The international normalised ratio (INR) blood test tells you how long it takes for your blood to clot.
INR tests are used in people taking warfarin — a medicine that treats and prevents blood clots.
Warfarin is prescribed for some people to:
- prevent stroke if you have atrial fibrillation or other risk factors for stroke
- prevent or treat blood clots (for example, deep vein thrombosis and pulmonary embolism)
- prevent blood clots if you have an artificial heart valve
Your doctor uses your INR results to work out what dose of warfarin you should take. You need to take enough warfarin to reduce your risk of blood clots. But not so much that you are at risk of serious bleeding. This is your ‘target INR range’.
INR Testing and Warfarin Managment FAQ’s
Is an INR test painful?
An INR test is a blood test with specialized testing.
It is no more painful than having a blood test collected.
How often should I have an INR test?
When you first start taking warfarin, your doctor will ask you to have regular INR blood tests. This could be as often as every 1-2 days for the first week.
Once you reach your target INR, and you are taking a consistent warfarin dose, you will still need to have regular INR tests. But you may not need to have them as often.
Do I need to prepare (such as fast or avoid medications) for the sample collection?
No, you do not need to fast for your INR test.
Speak to your regular doctor prior to your test date to discuss possible medication and diet adjustments.