Blood-thinning medicines Rongoā whakakōrahirahi i te toto
Blood-thinning medicines (also called anticoagulants) are used to prevent or treat blood clots. They do not actually thin your blood, rather they disrupt the process of your blood clotting.
What blood-thinning medicines do
Blood clots are made up of:
- red blood cells
- platelets (tiny cell fragments)
- blood proteins (including fibrin, which acts as a glue).
Blood-thinning medicines (also called blood thinners) reduce how well these blood proteins work, so your blood does not clot so easily.
Blood-thinning medicines are used to treat and prevent:
- deep vein thrombosis or DVT (a clot in your vein)
- pulmonary embolism or PE (a clot in your lungs).
They are also used to stop blood clots forming in your heart, which can cause a stroke if you have:
Using blood-thinning medicines
How long you will need to take blood-thinning medicines depends on the medical condition being treated and your other risk factors. You may need to stay on them for life.
All medicines have some risks. If you take anticoagulants, you may bruise and bleed more easily because it takes longer for your blood to clot. It is possible you could have serious bleeding in your bowel or even your brain, which could cause a stroke.
Your healthcare provider can talk with you about the benefits and risks of blood-thinning medicines.
Do not take anti-inflammatory tablets such as ibuprofen (for example, Nurofen), diclofenac (for example, Voltaren) or naproxen (for example, Naprosyn) if you are using blood-thinning medicines, as they increase your risk of bleeding.
Many over-the-counter health supplements can also raise your risk of bleeding, including:
- garlic
- fish oil
- ginkgo biloba.
Another product, St John’s wort, may make your blood-thinning medicine less effective.
If you are taking a blood-thinning medicine, check with your healthcare provider or pharmacist before taking an over-the-counter health supplement.
Types of blood-thinning medicines
Anticoagulant injections such as enoxaparin (Clexane) are used in hospital to prevent clots, for example, when you are having major surgery. Sometimes you will have these for a few days at home when starting treatment.
Enoxaparin — My Medicinesexternal link
There are 2 types of anticoagulant tablets:
- warfarin
- novel oral anticoagulants (NOACs).
The kind you are given will depend on the reason you need blood thinners and your other medical conditions.
Warfarin
Warfarin has been used as a blood thinner for a long time. It stops blood clotting by reducing vitamin K, which your body needs to form clots.
Warfarin — My Medicinesexternal link
If you are taking warfarin, you will need a regular blood test (called an INR) to check that your dose is still correct.
- If your warfarin dose is too high, you may have bleeding problems.
- If your warfarin dose is too low, it may not work.
Certain food types can either increase or decrease the effect of warfarin. You will need to try not to make big changes to the way you eat.
Food choices when you are taking warfarin
Other medicines you take can also affect warfarin levels.
There is an antidote or reversal medicine for warfarin if you have severe bleeding.
How does warfarin work? — British Heart Foundation YouTubeexternal link
Warfarin monitoring with INR tests
If you are taking warfarin, it is important you have a regular blood test (INR) to get your dose of warfarin correct. The INR test checks how long it takes your blood to clot.
The INR test result should usually be between 2 and 3, depending on the condition you are being treated for.
You can get your INR test at:
- your healthcare provider
- a blood collection centre (community laboratory)
- some community pharmacies (using a finger-prick test instead of blood collection).
After each test, your healthcare provider or pharmacist will tell you what warfarin dose to take and when to have your next test.
You may need extra tests if you start taking another medication or become unwell.
Ask your healthcare provider or pharmacy about booklets and calendars to help you record and remember your tests and warfarin doses. There are also apps you can use to keep this information.
Food choices while you are taking warfarin
There is no special diet to follow if you are taking warfarin. But there are certain foods and drinks that can affect how your warfarin works.
It is important to talk to your healthcare provider:
- before making any major changes to your diet
- if you cannot eat for several days or you have an ongoing stomach upset, diarrhoea or fever.
Vitamin K has the opposite effect to warfarin and may cause your blood to clot more quickly.
It is found in some foods and nutrition supplements.
If you take warfarin, keep eating foods that are rich in vitamin K but try to eat the same amounts every day. Warfarin works best if you avoid suddenly eating a lot more or a lot less vitamin K-rich foods.
Foods rich in vitamin K-rich include:
- brussels sprouts
- celery
- chinese cabbage — bok choy, choy sum, tatsoi
- dark green lettuce
- endive
- kale
- mesclun salad leaves
- puha
- silverbeet
- spinach
- watercress.
Aim to have at least 5 servings of vegetables every day:
- Have a dark green leafy vegetable as one of these.
- One serving of vegetables equals a handful.
- Some herbs, such as parsley and basil are also high in vitamin K. But we usually eat these in small amounts so they should not affect how your warfarin works.
These oils contain small amounts of vitamin K.
- Use them in small amounts in cooking.
- Limit fried foods, mayonnaise, salad dressings and other products that could contain these oils.
Drinking too much alcohol can affect how your warfarin works. If you drink alcohol, limit it to:
- Women — 2 standard drinks a day with no more than 10 drinks a week.
- Men — 3 standard drinks a day with no more than 15 drinks a week.
Having too much cranberry juice, grapefruit juice or green tea can affect the way warfarin works. Limit yourself to a total of no more than one cup (250 ml) of these drinks per day.
Talk to your pharmacist or healthcare provider if you take warfarin and want to take cranberry supplements.
Talk to your healthcare provider before starting or stopping any nutrition supplements or herbal medicines.
Many nutrition supplements contain vitamin K, such as:
- vitamins
- minerals
- dried or powdered vegetable supplements (like Super Greens or Super Foods).
Some do not, but they may still affect the way warfarin works.
Novel oral anticoagulants (NOACs)
There are newer types of blood thinner, such as dabigatran (Pradaxa) and rivaroxaban (Xarelto). These work by blocking proteins in your blood needed to make clots.
Dabigatran — My Medicinesexternal link
Rivaroxaban — My Medicinesexternal link
You do not need regular blood tests to check the dose of these medicines. They are also less affected by other medicines and foods.
They are not suitable for all conditions that need blood thinners.
There is an antidote or reversal medicine if you have severe bleeding.
How do novel oral anticoagulants (NOACs) work? — British Heart Foundation YouTubeexternal link