What is Warfarin?

Warfarin is an ‘anticoagulant’, which is a medication which prevents your blood from clotting, commonly called ‘blood-thinners’. Warfarin does this by blocking vitamin K, which is a vitamin which helps create a lot of the proteins which help the blood clot.

Why do I need Warfarin?

Warfarin can be used to prevent blood clots from forming or to prevent already formed clots from growing larger. These blood clots can lead to serious problems like strokes or pulmonary emboli (clots on the lung). Your doctor may want you to be on warfarin because you have a condition which makes blood clots more likely, for example an irregular heartbeat like Atrial Fibrillation.

Are there risks associated with Warfarin?

All medications have risks associated with them. The main risk you should be aware of with warfarin is the potential for serious internal bleeding, because it stops the normal clotting process. This bleeding can lead to hospitalisation, serious disability and even death. To avoid this, it is important to monitor your warfarin levels.


Everybody responds differently to warfarin, and so it is important to measure the effect warfarin is having on your body and make sure you are on the right dose. This is done by checking your International Normalized Ratio (INR), which can be tested with a simple fingerprick blood test. This is important to make sure the medication is stopping your blood from clotting, but not too much that you are at risk of serious bleeds. At first, this testing will need to be done every second day, but once your levels normalize, they are usually done once every few weeks.

What else should I be aware of?

Lots of medications can interact with warfarin, so it is important that your doctor is aware of what medication you take while you are on warfarin (even over-the-counter medications) as your dose may need to be adjusted. Some foods (eg grapefruit) can also interact, as well as alcohol.

As vitamin K comes mainly from fruit and vegetables (especially green leafy vegetables), it is important to eat a fairly consistent amount of these foods. If your intake of these foods is not stable, you may find that your INR begins to fluctuate also.

If you are interested in learning more about this topic, feel free to book an appointment with one of our friendly doctors by booking online or contacting us by phone on 8269 6000.


American Heart Associaton 2018, A Patient’s Guide to Taking Warfarin [ONLINE] Available at: http://www.heart.org/HEARTORG/Conditions/Arrhythmia/PreventionTreatmentofArrhythmia/A-Patients-Guide-to-Taking-Warfarin_UCM_444996_Article.jsp#.WsTR0tNua34. [Accessed 04 April 2018]

Melbourne Haematology 2018, Warfarin | Fact Sheets [ONLINE] Available at: http://www.melbournehaematology.com.au/fact-sheets/warfarin.html. [Accessed 04 April 2018]

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