Aspirin is an everyday painkiller for aches and pains such as headachetoothache and period pain. It can also be used to treat colds and flu-like symptoms, and to bring down a high temperature.

Aspirin is known as an acetylsalicylic acid. It also belongs to a group of medicines called non-steroidal anti-inflammatory drugs (NSAIDs).

Aspirin combined with other ingredients is also available in some cold and flu remedies.

You can buy most types of aspirin from pharmacies, shops and supermarkets. Some types are only available on prescription.

Aspirin comes as tablets or suppositories – medicine that you push gently into your anus (bottom). It also comes as a gel for mouth ulcers and cold sores.

If you've had a stroke or heart attack, or are at high risk of a heart attack, your doctor may recommend that you take a daily low-dose aspirin. Some women may also be prescribed low-dose aspirin while they’re pregnant.

This is different to taking aspirin for pain relief. Only take low-dose aspirin if your doctor recommends it. 

Key facts

  • It's best to take aspirin with food. That way, you'll be less likely to get an upset stomach or stomach ache.
  • Never give aspirin to children under the age of 16 (unless their doctor prescribes it). It can make children more likely to develop a very rare but serious condition called Reye's syndrome.
  • You should start to feel better 20 to 30 minutes after taking aspirin.
  • Aspirin is an ingredient in combined medicines such as Anadin Original, Anadin Extra, Alka-Seltzer Original, Alka-Seltzer XS and Beechams Powders.
  • Aspirin as a mouth gel has the brand name Bonjela. Like other aspirin products, it's only for people aged 16 and over. Bonjela Teething Gel and Bonjela Junior Gel do not contain aspirin, so you can give them to children under 16.

Who can and cannot take it

Who can take aspirin

Most people aged 16 and over can safely take aspirin.

Who may not be able to take aspirin

Aspirin is not suitable for some people.

There is a possible link between aspirin and Reye's syndrome in children. Reye's syndrome is a very rare condition that can cause serious liver and brain damage.


Never give aspirin to children under 16, unless their doctor prescribes it.

To make sure aspirin as a painkiller (including mouth gel) is safe for you, tell your doctor or pharmacist if you:

  • have ever had an allergy to aspirin or similar painkillers such as ibuprofen
  • have ever had a stomach ulcer
  • have recently had a stroke (although depending on the kind of stroke you've had, your doctor may recommend that you take low-dose aspirin to prevent another one)
  • have high blood pressure (hypertension)
  • have indigestion
  • have asthma or lung disease
  • have ever had a blood clotting problem
  • have liver or kidney problems
  • have gout – it can get worse for some people who take aspirin
  • have heavy periods – they can get heavier with aspirin
  • are pregnant, trying to get pregnant or breastfeeding

How and when to take it

Dosage and strength

The dose of aspirin that's right for you depends on the kind of aspirin you're taking, why you're taking it and how well it helps your symptoms.

Dosage and strength of aspirin tablets

Aspirin usually comes as 300mg tablets.

The usual dose is 1 or 2 tablets, taken every 4 to 6 hours.


Do not take more than 12 tablets in 24 hours. Wait at least 4 hours between doses.

Dosage and strength of aspirin suppositories

Aspirin suppositories come in 2 strengths. They contain 150mg or 300mg of aspirin. You can buy them from a pharmacy.

If you're using:

  • 150mg – the usual dose is 3 to 6 suppositories, this is 450mg to 900mg, used every 4 hours. The maximum dose is 24 of the 150mg suppositories in 24 hours.
  • 300mg – the usual dose is 1 to 3 suppositories, this is 300mg to 900mg, used every 4 hours. The maximum dose is 12 of the 300mg suppositories in 24 hours.

If you need a dose of 450mg or 750mg, your doctor or pharmacist will give you a mixture of strengths and explain how to use them.


Do not use more than 24 of the 150mg suppositories or 12 of the 300mg in 24 hours. Wait at least 4 hours between doses.

How to take it

Different aspirin tablets and how to take them

Aspirin tablets come as different types including:

  • standard tablets that you swallow whole with water
  • soluble tablets that you dissolve in a glass of water
  • enteric coated tablets that you swallow whole with water

Enteric tablets have a special coating that are gentler on your stomach. Do not chew or crush them because it will stop the coating working. If you also take indigestion remedies, take them at least 2 hours before or after you take your aspirin. The antacid in the indigestion remedy affects the way the coating on these tablets works.

