Aspirin to prevent blood clots

About aspirin to prevent blood clots

How does low-dose aspirin work?

Aspirin works by making platelets in the blood less sticky. Platelets help stop bleeding, but sometimes they can clump together inside a blood vessel and form a clot. This can block blood flow and cause a heart attack or stroke.

Low-dose aspirin (75 mg) helps stop platelets from sticking together, which reduces the risk of blood clots. It is often used for people with heart or blood vessel disease, or those who have had a heart attack, stroke, or heart surgery.

Low-dose aspirin is available with or without a prescription, but you should only take it regularly if your doctor recommends it, as it isn’t suitable for everyone.

At higher doses, aspirin is used to relieve pain and high temperature (fever). There is more information about this use of aspirin in a leaflet called Aspirin for pain or fever.

Side effects of low-dose aspirin

Common side effects of aspirin are:

• Feeling sick (nausea).

• Indigestion.

• Stomach pain.

• Bleeding more easily (such as nosebleeds or bruising).

You will find a full list in the manufacturer's information leaflet supplied with your medicine.

How to manage low-dose aspirin side effects

The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

If you experience any other symptoms which you think may be due to the tablets, speak with your doctor or pharmacist for further advice.

Who should not take low-dose aspirin?

Some medicines aren’t suitable for everyone. Before taking aspirin to prevent blood clots, it’s important your doctor knows:

• If you are pregnant or breastfeeding.

• If you have ever had a stomach ulcer.

• If you have asthma.

• If you are under 16 years of age.

• If you have any problems with the way your liver works or with the way your kidneys work.

• If you have a blood disorder such as haemophilia, or glucose-6-phosphate dehydrogenase (G6PD) deficiency.

• If you have gout.

• If you have high blood pressure (hypertension).

• If you have ever had an unusual or allergic-type reaction after taking aspirin or a non-steroidal anti-inflammatory drug (NSAID).

  • NSAIDs include ibuprofen, diclofenac, indometacin and naproxen. You should also let your doctor know if you have ever had an allergic reaction to any other medicine.

• If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

How to take low-dose aspirin

• Before taking aspirin, read the leaflet inside the pack for important information and possible side effects.

• You will usually be advised to take one 75 mg tablet once a day, unless your doctor tells you differently. Take it exactly as prescribed.

• Take aspirin at the same time each day to help you remember. Many people take it in the morning with breakfast.

• Check what type of aspirin you have:

  • Dispersible tablets should be mixed with water and taken with food to protect your stomach.

  • Gastro-resistant (enteric-coated) tablets can be taken without food. Swallow them whole with water and do not chew them.

• If you are taking gastro-resistant tablets, do not take indigestion remedies in the 2 hours before or after your dose.

• If you miss a dose, take it when you remember unless it’s the next day. Do not take two doses at once.

Getting the most from your treatment

• Keep all your regular appointments with your doctor. This is so your doctor can check on your progress.

• Before taking any over-the-counter medicines, ask your pharmacist if they are safe with aspirin.

• Do not take other medicines that contain aspirin or anti-inflammatory painkillers such as ibuprofen, including many cold and flu remedies.

• Aspirin should not be given to children under 16 unless prescribed, because it may be linked to Reye’s syndrome, a very rare but serious illness.

• If you are due to have an operation or dental treatment, tell the person carrying out the treatment that you are taking aspirin. This is because any bleeding may take longer than normal to stop.

• If a child accidentally takes aspirin, go to A&E immediately. Take the medicine packaging with you, even if it is empty.

How to store low-dose aspirin

• Keep all medicines out of the reach and sight of children.

• Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Frequently asked questions

How long does it take for aspirin to prevent blood clots?

Aspirin starts to reduce platelet stickiness within about 1 hour of taking a dose. However, its full protective effect against blood clots is usually reached after several days of taking it daily.

Is it safe to take aspirin as a blood thinner long-term?

Yes, low-dose aspirin can be taken long-term as a blood thinner, but only under a doctor’s supervision. Long-term use can increase the risk of stomach irritation, ulcers, or bleeding, so your doctor will weigh the benefits against the risks and may recommend stomach protection if needed.

Can anyone take aspirin to prevent blood clots?

No, not everyone should take aspirin to prevent blood clots. It is only recommended for people with heart or blood vessel problems, a history of heart attack or stroke, or high clot risk, and should never be taken by children under 16 or anyone without a doctor’s advice