The prothrombin time (PT) – along with its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) – are assays evaluating the extrinsic pathway and common pathway of coagulation. 1) APTA Acute Care section, Lab values interpretation resources, Update 2013. 2) Takahashi J et al, Usefulness of White Blood Cell Differential for Early Diagnosis of Surgical Wound Infection Following Spinal Instrumentation Surgery, SPINE Volume 31, Number 9, pp 1020–1025. INR Nursing Considerations, Normal Range, Nursing Care, Lab Values Nursing NRSNG. Loading. Unsubscribe from NRSNG? Cancel Unsubscribe. Working. Subscribe Subscribed Unsubscribe 82K. Loading. Normal INR Levels. The normal range for a healthy person not using warfarin is 0.8–1.2. However, this is a dangerously low INR for a person using Warfarin. A prothrombin time test tells you how long it takes your blood to clot. Learn what it looks for, when you might need one, and what the results mean. Learn what it looks for, when you might need. Prothrombin time (PT) is a blood test that measures the time it takes for the liquid portion (plasma) of your blood to clot. A related blood test is partial thromboplastin time (PTT). Common causes of a prolonged PT include vitamin K deficiency, hormone drugs including hormone replacements and oral contraceptives, disseminated intravascular coagulation (a serious clotting problem that requires immediate intervention), liver disease, and the use of the anticoagulant drug warfarin. Additionally, the PT result can be altered by a diet high in vitamin K, liver, green tea, dark. PT INR normal values are important figures that help doctors determine the ability of a person’s blood to clot. The standard values of PT INR may vary from lab to lab, and so it is very important to have the PT INR results interpreted by qualified physician. A prothrombin time (PT) is a test used to help detect and diagnose a bleeding disorder or excessive clotting disorder; the international normalized ratio (INR) is calculated from a PT result and is used to monitor how well the blood-thinning medication (anticoagulant) warfarin (Coumadin®) is working to prevent blood clots.