Which laboratory value must be monitored with the use of warfarin?

Monitoring the International Normalized Ratio (INR) is essential for patients on warfarin because it directly assesses the blood's coagulation status. Warfarin is an anticoagulant that works by inhibiting vitamin K epoxide reductase, which is vital for the synthesis of clotting factors II, VII, IX, and X. The INR is used to determine how effectively warfarin is working to thin the blood and prevent clots while avoiding excessive bleeding.

The target INR typically depends on the condition being treated but generally falls between 2.0 and 3.0 for most indications. Regular monitoring ensures that the levels remain within this therapeutic range, allowing healthcare providers to adjust the dosage of warfarin as needed to minimize the risk of complications associated with both under-anticoagulation (which can lead to thrombosis) and over-anticoagulation (which can lead to hemorrhage).

While other laboratory values, such as creatinine, hematocrit, and potassium, are important for assessing a patient's overall health and potential side effects of various treatments, they do not provide the specific information necessary to manage warfarin therapy effectively. Hence, the INR is the critical laboratory value to monitor when a patient is on war