There are two main types of blood-thinning medication:
- Antiplatelets.
- Anticoagulants.
Both types reduce the risk of clots in your blood vessels, but they work in different ways.
Which blood-thinning medication will I be given?
Antiplatelet medication is often the first blood-thinner used after a transient ischaemic attack (TIA or mini-stroke) or ischaemic stroke. This could include aspirin, clopidogrel and sometimes ticagrelor. Later, you might change to anticoagulants or stay on antiplatelets. Some people will start on anticoagulants straight away. A healthcare professional can discuss with you which medication is best for you.
You should have a check-up at least once a year to make sure the medication is working and check your other stroke risk factors. You will need more frequent checks if you’re on some types of anticoagulant.
This page can only give general information. You should always get individual advice about your own health, medication and treatment from a medical professional, such as a GP or pharmacist.
Always take your medication exactly as prescribed by your doctor and check with them if you have any questions about your medication.
Possible side effects of blood-thinning medication
Like all medications, blood-thinning medications may sometimes cause side effects. This includes an increased risk of bleeding.
Side effects may be mild or more serious. While not everyone will get side effects, it’s important to be aware of them.
Serious side-effects
- If you have any stroke symptoms, always call 999 immediately.
- Contact your GP immediately or go to your nearest accident and emergency (A+E) department if you have:
- Blood in your wee, poo or vomit.
- Severe bruising.
- Prolonged nosebleeds.
- Chest pain.
- Wheezing or difficulty breathing.
- Sudden, severe back pain.
- Had a blow to your head.
Other side-effects
These vary between types of medication, but the most common include:
- Indigestion.
- Diarrhoea, constipation, feeling sick or being sick.
- Itchy skin.
- Headaches.
Do not stop taking your medication if you have side effects, as this can increase your risk of a stroke. Do contact your GP, pharmacist or call 111 for advice.
You can report side effects using the Yellow Card scheme.
Tip: Read the patient information leaflet that comes with your medication for a full list of possible side effects.
Antiplatelets
How do antiplatelets work?
Platelets are small, sticky cells in your blood. They are an important part of the clotting process because they can clump together at the site of a wound, such as a cut on your skin. This protects the wound and stops bleeding. But if platelets clump together inside an artery and form a clot, it can travel to the brain and cause a stroke.
Antiplatelet medications make it harder for the platelets to stick together, so that a clot is less likely to form.
When they are used
Antiplatelet treatment is often used after a stroke or TIA if you have atherosclerosis, which means having a build-up of fatty material inside your arteries.
Types of antiplatelet
You may know aspirin as a painkiller, but it is also prescribed at a low dose to reduce blood clotting.
Who can and cannot take aspirin
Pregnant women may be prescribed low-dose aspirin if they have a risk of blood clots or stroke. Aspirin can pass into breast milk in very small amounts, so get advice from your midwife, pharmacist or GP if you’re breastfeeding.
Aspirin may not be suitable for some people, including those with:
- Liver or kidney problems.
- Asthma.
- A blood-clotting disorder.
- Allergy to other nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen.
How to take aspirin
It’s important to take aspirin exactly as your doctor has told you.
It’s usually taken once a day. Taking aspirin with food can reduce stomach upsets. Do not take extra aspirin as a painkiller, as this can cause bleeding. Speak to a pharmacist for advice about alternative painkillers.
Possible side effects of aspirin
As well as the side effects previously mentioned, some other serious side effects may include:
- Painful joints in hands and feet can be a sign of high levels of uric acid in the blood.
- Skin or eyes turning yellow, or wee turning darker, can be signs of liver problems.
- Swollen hands or feet can be a sign of water retention.
Seek medical help right away if you experience of any of these.
Clopidogrel is an antiplatelet often used with, or instead of, aspirin.
Who can and cannot take clopidrogel
If you’re pregnant or breastfeeding you might not be able to use clopidogrel, but it can be used if necessary. A doctor will discuss the options with you.
Clopidogrel may not be suitable for people with:
- Liver or kidney problems.
- Blood-clotting disorders.
- Stomach ulcers.
For some people with certain gene variations, clopidogrel may be less effective and you may be offered testing just after a stroke to see if an alternative antiplatelet may be more suitable for you.
Some proton pump inhibitor (PPI) medications, which are used for acid reflux (heartburn), can make clopidogrel less effective. Speak to your doctor who may prescribe an alternative PPI.
How to take clopidogrel
It’s important to take clopidogrel exactly as your doctor has told you. It’s usually taken once a day, at the same time each day. It can be taken with or without food.
Possible side effects of clopidogrel
As well as the side effects previously mentioned, some other serious side effects may include:
- Skin or eyes turning yellow.
- Feeling very tired or having signs of infection, such as fever or sore throat.
Seek medical help right away if you experience of any of these.
Dipyridamole is a less commonly prescribed antiplatelet. If your doctor recommends using it, they will discuss your treatment options.
Anticoagulants
How do anticoagulants work?
There are several different types of anticoagulants which work at different stages of the clotting process. Although they work in slightly different ways, they all reduce the risk of clot formation.
