Aspirin for prevention of blood clots

This leaflet is for parents and carers about how to use this medicine in children. Our information may differ from that provided by the manufacturers, because their information usually relates to adults. Read this leaflet carefully. Keep it somewhere safe so that you can read it again.

Your child should not take Aspirin if they have ever had a reaction to Aspirin or medicines known as non-steroidal anti-inflammatory drugs, used to treat inflammation.

Name of medicine

Aspirin (acetylsalicylic acid)

Brand names: Caprin, Micropirin, Nu-Seals aspirin

Why is it important for my child to take Aspirin?

Children who have heart or kidney problems may have an increased risk of blood clots. Blood clots can be dangerous if they form in the brain, lungs or heart. Taking aspirin regularly will help to reduce the risk of blood clots. (This is sometimes described as thinning the blood.)

Aspirin is also used after heart surgery and after organ transplants to reduce the risk of blood clots, and it may also be recommended for children who are at high risk of having a stroke.

You may have heard that aspirin should not be given to children because of the risk of a serious illness called Reye’s syndrome. However, for particular groups of children, the benefits of aspirin in reducing blood clotting far outweigh the risk of developing Reye’s syndrome. Ask your doctor if you are worried about this. More information is given below.

What is Aspirin available as?

Dispersible tablets: 75 mg, 300 mg

Enteric-coated tablets: 75 mg, 300 mg

These may contain lactose and aspartame.

When should I give Aspirin

Aspirin is usually given once each day. This is usually in the morning.

Give the medicine at about the same time(s) each day so that this becomes part of your child’s daily routine, which will help you to remember.

How much should I give?

Your doctor will work out the amount of Aspirin (the dose) that is right for your child. The dose will be shown on the medicine label.

It is important that you follow your doctor’s instructions about how much to give.

How should I give Aspirin?

Dispersible tablets

  • Disperse the tablet in a small amount of water, your doctor or pharmacist will tell you how much to use. Mix it vigorously – it will make a cloudy mixture. Give the mixture to your child straight away. You can give it using a medicine spoon or oral syringe.
  • Occasionally, the only way to provide the correct dose of Aspirin for your child will be to give part of a tablet or to disperse a tablet in a small amount of water and give some of the mixture. Your doctor or pharmacist will let you know if this is necessary and explain what to do. This method should only be used when you have been told to do it. Any unused mixture should be poured into a paper towel and put in the bin. Do not pour it down the sink.

Enteric-coated tablets

  • Tablets should be swallowed with a glass of water, squash or juice. Your child should not chew the tablet.

When should the medicine start working?

The medicine should start working after about 3 days, although you will not see any difference in your child.

What if my child is sick (vomits)?

  • If your child is sick less than 30 minutes after having a dose of Aspirin, give them the same dose again.
  • If your child is sick more than 30 minutes after having a dose of Aspirin, do not give them another dose. Wait until the next normal dose.

If your child is sick again, seek advice from your family doctor, nurse, pharmacist, or hospital. They will decide what to do based on your child’s condition and the specific medicine involved.

What if I forget to give it?

If you remember before bedtime, give the missed dose. You do not need to wake up a sleeping child to give a missed dose.

If you have missed more than one dose, contact your doctor or pharmacist for advice.

What if I give too much?

If you think you may have given your child too much Aspirin, contact your doctor or local NHS services (details at end of leaflet). Have the medicine or packaging with you if you telephone for advice.

Are there any possible side effects?

We use medicines to make our children better, but sometimes they have other effects that we don’t want (side effects).

Side effects you must do something about

If your child gets bad stomach pain, brings up (vomits) blood or their stools (poo) are very dark, contact your doctor or take your child to hospital straight away, as they may have an ulcer.

If your child gets severe vomiting and has viral symptoms (fever [temperature above 38°C], aches and pains), contact your doctor straight away, in case they have Reye’s syndrome

If your child gets a rash in the first 2 weeks of taking Aspirin, contact your doctor straight away, as they may be allergic to Aspirin. Do not give any more medicine until you have spoken to your doctor.

If your child has asthma, they may get more attacks than usual. If this happens, contact your doctor for advice.

Other side-effects you need to know about

  • Your child may get stomach cramps and stomach pain when they first start taking Aspirin. If this is still a problem after a week, contact your doctor. Giving each dose with some food may help.

There may sometimes be other side effects that are not listed above. If you notice anything unusual and are concerned, contact your doctor. You can report any suspected side effects to a UK safety scheme at

Can other medicines be given at the same time as Aspirin?

  • You can give your child medicines that contain paracetamol, unless your doctor has told you not to.
  • Do not give your child ibuprofen, anti-coagulants (for example, warfarin), or other medicines called non-steroidal anti-inflammatory drugs, unless your doctor has said that you can.
  • Check with your doctor or pharmacist before giving any other medicines to your child. This includes herbal and complementary medicines.

Is there anything else I need to know about this medicine?

Aspirin is one of a group of drugs called non-steroidal anti-inflammatory drugs (NSAIDs). If your child has previously reacted to other drugs of this type, you should tell your doctor before starting Aspirin.

  • You may have heard that aspirin should not be given to children because of the risk of Reye’s syndrome. This is a very rare but dangerous disease that affects the brain and liver. Children affected have mostly been less than 5 years of age and have had a viral illness such as chicken pox. It has sometimes affected older children and teenagers. Contact your doctor to discuss whether to stop or continue the aspirin.
  • For children at risk, the benefits of low-dose aspirin in reducing blood clots far outweigh the risk of your child developing Reye’s syndrome.
  • Higher doses of aspirin are sometimes used in a rare illness called Kawasaki disease and for rheumatic fever.

General advice about medicines

  • Try to give medicines at about the same times each day, to help you remember.
  • Only give this medicine to your child. Never give it to anyone else, even if their condition appears to be the same, as this could do harm.
  • Make sure that you always have enough medicine. Order a new prescription at least 2 weeks before you will run out.
  • Make sure that the medicines you have at home have not reached the ‘best before’ or ‘use by’ date on the packaging. Give old medicines to your pharmacist to dispose of.

Where should I keep this medicine?

  • Keep the medicine in a cupboard, away from heat and direct sunlight.
  • It does not need to be kept in the fridge.
  • Make sure that children cannot see or reach the medicine.
  • Keep the medicine in the container it came in.

Who to contact for more information?

Your child’s doctor, pharmacist or nurse will be able to give you more information about Aspirin and about other medicines used to treat or prevent blood clots.

England: NHS 111

Tel 111

Scotland: NHS 24

Northern Ireland: NI Direct

Wales: NHS Direct

Tel 111 (free) or 0845 46 47 (2p per minute)

Copyright disclaimer

Version [2]. © NPPG, RCPCH and WellChild, all rights reserved. Review by June 2017.

The primary source for the information in this leaflet is the British National Formulary for Children. For details on any other sources used for this leaflet, please contact us through our website,

We take great care to make sure that the information in this leaflet is correct and up-to-date. However, medicines can be used in different ways for different patients. It is important that you ask the advice of your doctor or pharmacist if you are not sure about something. This leaflet is about the use of these medicines in the UK, and may not apply to other countries. The Royal College of Paediatrics and Child Health (RCPCH), the Neonatal and Paediatric Pharmacists Group (NPPG), WellChild and the contributors and editors cannot be held responsible for the accuracy of information, omissions of information, or any actions that may be taken as a consequence of reading this leaflet.