What are blood thinners?

Blood thinners include anticoagulants and antiplatelet agents. They are medicines used to help prevent blood clots from forming.

Doctors also use anticoagulants to treat blood clots that have formed in your body due to conditions such as:

• heart attack
• stroke
• deep vein thrombosis (DVT)
• pulmonary embolism (PE)

These medicines can be used to help prevent heart attacks and strokes by keeping clots from forming in the arteries that bring blood and oxygen to your heart and brain.

You may be prescribed blood thinners if you have:

• had a stroke or heart attack
• an abnormal heart rhythm
• angina
• had a procedure on your heart, like a stent or a procedure for heart valve disease

When you have some types of surgery, like hip or knee replacement, blood thinners can help stop clots from forming while you heal. Your doctor will weigh up your need to stop clots against your chance of bleeding during and after surgery.

How do blood thinners work?

Different types of blood thinners work in different ways:

• Anticoagulants work by stopping the production of clotting factors (these are substances in your blood and are needed for normal blood clotting).
• Antiplatelet medicines stop small blood cells (called platelets) from sticking together and making a blood clot.

When your doctor prescribes a blood thinner, they will consider many factors to decide which option is best for your situation, for example, if you:

• are pregnant
• are older
• have problems with your kidneys or liver
• have a low platelet count or other bleeding problems
• are at risk of falling
• have very high blood pressure
• need major surgery

What types of blood thinners might I be given or prescribed?

You may be prescribed anticoagulant medicines or antiplatelet medicines.

Anticoagulant medicines

The 2 main types of anticoagulant medicines you might take by mouth are:

• DOACs (direct acting oral anticoagulants) — these include dabigatran, apixaban and rivaroxaban. DOACs used to be called NOACs (non-vitamin K antagonist oral anticoagulants).
• warfarin

Some anticoagulants are given by injection, for example heparin, enoxaparin or dalteparin. These are often started in the hospital. Some people need to continue using enoxaparin or dalteparin when they go home.

Antiplatelet medicines

Some common antiplatelet medicines include:

• aspirin
• clopidogrel
• a combination of aspirin and dipyridamole

Other antiplatelet medicines that may be prescribed are prasugrel and ticagrelor.

Aspirin can be bought over the counter in Australia. Check with your doctor what dose to take. Other blood thinners need a prescription from your doctor.

What are the side effects or risks of blood thinners?

The most serious possible side effect of blood thinners is the risk of heavy bleeding. You might bleed from different parts of your body, especially if you take more medicine than your doctor has prescribed.

Some signs of bleeding include:

• bruising, bleeding gums or nose bleeds
• red or brown urine (wee)
• red or black stools (poo)
• coughing up blood or blood in vomit
• heavier than usual menstrual periods
• severe headache or dizziness

Other side effects include:

• nausea
• diarrhoea or constipation
• headache
• fever
• cough

How do I take blood thinners?

Here are some important things to remember when you take blood thinners:

• Take blood thinners exactly as your doctor prescribes.
• Take the tablets whole with a glass of water unless your doctor or pharmacist tells you something different.
• Take the medicine for as long as your doctor prescribes them.
• Don't stop taking it or change the way you take it without talking to your doctor first.

If you forget a dose, ask your doctor or pharmacist what to do. Do not take a double dose to make up for the missed dose. If you take too much blood thinner, talk to your doctor right away.

Warfarin

If you are taking warfarin, you will need to have regular blood tests to check how fast your blood is clotting.

You also need to be careful about your diet when taking warfarin.

• Avoid grapefruit and cranberry juice, and drink no more than 1 or 2 standard alcoholic drinks per day.
• Try to eat the same types of food regularly, especially those high in Vitamin K, like green leafy vegetables and those from the cabbage family.

Drug interactions

Blood thinners can interact with many different medicines, including ones you buy over the counter at a pharmacy, vitamins, and herbal or complementary medicines. A drug interaction is when one of your medicines changes how another medicine works. Always talk to your doctor or pharmacist before you take any new medicine.

Medical procedures and operations

If you take a blood thinner and need to have a medical procedure or operation, your doctor may ask you to stop your blood thinner for a short time around the time of your procedure.

Your doctor will decide if you should stop taking your blood thinner. This decision depends on the type of blood thinner you take, your medical history, and the type of procedure or surgery you will have.

You should also let your dentist know which medicine you are taking.

Tattoos or body piercing

If you take a blood thinner, getting a tattoo or body piercing could cause severe bruising. Before getting a tattoo or body piercing, ask your doctor if it's safe to stop your blood thinner for a short time. Don't stop taking it or change the way you take it without talking to your doctor first.

When should I see my doctor?

You should see your doctor if you have any signs of bleeding or signs of an allergic reaction to the medicine.

You should call your doctor straight away or visit your nearest emergency department if you have any of the following symptoms:

• coughing up blood
• vomiting, and it is black
• black stools (poo) or blood in your poo
• red or brown urine
• bleeding that doesn't stop or lasts a long time

If you need surgery or a medical or dental procedure, let your healthcare team know that you are taking blood thinners when you book the appointment.

Are there any alternatives to this medicine?

There aren't any alternatives to taking blood thinners.

There are, however, other things you can do to reduce your risk of a heart attack or stroke. These include:

• healthy eating
• exercise
• quitting smoking
• taking medicines to reduce high cholesterol and blood pressure

Resources and support

For more information on blood thinners, who should take them and how they work, visit the Heart Foundation or Stroke Foundation websites.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.