Warfarin safety vital for thousands of Australians

As more and more people rely on warfarin to reduce their risk of developing serious and life-threatening blood clot-related conditions, NPS MedicineWise is supporting people to use the medicine safely and effectively.

For more than half a century, warfarin has been the mainstay of anti-clotting therapy — also known as anticoagulant therapy — for many thousands of Australians. In the ten years from 2000 to 2010, the number of warfarin prescriptions* in Australia rose by 70 per cent — from 1.5 million per year to 2.7 million.

But while warfarin can save lives and prevent disability in people who are at risk of developing harmful blood clots, NPS MedicineWise says education and awareness are vital to help people live safely with warfarin.

“Warfarin is a very effective medicine that has been used for around 60 years to prevent the dangerous blood clots that can cause strokes and other problems,” says clinical advisor Dr Andrew Boyden.

“However, if you take warfarin it is important that you use it safely and correctly, because bleeding is one of its main side effects.”

The INR, or International Normalised Ratio, is the test used to monitor the blood clotting effects of warfarin and make sure people stay within the target range.

“Despite regular testing, many people spend significant periods of time outside of their target range, which can put them at risk of blood clots at one extreme, or serious bleeding at the other,” says Dr Boyden.

Dr Boyden suggests five ways people can be medicinewise with warfarin:

  1. Take your warfarin at the same time every day, and keep taking the same brand. Ask your doctor or pharmacist for advice if you miss a dose.
  2. Have your INR blood tests regularly and don’t skip appointments.
  3. Ask a health professional before starting or stopping any new medicine including vitamins, prescription, over-the-counter, complementary or ‘natural’ medicines.
  4. Let your doctor know about any big changes in your diet or alcohol intake, any illness and travel plans as these can all affect your INR.
  5. Eat about the same amount of foods containing high levels of vitamin K each week as part of your normal diet (e.g. spinach, broccoli, Brussels sprouts).

“There are many factors that can affect how well warfarin works but one of the simplest and most important things you can do is to take your warfarin at the same time every day,” says Dr Boyden.

“It’s also vital to remember that a major change in your lifestyle — including certain food and drinks and other medicines — can affect your INR, which in turn might mean a change to your dose of warfarin.”

“Your health professional will always tell you how much warfarin to take; your dose may be different on different days. Ask your doctor or pharmacist if you are unsure of your dose or which strength of tablet to use, or if you have missed a dose.”

With the launch of a new anticoagulants educational program for health professionals this week, NPS MedicineWise is encouraging people to learn more about living with warfarin by visiting its consumer online knowledge hub at www.nps.org.au/warfarin

For more information about what to do if you miss a dose of warfarin see: www.nps.org.au/warfarinmissdose

*Prescription data is representative of persons who have concessional or RPBS status only. All Pharmaceutical Benefits Scheme (PBS) items for warfarin are below co-payment for general beneficiaries over the time period analysed.


Independent, evidence-based and not-for-profit, NPS MedicineWise enables better decisions about medicines and medical tests. We are funded by the Australian Government Department of Health and Ageing.

Media enquiries: Stephanie Childs on 02 8217 8667, 0419 618 365 or schilds@nps.org.au