Prothrombin Time (PT) and International Normalized Ratio (INR) are important blood tests used to assess the clotting function of the blood, which helps doctors evaluate the risk of bleeding or excessive clotting. PT measures the time it takes for blood to clot by assessing the function of various clotting factors, mainly those produced by the liver, including factors I, II, V, VII, and X. The test is commonly used to monitor patients who are taking anticoagulant medications like warfarin, as these drugs work by interfering with the clotting process. PT is usually measured in seconds, with normal values ranging between 11 and 13.5 seconds, although these values may vary slightly depending on the laboratory or testing equipment used. The INR is a calculated value derived from the PT test and is used to standardize results across different laboratories and testing methods, ensuring consistent and accurate interpretation of the results. The INR is especially helpful for patients on blood thinners, as it provides a universal scale to monitor the effectiveness of the medication. The normal INR range for individuals not on anticoagulants is typically between 0.8 and 1.2. However, for patients on blood thinners, the target INR range may vary, often between 2.0 and 3.0, depending on the condition being treated, such as atrial fibrillation or deep vein thrombosis (DVT). An elevated PT/INR can indicate a prolonged clotting time, which may result from liver disease, a vitamin K deficiency, or the use of anticoagulant therapy. A low PT/INR may suggest a risk of excessive clotting, which can lead to conditions such as stroke or heart attack. These tests, when interpreted in conjunction with clinical symptoms and medical history, help healthcare providers adjust medications and make informed decisions about a patient s ’ treatment and care.