INR home testing for blood thinners
If you are one of nearly a million people in the UK who take an anticoagulant medication, such as warfarin, to make unwanted blood clots less likely to form, you will need regular blood tests to ensure your dose is correct. Blood tests are normally performed at a GP's surgery or anticoagulant clinic, but home testing kits are available for some people.
INR blood tests
If you take too much anticoagulant, your blood won't be clotting enough and you could have problems with bruising or an increased risk of bleeding. But if you take too little there is a risk you could develop a blood clot. This is why it is important to monitor how well you respond to the dose of anticoagulant prescribed for you.
A blood test can measure the effectiveness of your anticoagulant dose. Once the blood is taken, the international normalised ratio (INR) is used to measure how quickly your blood can clot. If necessary, your doctor or nurse will adjust your anticoagulant dose so your INR is within the correct range. When you first start taking an anticoagulant your blood may need testing every other day until the correct dose is established. You won't need testing as often once your INR is stabilised, but you will still need regular testing because your diet, lifestyle and other medications can have an effect on how well the anticoagulant works. On average, people taking warfarin, for example, need their blood checked every 4 to 5 weeks.
People on a long-term anticoagulant will need to attend regular appointments if they have blood tests at their GP's surgery or anticoagulant clinic. These appointments can have an impact on their jobs and travel plans. However, some people can test their INR levels themselves at home or another convenient place by using a portable meter.
INR testing at home
Similar to someone doing blood tests at home to monitor their diabetes, to use a portable INR meter or tester, you will need to prick your fingertip to take a small drop of blood from your finger and put it on a disposable testing strip. The device provides almost instant results after reading the blood on the testing strip. The next step depends on if you are self-testing or self-monitoring:
- Self-testing - You inform your doctor or nurse of the INR reading from the portable meter at an agreed time and they will tell you if you need to adjust your warfarin dose.
- Self-monitoring - After training with your doctor or nurse, you adjust your warfarin dose yourself based on your INR levels. You can use telephone calls, emails, texts or faxes to liaise with your doctor or nurse.
The National Institute for Health and Care Excellence (NICE) and other supporters of INR home testing claim that a person's INR levels are more stable because they can be monitored more regularly, and this puts them at less risk of health complications. They also point out that it is more convenient for both the patient and the NHS. The patient can perform the tests when convenient, without interruption to work patterns or travel plans, and it means fewer appointments for the NHS. For people who prefer home testing and who are able to effectively use a portable device, NICE says the use of 'coagulometers' should be considered for people on long-term anticoagulants who have atrial fibrillation or heart valve disease.
However, INR home testing meters are not available on the NHS, and although test strips can be prescribed their availability on the NHS varies around the UK.