Reasons, Preparation & Procedure For Conducting a INR Blood Test

Submitted on March 27, 2012

INR blood testing or the International Normalized Ratio is a test that is done in combination with other tests known as the PT or Prothrombin Time and PTT or Partial Thromboplastin Time. The primary reason for performing these tests is to find out the ability of blood to be able to clot. The results derived from conducting a PT test differs in their values because of the tissues that are added to the blood sample as the manufacturers of these tissues are different. Blood tests INR helps in resolving this problem by giving a uniform and standardized result even if the test is carried out at a different location. Each of the manufacturers gives an ISI value to the tissue factor that enables them to compare to a sample that is internationally standardized.


The blood INR test may be ordered to be done by your doctor on a regular basis if you are on medication for anti coagulants. This is in order to check if the person is responding to treatment and also to identify if there are any signs that show a person is suffering from excessive bleeding. These can include bleeding from the nose, heavy bleeding during menstrual cycles, bleeding gums, bleeding after an injury and so on. This test is especially important before a surgery to find out the extent to which blood clots.


You may have to abstain from food for a couple of hours before the test and especially not eat beef, pork, broccoli, green tea, chick peas, turnip greens and soybean as they will not give you the accurate result. Also, if you are taking any medications especially antibiotics it might affect the result of the test and thus, your doctor may advise you not to take them on the day of the test. Make sure that you tell your doctor about all such medications that you are taking.


Blood is taken from the vein through a syringe and collected in a test tube that contains liquid citrate and further testing is carried out from there on. The result is determined in terms of numbers and a high INR level of 5 indicates that the person is most likely to start bleeding while on the other hand, a low level of INR that is about 0.5 means that the person is at a high risk of getting a clot