INR Blood Test - More Information

This INR test, also known as a PT / PTT / INR test, an INR blood test and INR lab test, measures the PT, PTT and INR blood levels.

The INR test is composed of the PT test and the PTT test. INR stands for international normalized ratio and is a calculated metric used to help manage people on warfarin therapy. Regular INR testing is done to help manage medication doses in patients taking warfarin / Coumadin and may be helpful in people taking vitamin K antagonist medications.

The "INR" in the INR blood test represents the ratio of the prothrombin time measured to the control sample used during testing. Said another way, it is the patient's prothrombin time / normal prothrombin time. The INR test is calculated to create a common numerical system to understand aspects of blood clotting (coagulation) when different types of lab equipment and reagents are used in sample processing. To do so, lab equipment manufacturers utilize something called a International Sensitivity Index (ISI) related to the tissue factors used. The INR lab test is frequently used in helping to track and adjust medication doses of people on warfarin (Coumadin®). As a result, it is sometimes known as a warfarin blood test or a Coumadin® blood test.

Getting an INR test near you at a Quest Diagnostics lab is a fairly standard process. After you place your order online, you get your blood drawn at a local lab and will be notified when your INR lab results are ready. As can be seen on INR sample lab report provided above, your INR level will be reported with some guidelines on target INR ranges based on warfarin use. The PT and PTT results will also be reported for added guidance, and results and any medication adjustments should then be performed with the help of your licensed medical provider.