An INR home testing machine is a small, lightweight instrument that weighs between 5.3 and 28.8 ounces and is used by patients taking warfarin to check their prothrombin time, according to the National Blood Clot Alliance website. The test result is called INR, which stands for international normalized ratio.
Patients taking warfarin regularly monitor their INR and report the results to their doctor, anti-coagulation clinic pharmacist, nurse or independent diagnostic testing facility. The health care professional then instructs the patient on adjusting the warfarin dosage. If the INR is too low, the patient is at risk for blood clotting. If the patient's INR is too high, there is a risk of bleeding, according to National Blood Clot Alliance.