What side effects can aspirin cause?
Aspirin (acetylsalicylic acid) can cause side effects in several body systems, but the most important to watch for are bleeding-related effects (because aspirin can make blood less able to clot) and stomach irritation.
Common side effects include:
- Stomach pain or burning, heartburn, nausea, vomiting
- Increased risk of stomach or intestinal bleeding, which can show up as black/tarry stools or vomiting blood
- Dizziness or headache
Less common but serious side effects include:
- Allergic reactions, including hives, facial swelling, or wheezing
- Severe bleeding or anemia from chronic blood loss
- Kidney problems (especially in people who already have kidney disease or take certain other medicines)
- Liver problems (rare)
Who is at higher risk for serious aspirin side effects?
Risk is higher in people who:
- Have a history of stomach ulcers or gastrointestinal bleeding
- Take other medicines that also raise bleeding risk (for example, anticoagulants or other blood thinners, and some NSAIDs)
- Have uncontrolled high blood pressure, significant liver disease, or kidney disease
- Have asthma that worsens with aspirin or other NSAIDs
- Take high aspirin doses (or combine aspirin with alcohol)
- Are older adults, who are more prone to GI bleeding and kidney issues
When should someone seek urgent help?
Get emergency care if aspirin causes signs of serious bleeding or a severe allergic reaction, such as:
- Black, tarry stools
- Vomiting blood or material that looks like coffee grounds
- Trouble breathing, swelling of the face/throat, or widespread hives
- Severe or worsening abdominal pain
- Fainting, severe weakness, or symptoms of shock
How do side effects differ by dose and use (pain relief vs daily low-dose)?
The side-effect profile is influenced by dose and why aspirin is being taken:
- Low-dose (often used for cardiovascular prevention) still increases bleeding risk, but at generally lower rates than higher doses.
- Higher doses (often used for pain or fever) tend to increase the chance of stomach irritation and GI bleeding.
If you’re taking aspirin regularly, it’s especially important to discuss whether the benefits outweigh bleeding risks for your situation.
Can aspirin cause stomach bleeding even if it doesn’t hurt your stomach?
Yes. Some people develop gastrointestinal bleeding without obvious warning pain. That’s why looking for “red flag” signs matters, such as black/tarry stools, vomiting blood, or symptoms of anemia (fatigue, pale skin, shortness of breath).
What medication interactions raise aspirin side-effect risk?
Some combinations can increase bleeding risk or other adverse effects. Common categories include:
- Blood thinners (anticoagulants)
- Other antiplatelet medicines
- Other NSAIDs (for example, ibuprofen or naproxen)
- Some antidepressants (certain types can raise bleeding risk)
- Alcohol use (can increase GI bleeding risk)
If you tell me which medicines you take, I can help identify the interaction risks to discuss with a clinician or pharmacist.
What about aspirin and children/teens?
Aspirin is generally not recommended for children or teens with viral illnesses (like flu or chickenpox) because of the risk of Reye’s syndrome, a rare but serious condition.
What are patient questions about aspirin side effects?
People often ask:
- “Is it normal to get stomach upset?” Mild stomach irritation can happen, but ongoing symptoms or any bleeding signs should be taken seriously.
- “Can I switch to a different pain reliever?” Alternatives depend on your health history and what you’re treating; options may differ for people with bleeding risk.
- “Should I stop if I notice side effects?” Don’t stop or change preventive aspirin without medical advice, especially if it was prescribed for heart or stroke prevention.
If you share your age, dose (low-dose vs higher dose), reason for taking aspirin, and any other meds you take, I can narrow down which side effects are most relevant to you.