Hi, The normal range for prothrombin time is 12 - 15 seconds; the range for the INR is 0.8-1.2. Patients who are on oral anticoagulants or blood thinners should have INR between 2.0 and 3.0. While patients who have a risk of clot formation should have INR still higher i.e. 3.5. An INR of 3.9 versus 2.2 means that the blodd has become thinner. A higher INR than the normal range meand that the blood has become thinner.
Hope the information helps.
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