About Anticoagulant Medication and INR

What is “blood thinner” and why do I have to take it?

“Blood thinner” is a commonly used and misleading name substituted for “anticoagulant medication”. This medication interrupts the blood clotting mechanism and is required when the possibility of blood clot formation exists-it does not “thin” the blood. Blood clots can be stationary (thrombosis) or they can travel in the bloodstream (embolism) and lodge in a vital organ or artery and block blood flow. The most common reasons for using anticoagulants are 1) arrythmias (irregular heartbeats) and 2) an artificial substance is introduced into the blood stream such as an artificial heart valve, dialysis graft, left heart assist device, etc.15 International Normalized Ratio (INR) is a measurement of the level of anticoagulant medication activity in the blood. An INR of 1.0 (one) is normal for people not taking anticoagulant medication. For patients with mechanical heart valves, an INR of 2-3.5 is recommended.15 The generic name for this medicine is warfarin sodium and the most common brand name is Coumadin®.16 Warfarin sodium has been used for more than forty years and is safe and effective when taken as directed.

What is a platelet inhibitor?

The most commonly used platelet inhibitor is aspirin, but there are several others. These drugs decrease the ability of platelets to initiate the clotting sequence.

Can I test my blood at home for “blood thinner” effectiveness?

If you are prescribed anticoagulant medication, home monitoring of INR level has been shown to reduce postoperative complications by as much a 50%.17 Your insurance coverage may pay for lease of the monitor and the test cartridges. Medicare coverage is available three months after surgery. You can purchase these materials with a prescription if your insurance does not pay for them. A good web site to check out these devices/tests is www.hometestmed.com for Quality Assured Services (QAS), the leading supplier of home testing devices and monitoring. On-X Life Technologies Inc. and QAS have formed an alliance called On-X Valve INR Care to help patients receive training and supplies needed for home monitoring of INR level.


For further information about On-X Valve INR Care, please call (800) 504-3916 or (888) 339-8000.