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Registered Nurse (RN)
Lab Values
INR Lab Value

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INR Lab Value

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INR Lab Value

Because of the variability in reagents used to calculate the prothrombin time (PT) between laboratories, the INR or PT ratio was developed to create an international standard. It is the ratio between the patient’s PT to a control PT.
0.8-1.2 Normal Range
.(8) Ball - (1) Wand . (2) Tutu Normal Range

INR or PT Ratio is a normalized value ratio that standardizes the measurement among labs for PT. The normal range for INR or PT ratio is between 0.8-1.2, but check your lab's range as it can differ slightly. Remember that because it is a ratio you want the value to be close to 1.


Patients on warfarin (Coumadin) are monitored via their INR, which should be 2.0 to 3.0 (higher than the normal range). Important to note, a patient’s ideal INR must be individualized for
each patient according to indication for anticoagulation. For many patient’s, that means an INR between 2 and 3. For others, the range may be as high as 2.5-3.5.

(2) Tutu - (3) Tree

Patients on warfarin (Coumadin) should have values between 2 to 3. Patients with mechanical heart valves may require a higher INR. Of note, patients with early valve designs (such as ball and cage) require an INR of 3.5.


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