There is a blood test known as a prothrombin time test (PT), which measures the amount of time for blood to clot. PT is known as the International Normalized Ratio (INR). The INR is calculated from the findings of a PT test and used to monitor individuals who are prescribed the anticoagulant medication warfarin.
Typically, people go to a clinic or a health care provider to do this test. However, it is possible to take the test at home. Before doing the INR at home, you should consult with your health care provider about the numbers and test results you should get and when or how to contact them if you have any problems. Read all instructions about your INR test meter that are provided in its box. You can also contact the manufacturer if you have questions with the toll-free phone number provided in the instructions. If you want to learn more about INR testing, check out our article about INR testing at home.
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Read the instructions that come with an INR test meter and lancet and follow them strictly. Here are some tips to get your blood sample:
To understand how often you need to do the test, you can contact your health care provider and follow their recommendations. It is typically recommended to perform the test every 1 to 4 weeks. Consult with your health care provider if you want to make any changes to your medications because any change may affect your warfarin dose or monitoring schedule.
Certain foods like leafy green vegetables and some herbal supplements can influence your body’s response to warfarin. Therefore, you need to tell your health care provider if you are about to change your general health or diet.
Like any other medical test, there are risks to monitoring warfarin at home with an INR test meter. When taking warfarin, seek medical attention immediately in the following situations:
When a doctor prescribes you an INR test meter, your health care provider will identify the appropriate INR range for you. Contact your health care provider if you get an INR result outside of your specified INR range.
An INR result higher than 4.5 is less reliable than a result less than 4.5. Therefore, in the case of an INR result higher than 4.5, you may be requested to have your blood drawn and tested by a laboratory to confirm the accuracy of your INR test result and your warfarin dosage.
There are certain changes in your usual routine, such as illness or an increase in the intake of leafy green vegetables, that can result in a change in your INR test results. An INR test meter can provide inaccurate results due to a number of factors. These may include:
Every meter has its own different technology to generate results. Contact your health care provider before starting to use the meter. Learn about health conditions and other factors that affect how an INR meter works. For example, the following common situations may affect some meters:
Meters have user manuals with instructions and warnings in them. Read the manual, so you can understand how to use the INR meter properly.
There are a few more things to consider before moving on to home testing:
Patients, especially seniors, who can’t go to the lab regularly, travel frequently, have trouble leaving their homes, or wish to be more independent can choose in-home testing. Whatever your rationale for transitioning to home testing, the important thing is that you continue to test your levels.
When a patient expresses a desire for in-home testing, the reason for their anticoagulation must be considered. Some blood illnesses, such as antiphospholipid syndrome (APLS), interfere with how the system evaluates INR ratings. Therefore, point-of-care testing is preferred not to be conducted on those individuals.
To ensure the proper function of the INR meter, you can use different ways:
The FDA has many regulations related to taking an INR test. Fortunately, patients do not need to visit their health care provider’s clinic every time they want to test their INR. You can perform your test at home using an individual INR test meter. Keep in mind that there are risks in doing this test at home. Patients must be aware of the risks and other factors which can alter the test results. It is recommended to talk to your health care provider before you start taking the test.
If you have used INR test meters at home, please tell us about your experience.