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Yvonne Wren

Yvonne Wren

“I can regularly see what my INR is and adjust my warfarin dose accordingly. This has been totally liberating!”

INR and self-testing

Most APS patients will be on life-long anticoagulation and, for those who have had a serious clotting event, the current treatment usually takes the form of warfarin.


Warfarin is a powerful anticoagulant that interferes with your blood clotting process in order to prevent blood clots from forming. It has been used as a medicine since 1954 and is considered to be a fairly safe and stable drug.


INR is an acronym for the International Normalised Ratio and is a test which measures the length of time it takes your blood to clot compared to normal; normal blood has an INR of approximately 1.0. The INR test was developed by the World Health Organisation so that tests would be standard throughout the world, allowing people who have to take life-long warfarin to travel and get comparable blood tests wherever they are.

INR range

Each patient has a target INR which is set by a consultant according to their condition or disease and medical history. The dosage of warfarin can vary widely from person to person, some patients only need 4mg a day while others may need 18mg or more; therefore, when you first start treatment, the warfarin dose will be adjusted up or down to achieve your target INR. The strength of warfarin tablets is clearly marked by the colour and number stamped on them. If the INR is too low then the dosage is increased; if the INR is too high then the dosage is decreased.

INR monitoring

Everyone taking warfarin will have their INR monitored through regular blood tests either by a venous sample or finger prick test carried out in their GP's surgery or anticoagulation clinic.

Patient self-testing

Self-monitoring can be particularly useful for people with busy lives who have work/family commitments, for those who find it difficult to travel to clinics due to distance or disabilities, for overseas travellers and, of course, people who have highly unstable INRs.

Points to consider before buying a self-testing machine

Self-monitoring is not for everyone, but it can give you a better quality of life and lets you play an active role in your own health care.

Will the INR results be the same?

It is now widely accepted that finger-prick testing is just as accurate as venous tests with many surgeries now opting for finger-prick testing as standard.

Is it safe for APS patients to self-test?

Due to the instability of INR levels in APS patients, self-testing is often a sensible approach both in terms of looking after your health and managing your quality of life. It allows you to test immediately if you are feeling unwell, and also means you can get on with your life with fewer visits to the anticoagulation clinic.

What to do if you are positive for the Lupus Anticoagulant

First of all find out whether you tested positive for the lupus anticoagulant – you will be able to find this information from either your GP or consultant.

How do I start self monitoring?

Go through the list of points to consider before buying a self-testing machine.

INR and self testing fact sheet

Download and keep our complete guide to INR and self testing.

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