What aspirin is used for
Aspirin, or acetylsalicylic acid, was once the most common medicine for pain and fever. Today its main use is different. Doctors prescribe low-dose aspirin to stop blood clots forming in people who have had a heart attack, a stent, bypass surgery, a mini-stroke or a stroke caused by a clot. In these people, it lowers the chance of another event.
Aspirin is still sometimes used for headache, pain and inflammation, but safer options such as paracetamol are usually preferred. Doctors also use it in certain special situations, such as some pregnancy conditions and specific inflammatory diseases, but only under close supervision.
- Preventing repeat heart attacks and strokes, on prescription
- After heart stents or bypass surgery
- Some pregnancy and inflammatory conditions, under a specialist
- Occasionally for pain in adults
How aspirin works
Aspirin blocks enzymes that make prostaglandins, which cause pain and swelling, and a substance called thromboxane in platelets. Platelets are tiny blood cells that stick together to form clots. Aspirin makes platelets less sticky for the rest of their life, which is several days, so clots are less likely to block the arteries of the heart or brain.
This anti-clotting effect is useful for people at high risk of heart attack or stroke, but it also explains the main downside. Because blood clots less easily, cuts bleed longer and the stomach lining is more likely to bleed. Doctors weigh this bleeding risk against the benefit for each person, which is why aspirin for the heart is a medical decision rather than a general health habit.
Aspirin side effects: common and serious
Common side effects include acidity, indigestion, nausea and easy bruising. Some people notice that small cuts or nosebleeds take longer to stop. Taking aspirin after food can reduce stomach discomfort. Mild symptoms often settle, but ongoing acidity or stomach pain should be reported to your doctor rather than ignored or treated with extra painkillers.
Serious side effects include stomach or intestinal bleeding, which may show as black stools or vomiting blood, and, rarely, bleeding in the brain. Aspirin can trigger wheezing in some people with asthma and nasal polyps. Allergic reactions such as hives or face swelling can occur. Ringing in the ears may signal too much aspirin.
Who should avoid aspirin or take extra care
Aspirin must not be given to children and teenagers under sixteen for fever or viral illness, because it is linked to Reye's syndrome, a rare but dangerous condition affecting the liver and brain. It should also be avoided when dengue is suspected, as it increases bleeding.
People with stomach ulcers, bleeding disorders, severe kidney or liver disease, uncontrolled high blood pressure or aspirin-sensitive asthma need a doctor's advice before use. In pregnancy it is only used when a doctor specifically prescribes it. Elderly people have a higher bleeding risk. Healthy people with no heart disease should not start daily aspirin on their own, as the bleeding risk may outweigh any benefit.
Aspirin interactions to know
Taking aspirin with other painkillers like ibuprofen or diclofenac raises the risk of stomach bleeding, and ibuprofen can reduce aspirin's heart-protecting effect. Combining it with blood thinners such as warfarin or other anti-platelet medicines increases bleeding. Doctors sometimes deliberately prescribe two anti-platelet medicines together after a stent, but that is always their decision.
Steroid tablets, some antidepressants and alcohol also add to the bleeding risk. Aspirin can affect methotrexate levels and some diabetes and gout medicines. Before any dental extraction or surgery, tell the dentist or surgeon that you take aspirin, but do not stop it without asking the doctor who prescribed it.
Practical tips for safe use
If a doctor has prescribed aspirin for your heart, take it exactly as directed and do not stop suddenly, because stopping can increase the risk of a heart attack or stent blockage. Aspirin for heart protection is only on a doctor's prescription.
Take it after food to protect the stomach. Watch for signs of bleeding such as black stools, blood in urine or unusual bruising. Keep a list of your medicines and show it to every doctor and chemist, so that painkillers that clash with aspirin are not added without thought.
When to talk to your doctor about aspirin
Seek urgent care for vomiting blood, black stools, sudden severe headache, confusion or weakness on one side of the body. See your doctor if you have new acidity or bruising while on aspirin. Always ask your doctor or pharmacist before starting, stopping or combining aspirin with other medicines.
Related medicines
Only your doctor can decide which medicine, dose and combination is right for you.
- Clopidogrel (anti-platelet medicine)Another medicine that stops platelets clumping, often used after stents.Only on a doctor's prescription; it also raises bleeding risk.
- Paracetamol (fever and pain reliever)Preferred for everyday pain and fever.Does not protect the heart and must not be overdosed.
- Proton pump inhibitors such as pantoprazoleProtect the stomach in people at high bleeding risk on aspirin.Used when a doctor decides the stomach needs protection.
- Statins such as atorvastatinLower cholesterol and are often prescribed alongside aspirin after a heart attack.Only on a doctor's prescription.
See a doctor urgently if
- Vomiting blood or material like coffee grounds, or passing black stools
- Sudden severe headache, confusion, slurred speech or one-sided weakness
- Wheezing, face swelling or hives soon after a dose
- Ringing in the ears with nausea, fast breathing or confusion
- A child or teenager given aspirin who becomes drowsy, confused or keeps vomiting
Tests that may help
This article is general health information, not medical advice. Do not start, stop or combine medicines on your own — always follow your doctor's prescription and ask your pharmacist if unsure.