Medication for reducing the risk of stroke in patients with atrial fibrillation

If you have been diagnosed with atrial fibrillation – also known as AF or AFib – you may need treatment to help reduce your risk of a stroke together with medicines and/or procedures to treat your AF or its underlying cause. If this is the case, your doctor (a GP or a cardiologist) may prescribe you a type of medicine known as an oral anticoagulant, often called a ‘blood thinner’.1

Watch a short animation on how to reduce risk of an AF related stroke

AF increases your risk of a stroke as a result of blood clots forming

Anticoagulants do not treat the symptoms of AF. However, if your doctor prescribes an anticoagulant as part of your treatment plan, it is very important that you take it as directed by your healthcare team.1

If you stop taking your anticoagulant medication, your risk of having a stroke may increase

This happens because AF can prevent the heart from pumping blood efficiently around the body, even if you do not have any symptoms.1 The irregular contractions of the upper chambers of your heart (atria) caused by your AF may keep your heart from emptying properly before filling up with blood again. As a result, blood can pool in the upper chambers of the heart and form a thick blob, known as a blood clot.1 If this occurs and a clot – or bits of a clot – break loose, they can travel through the bloodstream towards your brain, blocking one of the arteries leading to your brain.1 Blood carries oxygen – and, if your brain does not receive enough blood because of this blockage, you may have a stroke.1 Blood clots in other parts of your body may also cause problems, but these can also be prevented with an anticoagulant.2

The most common signs and symptoms of a stroke can be recalled with the word FAST

These can be described as1,3

  • Face – your face, mouth or eye may drop on one side, or you may not be able to smile
  • Arms – you may feel weakness or numbness on one side of your body, making it difficult to lift and keep both arms up
  • Speech – your speech may become slurred or you may not be able to talk at all, and you may not understand what others are saying to you
  • Time – it is important to act quickly if you have any of these signs or symptoms

If you, or those around you, notice any of the signs or symptoms above – please call for immediate medical attention!

There are other symptoms, such as sudden problems with vision, confusion, problems with balance and coordination, a very severe and sudden headache, and loss of consciousness, difficulty swallowing, among others.3 However, other conditions may cause these symptoms apart from stroke.3 The symptoms of a stroke may vary from person to person but they usually begin suddenly.3

You should take these symptoms seriously and ask your healthcare team to teach you how to recognise them. It is important that your family and friends are also aware of these symptoms.


Anticoagulants do not actually thin the blood, as the expression ‘blood thinner’ may indicate. However, they do make it harder for blood clots to form, which may help reduce your risk of a stroke.4

Like most medicines, anticoagulants have some side effects

The most common side effect of an anticoagulant is that you bleed more easily, especially if you hurt yourself or fall.1,4 Other side effects include (among others):4

  • Blood in your urine
  • Bloody or black faeces
  • Intense bruising
  • Frequent nosebleeds
  • Bleeding gums, especially after brushing your teeth
  • Heavy periods, if you are a woman
  • Vomiting blood

Reading this list might feel frightening. However, it is important to look at the benefits of reducing the risk of stroke against these side effects. Your risk of bleeding will be assessed by your doctor before you decide together whether an anticoagulant is the most appropriate treatment for you.1 For most people, the benefits of taking an anticoagulant outweigh the risks from the side effects.1,4

Your doctor might offer you warfarin, or other type of oral anticoagulant1

The most commonly prescribed anticoagulant is warfarin – however, there are other types of anticoagulants.1,4

These medications are usually taken orally as a tablet or as a liquid.1,4 Your healthcare team will tell you how to take these medications and for how long.

You will need to have a regular blood test called international normalised ratio, also known as INR – especially over the first few weeks or months of your treatment.1,5 This test will help your doctor decide which dose of warfarin is appropriate for you.1,5

Your warfarin treatment is meant to help your blood flow through your veins more easily, making blood clots less likely to form. However, it should not keep your blood from clotting completely, as this may increase your risk of bleeding more easily.5 The INR test measures the time it takes for your blood to clot. If the time it takes for your blood to clot is too long, your INR will be high. This means that your current dose of warfarin has increased your risk of bleeding. As a result, your doctor will decrease the dose.1,5 In this way, the INR test will help your doctor find the dose of warfarin that is appropriate for you, so that it helps your blood flow easily but does not keep it from clotting completely.5

You should ask your healthcare team for advice on your diet while on anticoagulants.

While you are on warfarin, you also need to be mindful of your diet. Some foods can interfere with how warfarin works in your body.1,5 Because of this, you should ask your healthcare team for advice on your diet while on warfarin and always talk to them before you change your usual diet suddenly.1,5

You will not need to have a regular INR test and you are less likely to have dietary restrictions. For this reason, these medicines have become more popular. However, you may still need to take certain precautions when on other anticoagulants, such as taking your medicine with food or at certain times of day, depending on the medicine that you have been prescribed.6 It is important that you ask your doctor what the benefits and risks are for each medication.1

There are some additional precautions that you should take when on an anticoagulant

Ensure that you tell everyone in your healthcare team – including your dentist, pharmacist, and nurse – that you are taking an anticoagulant, and before you take any other medications – including prescription and over-the-counter medications – ask a pharmacist to confirm that there are no interactions between them.1,4

All anticoagulants may help reduce your risk of a stroke, but with several options available, it is important to discuss your treatment with your doctor.1 Continue to take your medications as prescribed, unless your doctor tells you to stop.1

1. Stroke Association. Atrial fibrillation (AF) and stroke. May 2019. Available at Last accessed November 2020. 

2. WebMD. Atrial Fibrillation and Blood Clots. Available at:,left%20part%2C%20of%20your%20heart. Last accessed May 2021.

3. NHS. Stroke − Symptoms. August 2019. Available at Last accessed November 2020.

4. NHS. Overview. Anticoagulant medicines. May 2018. Available at Last accessed November 2020.

5. NHS. Warfarin. April 2019. Available at Last accessed November 2020.

6. Lane DA et al. Circulation. 2015; 131: e412 – e415

PP-ELI-HKG-0649 JUN 2021