In patients taking warfarin, which laboratory value is typically monitored on a monthly basis?

In patients taking warfarin, which laboratory value is typically monitored on a monthly basis?

• A. Platelet count
• B. INR
• C. Hematocrit
• D. Blood glucose

Answer: (B)

Warfarin reduces vitamin K–dependent clotting factors, so the key to safe and effective therapy is tracking how long the blood takes to clot in a standardized way. The INR provides a consistent measure of anticoagulation across different labs and is what clinicians use to adjust warfarin dosing. Keeping the INR within the therapeutic range minimizes the risk of stroke from clotting and the risk of serious bleeding. Once a stable range is reached, monthly checks are common to ensure it stays within target. Platelet count isn’t a direct indicator of warfarin effect, since warfarin doesn’t primarily affect platelets. Hematocrit reflects red cell concentration and can indicate bleeding or anemia but doesn’t measure anticoagulation status. Blood glucose is unrelated to warfarin’s anticoagulant effect.

Warfarin reduces vitamin K–dependent clotting factors, so the key to safe and effective therapy is tracking how long the blood takes to clot in a standardized way. The INR provides a consistent measure of anticoagulation across different labs and is what clinicians use to adjust warfarin dosing. Keeping the INR within the therapeutic range minimizes the risk of stroke from clotting and the risk of serious bleeding. Once a stable range is reached, monthly checks are common to ensure it stays within target.

Platelet count isn’t a direct indicator of warfarin effect, since warfarin doesn’t primarily affect platelets. Hematocrit reflects red cell concentration and can indicate bleeding or anemia but doesn’t measure anticoagulation status. Blood glucose is unrelated to warfarin’s anticoagulant effect.