If you are taking warfarin, then INR, testing is a required part of your ongoing therapy. INR stands for “international normalized ratio." It is a standardized reporting system established by the World Health Organization (WHO). It is used as the measure of a patient's level of anticoagulation when being treated with warfarin. INR is monitored to ensure patients taking warfarin are in the therapeutic range.
Your INR results let your doctor know whether you’re taking the right amount of warfarin to keep you in range and on track. Testing is a continual commitment between you and your doctor. However, once you know your options, you’ll see how it can become a simple part of your routine.
1 http://www.stoptheclot.org/learn_more/blood_clot_treatment.htm (accessed January 2018).
2 http://www.ismaap.org/welcome-detail/management-of-longtime-anticoagulation/ (January 2018)
3 Ryan, J. et al. (2008). Journal of Clinical Pharmacy and Therapeutics 33:581-590
4 Fiumara, K. et al. (2009). Circulation 119:e220-e222.
Often called blood thinners, anticoagulants like warfarin (also called Coumadin®) help increase the time it takes for your blood to clot.1 For instance, if you’re taking warfarin and you cut your finger, it may take longer for the bleeding to stop than for somebody who isn’t taking an anticoagulant.
Vitamin K plays a key role in forming clotting factors, which causes the blood to clot. Warfarin blocks the formation of vitamin K-dependent clotting factors, which helps prevent and slow the formation of harmful clots.
If you just found out from your doctor that you need to start taking warfarin, you’re not alone. Every day, millions of people worldwide take anticoagulants.2 They are commonly prescribed for or as a result of:3
• Atrial fibrillation (irregular heartbeat)
• Mechanical heart valves
• Venous thromboembolism
• Thrombophilia (tendency to cause blood clots)
• Heart attack (causing damage to heart muscle)
When you’re prescribed warfarin, regular blood tests are required to ensure your blood isclotting within a target range.1 This is called INR monitoring.
An INR test shows how quickly your blood will clot while you’re on your current dose of warfarin, which helps determine whether your dose needs to be adjusted.
Your individual target range may vary based on disease state and advising doctor’s treatments.
For more information on your range, please contact your doctor.
1 American Heart Association, “A patient’s guide to taking warfarin,” http://www.heart.org/HEARTORG/Conditions/Arrhythmia/PreventionTreatmentofArrhythmia/A-Patients-Guide-to-Taking-Warfarin_UCM_444996_Article.jsp (accessed January 2018).
2 Levi, M. et al. (2009). Seminars in Thrombosis Hemostasis 35:527-542.
All three ways provide accurate results. However, many warfarin patients choose self-testing for the freedom and convenience it offers.
Think about which option works best for you and your lifestyle. All three options provide accurate INR results.
1 The CoaguChek XS system may be used up to a maximum altitude of 14,000 feet.
Like other medications, warfarin can be affected by what you eat and drink. While no foods are off limits, there are three important factors you need to consider.
Produced by your body as part of the clotting process, vitamin K is also found in many green, leafy foods, such as kale, lettuce, spinach and broccoli.
High amounts of vitamin K can reverse warfarin’s blood-thinning effect.1
Does this mean you should cut back on foods high in vitamin K? No, but a consistent diet is important, as your doctor will base your recommended warfarin dose on your regular diet. Consult your doctor with dietary concerns.
Because it immediately decreases your blood’s ability to clot, alcohol should be avoided when taking warfarin. Even if your INR levels remain within the target range, the risk of major bleeding is increased.3 What’s more, after episodes of excessive drinking, clotting can increase, putting you at greater risk of heart attack or stroke.4
Because warfarin can interact with many drugs and supplements,5, 6, 7 tell your healthcare provider about everything you take, including these over-the-counter medications and supplements:
• Acetaminophen (e.g., Tylenol)
• Aspirin, including ointments/creams
• Ibuprofen (e.g., Advil)
• Naproxen (e.g., Aleve)
• Non-steroidal anti-inflammatory drugs (NSAIDs)
• Heartburn or acid reflux medicines (e.g., Nexium, Zantac)
• Cold/allergy medicines
• Herbal supplements (e.g., Ginkgo biloba, ginseng, St. John’s wort)
• Birth control pills
• Vitamin supplements with vitamin K
1 Blood Thinner Pills: Your Guide to Using Them Safely. Agency for Healthcare Research and Quality, Rockville, MD. September 2015. Available at https://www.ahrq.gov/sites/default/files/wysiwyg/patients-consumers/diagnosis-treatment/treatments/btpills/btpills.pdf (Accessed January 2018.)
2 USDA. (Last modified May 2016). USDA National Nutrient Database for Standard Reference, Release 28, Vitamin K Content of Selected Foods (accessed January 2018).
3 American Heart Association. “A patient’s guide to taking warfarin.” http://www.heart.org/HEARTORG/Conditions/Arrhythmia/PreventionTreatmentofArrhythmia/A-Patients-Guide-to-Taking-Warfarin_UCM_444996_Article.jsp (accessed January 2018).
4 Renaud, S.C. and Ruf, J.C..(March 15, 1996). “Effects of alcohol on platelet functions.” Clinica Chimica Acta 246(1-2):77-89. http://www.ncbi.nlm.nih.gov/pubmed/8814972 (accessed January 2018).
5 Coumadin (warfarin sodium) [package insert 293US11PBS01503]. (2011). Princeton, NJ: Bristol-Myers Squibb.
6 Agency for Healthcare Research and Quality, Rockville, MD. (August 2010). “Blood Thinner Pills: Your Guide to Using Them Safely.”, http://www.ahrq.gov/patients-consumers/diagnosis-treatments/btpills/btpills.html# using (accessed January 2018)
7 Mayo Clinic. “Warfarin side effects: Watch for interactions.” http://www.mayoclinic.org/diseases-conditions/deep-vein-thrombosis/in-depth/warfarin-side-effects/art-20047592?pg=2 (accessed January 2018).
1 Coumadin® (warfarin sodium) package insert revised October 2011.
2 American Heart Association. “What is excessive blood clotting (hypercoagulation)?” http://www.heart.org/HEARTORG/Conditions/More/What-Is-Excessive-Blood-Clotting-Hypercoagulation_UCM_448768_Article.jsp (accessed January 2018).
3 Ryan, J. et al. (2008). Journal of Clinical Pharmacy and Therapeutics 33:581-590.
4 American Heart Association. “A patient’s guide to taking warfarin,” http://www.heart.org/HEARTORG/Conditions/Arrhythmia/PreventionTreatmentofArrhythmia/A-Patients-Guide-to-Taking-Warfarin_UCM_444996_Article.jsp (accessed January 2018).
5 Blood Thinner Pills: Your Guide to Using Them Safely. Agency for Healthcare Research and Quality, Rockville, MD. September 2015. Available at https://www.ahrq.gov/sites/default/files/wysiwyg/patients-consumers/diagnosis-treatment/treatments/btpills/btpills.pdf (Accessed January 2018.)
6 Mayo Clinic. “Warfarin diet: What foods should I avoid?” http://www.mayoclinic.com/health/warfarin/AN00455 (accessed January 2018).