Quick answer
What is aspirin used for?
Aspirin is a medicine that relieves pain and fever at standard doses, and at a low daily dose helps prevent heart attacks and strokes in people at high risk. It is not suitable for everyone, since it can cause stomach bleeding. During a suspected heart attack, one tablet is chewed while waiting for an ambulance, if not allergic to aspirin.
Aspirin has two very different uses
Aspirin (acetylsalicylic acid) is one of the oldest and most widely used medicines. At standard doses it relieves pain and reduces fever, while at a low daily dose it prevents blood clots, protecting against heart attack and stroke in people at high risk. These two uses require different doses and different medical guidance, so it is important not to confuse them.
Aspirin for pain and fever relief
Standard 300mg aspirin tablets are used for headache and migraine, period pain, toothache, muscle and joint aches, and fever. The typical dose is 300mg to 600mg every 4 to 6 hours as needed, up to a maximum of 4g (12 tablets) in 24 hours unless advised otherwise by a doctor. Taking it with or after food helps protect the stomach, and it is also available as dispersible tablets that dissolve in water before drinking.
Low-dose aspirin for heart and stroke prevention
A low daily dose of aspirin makes blood platelets less sticky, which reduces clot formation. It is used long-term in people who have had a heart attack, a stroke or TIA (mini-stroke), an angioplasty or stent insertion, or certain heart conditions that carry a high risk of clots.
Low-dose aspirin should never be started for prevention without GP advice, because the balance of benefit against bleeding risk depends on your individual cardiovascular risk, age and medical history. For people who have never had a heart event, aspirin is not routinely recommended as primary prevention.
Aspirin during a suspected heart attack
If you suspect a heart attack, call 999 first. The call handler may then advise chewing one 300mg aspirin tablet while waiting for the ambulance, but only if you are not allergic to aspirin and have not been told to avoid it. Chewing rather than swallowing the tablet whole allows faster absorption, but you should never delay calling 999 in order to find aspirin.
Side effects and risks of aspirin
Common side effects include stomach irritation, indigestion and nausea, along with an increased tendency to bleed, such as nosebleeds and bruising. More serious problems that need urgent help include stomach or gut bleeding, shown by black tarry stools or vomiting blood; an allergic reaction, causing wheezing, swelling or a rash; and Reye’s syndrome in children, which is why aspirin should never be given to anyone under 16.
Some people should avoid aspirin or use it only with caution, including those with a history of stomach ulcers or gastrointestinal bleeding, bleeding disorders, asthma triggered by aspirin or other NSAIDs, severe kidney or liver disease, pregnancy (especially in the third trimester, when paracetamol is preferred), and children and teenagers under 16.
Aspirin compared with ibuprofen and paracetamol
Paracetamol is gentler on the stomach and is the first choice for many people, including in pregnancy. Ibuprofen is an anti-inflammatory that should not be taken alongside aspirin without advice, since combining NSAIDs increases the risk of bleeding. Aspirin itself works as both an anti-inflammatory and an antiplatelet medicine, giving it a unique role in cardiovascular prevention at low doses. A pharmacist can help you choose the right option for your situation.
Taking aspirin safely
Take aspirin with food if it upsets your stomach, and always tell doctors and dentists that you take it, including before any surgery. Let them know before starting any anticoagulant such as warfarin or apixaban, and only stop taking aspirin on medical advice, since stopping suddenly after long-term use may increase the risk of a clot.
Enteric-coated aspirin
Some low-dose aspirin tablets have a gastro-resistant coating designed to reduce stomach irritation. This coating does not eliminate the bleeding risk entirely, so the same precautions still apply.
Aspirin and other medicines
Aspirin can interact with several other medicines. It increases bleeding risk when combined with warfarin or other anticoagulants, and with other NSAIDs such as ibuprofen or naproxen. Some SSRIs, a type of antidepressant, also raise the bleeding risk when taken alongside aspirin, and aspirin can affect how the body clears methotrexate. Always tell your GP and pharmacist about all the medicines you take.
When to see a GP about aspirin
See a GP before starting daily low-dose aspirin for heart protection, if you develop stomach pain, black stools or vomiting blood while taking aspirin, or if you find you need pain relief regularly, since the underlying cause should be assessed.
Children and aspirin
Aspirin should never be given to children under 16, especially during viral illnesses such as chickenpox or flu, because of the risk of Reye’s syndrome. Use an age-appropriate dose of paracetamol or ibuprofen for children instead.
Common questions about aspirin
- What is aspirin used for?
- Pain relief (headache, toothache, period pain), reducing fever, and at low daily doses (75mg) preventing blood clots in people who have had a heart attack, stroke, or TIA. It is also used briefly after some heart procedures and in certain arthritis conditions.
- What dose of aspirin should I take for pain?
- Standard tablets are 300mg — one to two tablets every 4 to 6 hours, maximum 12 tablets in 24 hours. Follow the packet. Low-dose 75mg tablets are for clot prevention, not pain — do not use them interchangeably without medical advice.
- Should I take aspirin to prevent a heart attack?
- Only if prescribed or recommended by a GP after assessing your individual risk. Low-dose aspirin prevents clots but increases bleeding risk — the balance favours aspirin in people who have already had a heart attack or stroke, but is less clear for people who have never had one.
- Can I take aspirin with other painkillers?
- Do not take aspirin with ibuprofen or other NSAIDs without advice — combined use increases stomach bleeding risk. Paracetamol can usually be taken alongside aspirin if needed. Check with a pharmacist.
- Why should children not take aspirin?
- Aspirin in children and teenagers (under 16) is linked to Reye's syndrome — a rare but serious liver and brain condition, especially after viral infections. Use paracetamol or ibuprofen for children instead.