You can buy standard aspirin tablets and soluble tablets from both pharmacies and supermarkets.

How to use aspirin suppositories

Aspirin suppositories are medicine that you push gently into your anus (bottom).

Read the instructions in the leaflet that comes with the suppositories.

  • Go to the toilet beforehand if you need to.
  • Wash your hands before and afterwards. Also clean around your anus with mild soap and water, rinse and pat dry.
  • Unwrap the suppository.
  • Stand with one leg up on a chair or lie on your side with one leg bent and the other straight.
  • Gently push the suppository into your anus with the pointed end first. It needs to go in about 2cm to 3cm (1 inch).
  • Sit or lie still for about 15 minutes. The suppository will melt inside your anus.

How to use aspirin mouth gel

For mouth ulcers or sores, massage about a centimetre (half an inch) of gel onto the sore area. Apply it to the inside of your mouth or gums every 3 hours as needed.

If you have dentures (false teeth), take them out before you apply the mouth gel. Then wait at least 30 minutes after applying the gel before putting your dentures back in your mouth.

You can buy aspirin mouth gel (Bonjela) from pharmacies and supermarkets. Do not use Bonjela on children. You can give Bonjela Teething Gel or Bonjela Junior to children as they do not contain aspirin.

How long to take aspirin for

If you're taking aspirin for a short-lived pain, like toothache or period pain, you may only need to take it for 1 or 2 days.

If you've bought it from a shop, supermarket or pharmacy and need to use aspirin for more than 3 days, ask your doctor or pharmacist for advice.

If your doctor has prescribed your aspirin, take it for as long as they recommend.

If you take too much

Taking or using 1 or 2 extra tablets or suppositories is unlikely to be harmful.

The amount of aspirin that can lead to overdose varies from person to person.

Contact 111 Wales for advice now if:

You take more than the daily limit of 12 tablets in 24 hours and get side effects such as:

  • feeling sick (nausea)
  • ringing in the ears (tinnitus)
  • hearing problems
  • confusion
  • feeling dizzy

If you need to go to A&E, do not drive yourself – get someone else to drive you or call for an ambulance.

Take the aspirin packet or leaflet inside it, plus any remaining medicine, with you.

Side effects

Like all medicines, aspirin can cause side effects although not everyone gets them.

It's best to take the lowest dose that works for you for the shortest possible time. That way, there's less chance that you'll get unwanted side effects.

Common side effects

These common side effects of aspirin for pain relief happen in more than 1 in 100 people. There are things you can do to help cope with them.

Mild indigestion

Take your aspirin with food to prevent this. If you still get indigestion or it does not go away, it could be a sign that the aspirin has caused a stomach ulcer. Talk to your doctor as they may prescribe something to protect your stomach or switch you to a different medicine.

Bleeding more easily than normal

Be careful when doing activities that might cause an injury or a cut. It might be best to stop doing contact sports such as football, rugby and hockey, while you're taking aspirin. Wear gloves when you use sharp objects like scissors, knives, and gardening tools. Use an electric razor instead of wet shaving, and use a soft toothbrush and waxed dental floss to clean your teeth. See a doctor if you're worried about any bleeding.

Talk to your doctor or pharmacist if the side effects bother you or do not go away.

Serious side effects

It happens rarely, but some people have serious side effects after taking aspirin.

Call your doctor or call 111 Wales now if:

  • you cough up blood or have blood in your pee, poo or vomit
  • the whites of your eyes turn yellow or your skin turns yellow (this may be less obvious on brown or black skin), or your pee gets darker) – this can be a sign of liver problems
  • the joints in your hands and feet are painful – this can be a sign of high levels of uric acid in the blood
  • your hands or feet are swollen – this can be a sign of water retention

Stomach ulcers

Aspirin can cause ulcers in your stomach or gut, especially if you take it for a long time or in big doses. Your doctor may tell you not to take aspirin if you have a stomach ulcer, or if you've had one in the past.

If you're at risk of getting a stomach ulcer and you need a painkiller, take paracetamol instead of aspirin as it's more gentle on your stomach.

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to aspirin.

