Aspirin is safe for most adults when used appropriately, but it carries real risks that have shifted medical guidance significantly in recent years. The biggest change: routine daily aspirin is no longer recommended for preventing a first heart attack or stroke in most people, especially those 60 and older. Whether aspirin is safe for you depends on your age, your reason for taking it, and what other medications you use.
How Aspirin Works in the Body
Aspirin permanently disables an enzyme in your platelets, the small blood cells responsible for clotting. This makes platelets less sticky and reduces the chance of a clot forming inside a blood vessel. That anti-clotting effect is why aspirin helps prevent heart attacks and certain strokes. It’s also why aspirin’s main safety concern is bleeding: the same mechanism that stops dangerous clots also makes it harder for your body to stop bleeding when it needs to.
Unlike a pain reliever you take once and forget, aspirin’s effect on each platelet lasts for the platelet’s entire lifespan, roughly 7 to 10 days. This is why surgeons ask you to stop aspirin well before a procedure, and why even low doses have a meaningful impact on your body’s clotting ability.
The Bleeding Risk Is Real but Measurable
The most common serious side effect of daily aspirin is gastrointestinal bleeding. A large randomized trial of over 19,000 older adults found that aspirin increases overall GI bleeding risk by about 60%. Upper GI bleeding, the more dangerous kind, was 87% more likely in the aspirin group compared to placebo. In practical terms, that translated to about 2.1 upper GI bleeding events per 1,000 people per year on aspirin versus 1.1 per 1,000 on placebo.
Those numbers mean the absolute risk for any one person is still small, but it adds up over years of daily use. The risk climbs with age, and it’s higher if you have a history of stomach ulcers, take blood thinners, or drink alcohol regularly.
Beyond the gut, aspirin also increases the risk of hemorrhagic stroke (bleeding in the brain) by about 25%, based on a meta-analysis of primary prevention trials. That same analysis found aspirin did not reduce the overall risk of stroke or death from any cause. It did lower heart attack risk by 16% in older studies, but more recent trials showed a weaker benefit, likely because modern treatments for high blood pressure and cholesterol have already reduced baseline heart attack rates.
Current Guidelines for Heart Disease Prevention
The U.S. Preventive Services Task Force updated its recommendation in 2022, and the shift was notable. For adults 60 and older who have never had a heart attack or stroke, the task force now recommends against starting daily aspirin for prevention. The reasoning is straightforward: both heart disease risk and bleeding risk increase with age, and by 60, the bleeding danger catches up to or exceeds the cardiovascular benefit.
For adults aged 40 to 59 with a 10% or greater estimated 10-year risk of cardiovascular disease, the decision is more nuanced. The task force calls the net benefit “small” and says it should be an individual choice. People in this group who don’t have elevated bleeding risk and are comfortable with daily use are more likely to benefit. The recommended dose, if you and your doctor decide to proceed, is 81 mg per day.
For people who already have heart disease or have had a heart attack or stroke, the calculus is different. In that situation, daily aspirin remains a standard part of treatment because the risk of another cardiovascular event is high enough to clearly outweigh the bleeding risk. If your doctor prescribed aspirin after a cardiac event, don’t stop taking it without a conversation.
Low Dose vs. Standard Dose
Most people who take daily aspirin use the 81 mg “baby aspirin” rather than the 325 mg tablet. A large trial published in the New England Journal of Medicine compared the two doses in patients with established cardiovascular disease and found no significant difference in either cardiovascular protection or major bleeding. The notable finding: over 40% of patients assigned to 325 mg switched down to 81 mg on their own during the study, suggesting the higher dose is harder to tolerate day after day. At 81 mg, patients stuck with their assigned dose far more consistently.
Enteric Coating Doesn’t Protect Your Stomach
Many people choose enteric-coated aspirin believing it’s gentler on the stomach. The evidence says otherwise. A systematic review found that enteric-coated aspirin provides no meaningful protection against peptic ulcers or GI bleeding compared to plain aspirin. The reason is that aspirin’s damage to the stomach lining is primarily a systemic effect, meaning it happens through the bloodstream after absorption, not just from direct contact with the stomach wall. In one trial, patients taking enteric-coated aspirin actually experienced more GI bleeding than those on placebo (0.96% vs. 0.46%).
If you’re concerned about stomach damage from daily aspirin, a proton pump inhibitor (a common acid-reducing medication) taken alongside aspirin has been shown to significantly reduce GI injury. Switching to enteric-coated aspirin alone will not.
Ibuprofen Can Cancel Aspirin’s Benefits
If you take daily aspirin for heart protection, regular use of ibuprofen or similar anti-inflammatory painkillers can block aspirin’s ability to prevent clots. Both drugs compete for the same binding site on platelets, but ibuprofen gets there first and wears off, leaving the platelet unprotected for part of the day. A study in Circulation found that people taking ibuprofen regularly (60 or more days per year) while on aspirin had nearly three times the risk of heart attack compared to aspirin users who didn’t take ibuprofen.
Occasional ibuprofen use didn’t show the same problem. And notably, acetaminophen (Tylenol) does not interfere with aspirin’s anti-clotting effect at all. If you take daily aspirin and need a pain reliever, acetaminophen is the safer pairing. If you must take ibuprofen, taking your aspirin at least 30 minutes beforehand may help, though this workaround doesn’t fully solve the problem with repeated ibuprofen doses throughout the day.
Aspirin and Kidney Function
A large study of over 385,000 U.S. veterans with early-stage kidney disease found that long-term low-dose aspirin use was associated with a 30% higher odds of faster decline in kidney function compared to non-use. Aspirin did not, however, increase the risk of progressing to kidney failure requiring dialysis, and it showed no mortality benefit in this population either. For people with existing kidney disease, aspirin’s role is uncertain, and the potential for accelerating kidney function decline is worth factoring into any decision about daily use.
Aspirin and Children: Reye’s Syndrome
Aspirin is not safe for children and teenagers during viral illnesses. It’s linked to Reye’s syndrome, a rare but potentially fatal condition that causes swelling in the liver and brain. Reye’s syndrome can occur at any age but is most common in children and teens recovering from a viral infection like the flu or chickenpox. Because of this risk, acetaminophen or ibuprofen are the recommended alternatives for fever and pain in anyone under 18. Salicylate, the active ingredient in aspirin, also appears in some other over-the-counter products, so checking labels matters.
Aspirin Sensitivity and Respiratory Reactions
Some people have a genuine intolerance to aspirin that goes beyond stomach irritation. A condition known as aspirin-exacerbated respiratory disease affects roughly 7 to 15% of people with severe asthma and about 9% of those with chronic sinus disease and nasal polyps. It typically appears in adulthood and involves a triad of symptoms: aspirin sensitivity, nasal polyps, and asthma. Taking aspirin or other anti-inflammatory drugs triggers reactions ranging from nasal congestion and flushing to full asthma attacks and throat tightening. People with adult-onset asthma who notice their breathing worsens after taking aspirin or ibuprofen should be evaluated for this condition, as continued exposure can provoke severe reactions.