Antiplatelets, aspirin, low dose

Aspirin is an antiplatelet medicine, which means it reduces the risk of clots forming in your blood. This reduces your risk of having a stroke or heart attack.

Normally, when there is a cut or break in a small blood vessel, a blood clot forms to plug the hole until the blood vessel heals.

Small cells in the blood called platelets make the blood clot. When a platelet detects a damaged area of a blood vessel, it produces a chemical that attracts other platelets and makes them stick together to form a blood clot.

Aspirin reduces the ability of the platelets to stick together and reduces the risk of clots forming.

When is low-dose aspirin used?

Low-dose aspirin (usually 75mg a day) may be given to you if you have had:

a heart attack
a stroke or transient ischemic attack (TIA)
acute coronary syndrome (minor heart attack or unstable angina)
a coronary artery bypass operation
a bioprosthetic heart valve
a vascular operation
a stent put into any one of the arteries in your body

It may also be given to you if you are considered at risk of having a heart attack or stroke. You may be considered at risk if you:

Treatment with an antiplatelet medicine such as aspirin is usually for life.

Higher doses of aspirin may be given for other conditions, but these pages focus on the use of low-dose aspirin.

Children

Aspirin may be given to children under specialist supervision after heart surgery, or to treat children with Kawasaki disease.

Aspirin must not be given to anyone under 16 years old, unless under specialist advice.

Things to consider

Aspirin may not be suitable to take if you have certain health conditions.

When to avoid aspirin

Low-dose aspirin should not be taken if you:

have an active (bleeding) peptic ulcer
have recently had a stroke caused by bleeding
have haemophilia or any other bleeding disorder
are allergic to aspirin or to non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or diclofenac
have severe liver or kidney problems
are taking certain medications – read information about how aspirin interacts with other medicines

Aspirin must not be given to anyone under 16 years old, unless under specialist advice.

Pregnancy and breastfeeding

If you are pregnant or breastfeeding, only take low-dose aspirin (75mg) on the recommendation of your doctor.

It is also important not to take aspirin at doses higher than 100mg per day during the last three months of pregnancy because this can lead to complications in the mother or baby.

Using aspirin with caution

Tell your doctor before taking low-dose aspirin if you have:

asthma
heavy periods
uncontrolled high blood pressure
a history of gout
a history of problems with your stomach, small intestine, liver, kidneys or heart

Occasionally, some people are advised to stop taking aspirin seven days before a planned operation. For some people this may include minor surgery, such as a tooth extraction. Seek advice from your doctor or surgeon before you stop taking any medication.

Side effects and interactions

Aspirin can cause side effects, although serious reactions are rare.

See your doctor if you are worried or continue to experience any side effects while taking low-dose aspirin.

Common side effects may include:

indigestion
increased risk of bleeding

However, less than 10% of people taking aspirin experience these side effects. If you experience indigestion, try sticking to basic food and taking your aspirin after a meal.

Allergic reaction

In some cases aspirin can cause an allergic reaction, although this is more common in people who have asthma. Go to the nearest hospital's accident and emergency department (A&E) if you experience:

swelling of the lips, mouth or throat
breathing problems
a skin rash which appears quickly

Uncommon or rare side effects

Other, rarer side effects of aspirin may include:

a runny nose
headache
ringing in the ears (tinnitus)
vertigo
a raised, itchy rash on the skin (hives)
nausea or vomiting
worsening of asthma caused by narrowing of airways
inflammation (swelling) of the stomach
bleeding in the stomach
bruising

In extremely rare cases, a possible side effect of taking low-dose aspirin is haemorrhagic stroke (bleeding in the brain).

Reporting side effects

The Yellow Card Scheme allows you to report suspected side effects from any type of medicine you are taking.

It is run by a medicines safety watchdog called the Medicines and Healthcare products Regulatory Agency (MHRA). See the website of the Yellow Card Scheme for more information.

Missed doses

If you forget to take your dose of aspirin, take that dose as soon as you remember and then continue to take your course of aspirin as normal.

However, if it is almost time for the next dose, skip the missed dose and continue your regular schedule. Do not take a double dose to make up for a missed one.

Extra doses

The patient information leaflet that comes with your medicine includes advice about what to do if you miss a dose.

If you accidentally take an extra dose of low-dose aspirin, it is unlikely to cause you harm as larger doses of aspirin are given safely for other conditions.

However, if you feel unwell or are concerned, speak to your GP or pharmacist, or call NHS 111.