Call 999 now if:

  • your lips, mouth, throat or tongue suddenly become swollen
  • you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
  • your throat feels tight or you're struggling to swallow
  • your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
  • you suddenly become very confused, drowsy or dizzy
  • someone faints and cannot be woken up
  • a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

Other side effects

These are not all the side effects of aspirin. For a full list see the leaflet inside your medicines packet.

You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

Pregnancy, breastfeeding and fertility

Pregnancy and aspirin

Paracetamol is recommended as the first choice of painkiller for pregnant women.

There is a difference between high dose aspirin (300mg tablets) and low dose aspirin (75mg 150mg per day). Low-dose aspirin may be prescribed by your doctor or midwife to help prevent a condition called pre-eclampsia and is safe to take throughout pregnancy.

However, high dose aspirin is not recommended for pain relief in pregnancy as it may affect the baby’s circulation, especially if taken for long periods of time after 30 weeks. If paracetamol does not control your pain, ask a doctor for advice before taking aspirin. While there’s no strong evidence that high dose aspirin is unsafe to take during the first 6 months of pregnancy (up to 30 weeks), other painkillers may be more suitable and potentially less harmful to your baby.

If you've taken high dose aspirin after week 30 of pregnancy, especially if you've taken it for a long time, tell your doctor or midwife as soon as possible so they can check the health of your baby.

If you’re pregnant, or having fertility treatment, you may be prescribed low-dose aspirin by your doctor, a pregnancy specialist (obstetrician) or some midwives. Find out about more about low-dose aspirin.

Breastfeeding and aspirin

Paracetamol or ibuprofen are recommended to control pain or a high temperature while you’re breastfeeding.

Aspirin is not usually recommended as a painkiller while you are breastfeeding, but if other painkillers are not suitable your doctor may tell you to take aspirin. Ask your doctor for advice before taking it.

Aspirin passes into breast milk in small amounts. There is a possible link between aspirin and Reye's syndrome in children. If your baby develops a viral infection or a high temperature, stop taking aspirin until your baby is well again. Alternatively, you can express milk, throw the milk away and give your baby formula. This will maintain your supply of milk until your baby is better and you can then carry on breastfeeding.

If you notice that your baby is not feeding as well as usual, seems to be bruising or bleeding easily, or has a rash, or if you have any other concerns about your baby, talk to your health visitor, midwife, pharmacist, or doctor as soon as possible.

Fertility and aspirin

There's no clear evidence to suggest that taking aspirin will reduce fertility in either men or women.

However, if you're trying to get pregnant speak to a pharmacist or your doctor about it. They may want to review your treatment.

Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

Find out more about how aspirin can affect you and your baby during pregnancy on the Best Use of Medicines in Pregnancy (BUMPS) website.


Cautions with other medicines

Some medicines affect the way aspirin works.

Tell your doctor if you're taking these medicines before you start taking aspirin:

  • medicines to prevent blood clots such as clopidogrel, apixaban, edoxaban, dabigatran, rivaroxaban and warfarin – taking them with aspirin might cause bleeding problems
  • selective serotonin reuptake inhibitors (SSRIs) such as sertraline, to treat depression
  • medicines for pain and swelling (inflammation) such as ibuprofen and prednisolone
  • medicines to prevent organ rejection after transplant such as ciclosporin and tacrolimus
  • medicines to treat high blood pressure such as furosemide and ramipril
  • digoxin, a medicine for heart problems
  • lithium, a medicine for mental health problems
  • acetazolamide, for glaucoma
  • methotrexate, a medicine used to stop the immune system overreacting and sometimes to treat some types of cancer
  • diabetes medicines, such as insulin and gliclazide

Taking aspirin and other painkillers

It's safe to take aspirin as a painkiller with paracetamol or codeine.

But do not take aspirin with ibuprofen or naproxen without talking to a doctor. Aspirin, ibuprofen and naproxen belong to the same group of medicines called non-steroidal anti-inflammatory drugs (NSAIDs). If you take them together, aspirin and ibuprofen or naproxen may increase the chance of you getting side effects like stomach ache.

Speak to a pharmacist if you're unsure about dosages and timings when taking aspirin with other painkillers.

Mixing aspirin with herbal remedies or supplements

Aspirin may not mix well with complementary and herbal medicines. It could change the way they work and increase your chance of side effects.

Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 05/03/2024 10:26:55