adults 60 and older.

Aspirin and Diabetes

People with diabetes are at higher cardiovascular risk, which makes aspirin seem like a natural fit. The reality is more complicated. The ASCEND trial, the largest trial of aspirin in diabetics without existing vascular disease, followed over 15,000 participants for an average of 7.4 years. Aspirin reduced serious vascular events modestly (about 12% lower risk) but increased major bleeding by 29%, with most of the excess being gastrointestinal.²¹ A Japanese trial with 10-year follow-up found no cardiovascular benefit at all from low-dose aspirin in people with type 2 diabetes, while gastrointestinal bleeding was more than twice as common in the aspirin group.²²

An updated meta-analysis pooling multiple trials did find a modest reduction in major cardiovascular events with aspirin in diabetes, but you would need to treat about 95 people for five years to prevent a single event.²³ The broader meta-analysis that looked across all populations found no benefit of aspirin for nonfatal heart attacks or cardiovascular death specifically among people with diabetes.⁷ For most diabetics without established cardiovascular disease, the evidence does not support routine aspirin use, though individual circumstances can tip the balance.

Low-Dose Aspirin in Pregnancy

One context where low-dose aspirin is actively recommended for certain people is pregnancy. For women at high risk of preeclampsia, starting low-dose aspirin early in pregnancy can reduce the chance of developing the condition. A meta-analysis found that low-dose aspirin lowered preeclampsia risk by about 29% and severe preeclampsia by over 60%, and also reduced the risk of preterm birth and fetal growth restriction.²⁴ Timing matters: aspirin is more effective when started before 16 weeks of gestation.²⁴

There has been debate about whether higher doses work better. A large Scandinavian registry study comparing 150-160 milligrams with 75 milligrams found no significant difference in preeclampsia rates between the two dose ranges.²⁵ Efficacy also varies across populations: some subgroups, particularly non-Hispanic white women, appear to benefit more, while broader populations show less consistent results, likely influenced by factors like aspirin resistance and ethnic variation in response.²⁶ If your obstetrician recommends aspirin for preeclampsia prevention, the safety profile is well established at low doses in pregnancy.

How Ibuprofen Can Undermine Aspirin

If you take daily aspirin for heart protection and also reach for ibuprofen for pain, you may be unknowingly canceling out aspirin’s benefit. Ibuprofen competes with aspirin for the same binding site on the COX-1 enzyme in platelets. When ibuprofen gets there first, it blocks aspirin from making its permanent mark, and since ibuprofen’s own effect on platelets is temporary, the net result is less antiplatelet protection.²⁷ In one study, combining immediate-release ibuprofen with 80 milligrams of aspirin reduced thromboxane suppression to below what 30 milligrams of aspirin alone could achieve.²⁸

Not all anti-inflammatory drugs cause this problem. The same study found that diclofenac did not interfere with aspirin’s antiplatelet effect.²⁸ If you need regular pain relief and are on daily aspirin, this is a conversation worth having with your doctor, because the choice of pain medication can meaningfully change whether your aspirin is actually working.

The Colorectal Cancer Connection

One of the most intriguing aspects of long-term aspirin use is its apparent ability to reduce colorectal cancer risk. Long-term follow-up data from randomized trials found that daily aspirin at doses between 75 and 500 milligrams reduced the 20-year risk of colon cancer by about 24% and deaths from colorectal cancer by 35%.²⁹ The benefit was concentrated in the proximal colon, where five or more years of aspirin use reduced cancer incidence by roughly 65 to 70%.³⁰ There was no added benefit at doses above 75 milligrams per day.³⁰

These are impressive numbers, but they come with important context. The cancer benefit requires years of continuous use to materialize and the follow-up periods in these analyses stretched to 20 years. The 2016 USPSTF had included colorectal cancer prevention as part of its rationale for recommending aspirin, but the 2022 update dropped that reasoning and focused solely on cardiovascular outcomes.¹⁰ This does not mean the cancer data evaporated. It reflects the difficulty of recommending a drug that takes a decade or more to show cancer benefits but starts causing bleeding harm immediately. For people with strong family histories of colorectal cancer, this is a nuanced discussion to have with their doctor.

Clopidogrel as an Alternative After Heart Procedures

For people who need long-term antiplatelet therapy after a coronary stent procedure, aspirin has traditionally been the default maintenance drug. But recent evidence suggests that clopidogrel, another antiplatelet agent, may work better in this setting. A meta-analysis of trials comparing the two drugs for secondary prevention after stent placement found that clopidogrel reduced major cardiovascular events by about 31% compared with aspirin, without increasing bleeding.³¹ A large randomized trial (SMART-CHOICE 3) in high-risk patients confirmed this, finding a three-year event rate of about 4.4% with clopidogrel versus 6.6% with aspirin, with no difference in bleeding.³²

This is an evolving area. It does not mean aspirin is the wrong choice for every post-stent patient, but it does mean that the automatic assumption of aspirin as the long-term maintenance drug is being questioned. If you have had a stent and are on long-term aspirin, newer alternatives may be worth asking your cardiologist about.

Aspirin Around Surgery

If you take daily aspirin and are scheduled for surgery, the question of whether to stop it beforehand is trickier than it sounds. Aspirin increases surgical bleeding, but stopping it exposes you to the cardiovascular rebound risk already described. A meta-analysis concluded that aspirin should only be discontinued before surgery when the bleeding risk of continuing it includes a realistic chance of death or severe consequences comparable to the cardiovascular risk of stopping.³³ A small randomized trial in high-risk patients undergoing non-cardiac surgery found that continuing aspirin through the perioperative period reduced cardiac events without significantly increasing bleeding, though the trial was not large enough to draw firm conclusions about bleeding alone.³⁴ The decision is almost always one your surgeon and cardiologist should make together, weighing the type of surgery, your underlying cardiovascular risk, and the specific bleeding risk of the procedure.