How do I know if the warfarin is working? You will not be able to tell if your warfarin is working by how you feel. You will not feel any different. The amount of medicine needed to prevent blood clots varies from person to person.
You need regular blood tests to see if your warfarin is working. This test is called an INR. The INR tells how well the warfarin is working. The INR is used to tell how much warfarin you need. It is important for you to know your INR results. Your INR result will be used to adjust your warfarin dose.
Your INR result can change for many reasons. You must take your warfarin as told to avoid serious problems caused by either low or high INRs that can sometimes lead to death. Problems with INRs that are too high include bleeding. Problems with INRs that are too low include blood clots.
The INR is the usual test used to see if your warfarin is working. Some care providers may refer to this test as a protime, prothrombin time, or PT.
What is an INR blood test? The INR (International Normalized Ratio) measures the time it takes for your blood to clot.
How is an INR done? This test is done by taking blood from a vein or from a fingertip. It does not matter what time of day your test is done. However, it is best to get the test done early in the day so results are ready before it is time for you to take your next dose of medicine. Your warfarin dose may be adjusted based on your test result.
What should my INR result be? People who are not on warfarin should have an INR result of about 1. If you are on warfarin, your INR result should usually be between 2 and 3 (this is called a range). Your health care provider may want a higher or lower range depending on why you are on warfarin. Your health care provider should tell you what your range is for your blood test results. This range will be your INR goal. If you are not given this information, you should ask for it. It is important for you to know. You can help your provider give you the best care if you do these things:
What does my INR mean? If your INR gets too high, it is taking too long for your blood to clot. This raises your chance of bleeding. If your INR is too low, your blood clots quickly and raises your chance of a blood clot. Stay in touch with your health care provider and work together to keep your INR within your INR goal range.
What should I do if my INR is higher or lower than my INR goal? Call the health care provider that manages your warfarin. Your dose may need to be adjusted.
How often do I need to get my INR checked? Tests will be scheduled on a regular basis as long as you are on warfarin. How often you need blood tests will depend on:
Why you are taking this medicine
How long you have been taking this medicine
The results of your blood tests
How much your test results change from test to test
If you have just started taking warfarin, you will need blood tests about two times a week. After you have been on warfarin for a while, INRs are not needed as often. Many people on this medicine for a long time only need to get blood tests about once a month. You may need to get INR tests more often if you have changes in your medicines, diet, or health.
If you are told to get a blood test and can’t keep your appointment, call and make a new appointment. If you have changes in bruising, nose bleeding, or gum bleeding, call your health care provider and ask to have your blood checked sooner.
What happens after I get my INR tested? You will get instructions from your health care provider about how much warfarin to take after each INR test. Talk to your provider so you have a plan for getting these instructions after each INR test. They will tell you whether to keep taking the same amount of warfarin or what changes to make.
Your health care provider will ask you about things that can change the INR, such as:
If you have started, stopped, or changed any of your medicines
If you have changed what you eat or drink
If you have had a change in your health
If you have taken your warfarin as directed
If you have missed doses or taken extra doses
What happens if I don’t get my blood tested? Your health care provider decides how much medicine you need to take based on your INR result. Therefore, it is essential that you get your INR checked when scheduled or call immediately if you miss an INR appointment. Changes in your INR can happen quickly if you do not take your dose as directed every day.