MPA | Pharmacy News

By Carla R. LaMarr, CPhT, LTC project specialist, PharMerica; Reviewed by Amanda Moulton, Pharm.D., pharmacist, PharMerica


INR, which stands for international normalized ratio (INR), is an important lab value to obtain when you are being treated with Coumadin (warfarin), a medication that is known as an anticoagulant.  Various disease states that require anticoagulation therapy include heart attack, blood clots and an irregular heartbeat known as atrial fibrillation. Anticoagulants are essential in the treatment of the previously listed disease states since they will slow blood clotting and prevent the formation of blood clots. INR levels measure the amount of time it will take for your blood to form a clot. The lower the level, the higher the risk for your body to form a blood clot; the higher the value, the longer it will take for your body to form a clot, thus increasing your risk for a bleed.  If INR levels are either too high or too low, a dose adjustment of your medication is necessary.  


A normal INR level is 0.8-1.2 for a healthy individual. When a person is being treated with an anticoagulant such as warfarin, the targeted level should be 2.0-3.0 or 2.5-3.5, depending on diagnosis.  Warfarin is a medication that interacts with certain foods, medications and alcohol due to its mechanism of action.  Due to these interactions, INR levels may potentially be affected.  Please note that certain antibiotics, vitamins, over-the-counter supplements and foods such as green, leafy vegetables may alter the effectiveness of warfarin and in turn INR values. It is also good to remember that if you are taking an anticoagulant and you have an injury that causes bleeding, contact your primary care provider or emergency services immediately as this medication thins the blood and increases the time for bleeding to stop.


Another lab value that may be required for monitoring in addition to INR levels when on warfarin may include a PT (prothromin time), but INR’s are the standard when determining dose adjustments.  It is very important to communicate to your healthcare provider any new medications or vitamins that you take, as well as any dietary changes that occur since all of these could impact your treatment and health.



1.       University of Rochester Medical Center.  Health Encyclopedia. International Normalized Ratio. Accessed April 2017.

2. What is normal INR level. Accessed April 2017.

3.       American Association for Clinical Chemistry. Prothrombin Time and International Normalized Ratio. Accessed April 2017. 

Bookmark and Share  

Search for
Pharmacy News