When are anticoagulants used?
Anticoagulants are often used for people with heart conditions like atrial fibrillation or a metal heart valve replacement.
Who can and cannot take anticoagulants?
Many anticoagulants are not recommended while you’re pregnant or breastfeeding. If you are pregnant or planning to have a baby, speak to your GP or midwife. You’ll need help to manage your risk of a stroke or blood clots while pregnant. This may include having an injectable anticoagulant, such as heparin. Your GP or midwife can also give advice about your medication if you’re breastfeeding.
You might not be able to take some types of anticoagulant, or you may need a reduced dose, if you have certain conditions, for example:
- Liver or kidney problems.
- Thyroid problems.
- Blood-clotting disorders.
- Stomach ulcers.
Your doctor will discuss your options with you and the benefits and risks. You should then decide together which anticoagulant would be most suitable for you.
Monitoring and check-ups while you're on anticoagulants
Direct oral anticoagulants (DOAC)
The most common type of anticoagulants are DOACs. There are several types of DOAC, including apixaban, dabigatran, rivaroxaban and edoxaban.
Before starting on a DOAC, you will have blood tests to check for problems such as liver, kidney and blood clotting disorders. Once you are taking them, you will have a follow-up check at one month. After that, checks could be around three to six months apart depending on your age and health.
The check-up looks at side effects including bleeding, and any help you need with taking your medication. You should have an annual kidney and liver function blood test.
Warfarin
Warfarin needs more monitoring than DOACs, but is still the best treatment for certain conditions. For more details of how warfarin is monitored, see the Warfarin section below.
Types of anticoagulant
How it works
Apixaban makes the blood less likely to clot by blocking a protein (Factor Xa) in the blood. You will not need to have regular blood tests.
How to take it
It’s important to take apixaban exactly as your doctor has told you. Try to take apixaban at a regular time of day. It’s usually taken twice a day, with or without food.
Possible side effects of apixaban
As well as the side effects previously mentioned, some other side effects may include:
- Anaemia (a problem with blood cells).
- A mild rash.
How it works
Dabigatran etexilate attaches itself to a protein (called thrombin) in your blood, making your blood less likely to form a clot.
How to take it
It’s important to take dabigatran exactly as your doctor has told you. Try to take dabigatran at a regular time of day. It’s usually taken twice a day, with or without food.
Possible side effects of dabigatran
As well as the side effects previously mentioned, some other side effects may include:
- Stomach pain, indigestion or feeling sick (nausea).
- Anaemia.
How it works
Rivaroxaban makes the blood less likely to clot by blocking a protein (Factor Xa) in the blood. This protein plays a key role in the blood clotting process.
How to take it
It’s important to take rivaroxaban exactly as your doctor has told you. Try to take rivaroxaban at a regular time of day. It’s usually taken once or twice a day. It’s best taken just after a meal or snack to help your body absorb it.
Possible side effects of rivaroxaban
As well as the side effects previously mentioned, some other side effects may include:
- Dizziness.
- Mild rash.
- Anaemia.
How it works
Edoxaban, like apixaban and rivaroxaban, makes the blood less likely to clot by blocking a blood protein called factor Xa. You will not need to have regular blood tests.
How to take it
It’s important to take edoxaban exactly as your doctor has told you. Try to take edoxaban at a regular time of day. It’s usually taken once a day, either with or without food.
Possible side effects of edoxaban
As well as the side effects previously mentioned, some other side effects may include:
- Itchiness.
- Nausea or stomach pain.
- Anaemia.
Warfarin blocks the liver from using vitamin K to make ‘clotting factors’. Clotting factors are needed in the process of forming clots. So warfarin makes your blood less likely to clot.
How to take warfarin
It’s important to take warfarin exactly as your doctor has told you. Try to take warfarin at a regular time of day. It’s often taken in the evening. It’s usually taken once a day, either with or without food.
Before starting warfarin, you will have tests to check for problems such as liver, kidney, blood clotting and thyroid disorders.
While taking warfarin, you have regular blood tests to measure how long your blood takes to clot. This is called the international normalised ratio (INR). At the start, you may have daily tests and your dose is adjusted until the target INR is met. Tests reduce to once or twice weekly until your INR is stable. After that, tests can be around 12 weeks apart, but some people need more frequent checks.
Ask your GP if you might be able to use a self-testing kit at home.
Food and drink that can affect warfarin
It’s important to keep your diet fairly steady over time if you’re taking warfarin. Speak to your GP or pharmacist before changing your diet, as this may affect how warfarin works.
Vitamin K can interfere with warfarin. It’s found in foods such as green leafy vegetables like spinach and broccoli, avocados and vegetable oils. You can still include these foods in your diet, but talk to a healthcare professional for advice.
Drinking grapefruit, cranberry or pomegranate juice, or large amounts of alcohol, can raise the risk of bleeding on warfarin and should be avoided.
Possible side effects of warfarin
The main side effect of warfarin is an increased risk of bleeding. Less common side effects may include rashes or hair loss.
