Aspirin is one of the most widely used medications in the world, but it carries real risks for certain groups of people. If you have a bleeding disorder, active stomach ulcers, severe kidney disease, or are in the third trimester of pregnancy, you should not take aspirin. The list extends further than most people realize, covering specific age groups, medical conditions, drug combinations, and even drinking habits.
Children and Teenagers
Children and adolescents with a fever or viral infection should not take aspirin. The concern is Reye’s syndrome, a rare but potentially fatal condition that damages the brain and liver. In the U.S., the FDA recommends against giving aspirin to anyone under 19 during episodes of fever. The UK sets the cutoff at 16. While a direct causal link between aspirin and Reye’s syndrome hasn’t been definitively proven, the association is strong enough that health authorities worldwide treat it as a firm rule. Use acetaminophen or ibuprofen for children’s fevers instead.
People With Bleeding Disorders
Aspirin works by making your blood less likely to clot. That’s useful for preventing heart attacks, but dangerous if your blood already has trouble clotting. People with inherited conditions like hemophilia should avoid all forms of aspirin. The same applies to anyone with an acquired bleeding tendency, such as during dengue or yellow hemorrhagic fever, where the body’s clotting ability is already compromised.
Active Stomach Ulcers or a History of GI Bleeding
Aspirin doubles the risk of upper gastrointestinal bleeding even at doses as low as 75 mg daily. If you currently have peptic ulcer disease or gastritis, aspirin makes bleeding significantly more likely. The risk is even more pronounced if you’ve bled from an ulcer before: up to 15 percent of people with a history of ulcer bleeding who take aspirin will experience recurrent bleeding within one year. That’s a strikingly high number for what many consider a mild, everyday medication.
Adults Over 60 Starting Aspirin for Heart Protection
For years, millions of older adults took a daily low-dose aspirin hoping to prevent a first heart attack or stroke. That guidance has changed. The U.S. Preventive Services Task Force now recommends against starting aspirin for primary cardiovascular prevention if you’re 60 or older. The reasoning is straightforward: both cardiovascular risk and bleeding risk rise with age, but the bleeding risk outpaces the heart benefit. For people already on aspirin for a known heart condition, this doesn’t apply. The new guidance is specifically about people without existing cardiovascular disease who were considering aspirin as a preventive measure.
For adults aged 40 to 59 with a 10 percent or greater 10-year cardiovascular risk, the decision is more nuanced. The net benefit is small, and it only tips in your favor if you’re not already at increased risk for bleeding. Even for those who do start aspirin in this age range, the data suggest considering stopping around age 75.
People With Aspirin-Sensitive Asthma
Some people with asthma have a specific reaction to aspirin that triggers breathing difficulties, nasal congestion, and sometimes severe asthma attacks. This condition, known as aspirin-exacerbated respiratory disease, typically involves a combination of asthma, nasal polyps, and aspirin sensitivity. It affects roughly 0.6 to 2.5 percent of all asthma patients, but aspirin intolerance shows up in as many as 20 percent of people with adult-onset asthma. If you have asthma and nasal polyps, aspirin could be particularly dangerous. Many people with this condition also react poorly to red wine and other alcoholic beverages.
People With Severe Kidney Disease
Your kidneys rely on certain protective compounds to maintain blood flow and function. Aspirin blocks the production of these compounds, which can accelerate kidney damage in people who already have impaired kidney function. The drug’s labeling recommends avoiding aspirin in patients with severe renal impairment, generally corresponding to a filtration rate below 30. If you have stage 4 or stage 5 chronic kidney disease, aspirin poses a real threat to your remaining kidney function.
Pregnancy, Especially the Third Trimester
Regular use of aspirin at standard pain-relief doses during the third trimester can cause serious problems for the baby. At doses above 300 mg daily from 30 weeks onward, aspirin is associated with premature closure of a critical blood vessel in the fetus called the ductus arteriosus. This vessel normally stays open until birth, and early closure can lead to dangerous changes in the baby’s lung circulation. Aspirin at these doses also raises the risk of bleeding complications during delivery for both mother and newborn.
It’s worth noting that some pregnant women are prescribed very low-dose aspirin (typically 81 mg) earlier in pregnancy to prevent preeclampsia. That’s a different situation, guided by a doctor, and doesn’t conflict with the warning about higher doses in the third trimester.
People Taking Blood Thinners or Other NSAIDs
Combining aspirin with other medications that affect clotting or irritate the stomach lining multiplies the risk of serious bleeding. Taking aspirin alongside another anti-inflammatory painkiller like ibuprofen or naproxen significantly increases the chance of upper gastrointestinal events. If you’re on a prescription blood thinner, adding aspirin creates a compounding effect on bleeding risk that can become dangerous quickly. A stomach-protecting medication can reduce some of this risk, but the combination still demands caution.
People With G6PD Deficiency
Glucose-6-phosphate dehydrogenase deficiency is a genetic condition that makes red blood cells vulnerable to destruction by certain triggers. Aspirin is one of those triggers. Taking it can set off an episode of acute hemolytic anemia, where red blood cells break apart faster than the body can replace them. This condition is more common in people of African, Mediterranean, and Southeast Asian descent, and many people carry it without knowing.
Heavy Alcohol Drinkers
If you regularly consume three or more alcoholic drinks per day, aspirin raises your risk of stomach bleeding considerably. This is serious enough that the FDA requires a warning on aspirin labels advising heavy drinkers to consult a doctor before using it. The risk applies even to low-dose aspirin, not just the higher doses used for pain relief. Alcohol irritates the stomach lining on its own, and aspirin compounds that irritation while simultaneously reducing the blood’s ability to stop the bleeding.
Before Surgery
If you’re scheduled for elective surgery, you’ll typically be asked to stop aspirin 5 to 10 days beforehand. Aspirin’s effect on your platelets lasts for the entire lifespan of those cells, which is about 7 to 10 days. That means a single dose taken a week before surgery can still increase bleeding during the procedure. Your surgeon will give you specific timing, but don’t wait for them to bring it up. Mention any aspirin use, even occasional, during your pre-surgical consultation.