After being diagnosed with a blood clot (thrombosis), many patients are prescribed warfarin for treatment.  Warfarin is a prescription drug that lowers the chance of blood clots developing in the body. This prevents blood clots from forming and causing deep vein thrombosis (DVT), pulmonary embolism (PE), stroke, heart attack, and more. Warfarin works by blocking the formation of vitamin K-dependent clotting factors, substances in the blood that cause clotting.

While warfarin’s ability to stop clotting is a major benefit to blood clot patients, it can also cause problems. If it is too effective at stopping the clotting process, it can lead to uncontrolled bleeding. In order to monitor how effective the warfarin treatment is, doctors test a patient’s “INR” level.

What does INR stand for?

INR stands for International Normalized Ratio.

Doctors measure a patient’s INR level during a PT-INR test. The PT stands for prothrombin time. The test measures how much time it takes for a patient’s blood to clot. This test ensures that patients are receiving the dosage of warfarin that is right for them. If an INR score is too low, a patient can be at risk for a blood clot. However, if the INR is too high, patients could also experience bleeding.

A typical INR score ranges between 2 to 3. The “ideal” INR score can vary from patient to patient.

How often is testing needed?

How often a patient should be tested can vary, depending on how stable their INR is over time. According to the American Heart Association (AHA), patients should be tested at least once a month and, in some cases, as much as twice a week. This testing often involves going to get your blood drawn at a clinic, but can also be done at home in some cases.

Home testing involves patients using an INR monitor and test strips. Patients are taught how to test their own INR level and then report their INR results to their care team, who can then tell patients if they need to adjust their warfarin dosage.

If you are interested in exploring home testing as an option for your care, talk to your doctor about your options.

What can I do to help keep my INR level where it should be?

First, always listen closely to your doctor’s instructions. Patients on warfarin may have their dosages adjusted often, as doctors look to stabilize their INR levels. Always be sure to stay on top of your medication and to take it exactly as your doctor prescribes. For example, if you miss a dose, don’t double up next time you take it. When filling your warfarin prescription, try to fill it at the same pharmacy to ensure the brand of warfarin you’re on stays consistent. It is also key to ensure your doctor knows about all of the other medications you are on, as different medications can interact poorly with warfarin.

When you’re at the doctor’s office, the information they give you can often be overwhelming. Try bringing a notepad and a pen. Write down what your doctor tells you to ensure you aren’t forgetting anything. This is also a great way to remember your questions. If you write them down in your notepad before heading to the doctor’s office, you’re less likely to forget.

A second major thing patients need to watch is their diet. When you are on warfarin, you need to keep track of the foods that may have vitamin K in them. Because warfarin works by blocking vitamin K-dependent clotting factors, increasing your vitamin K intake can make warfarin less effective, lowering your INR level. Foods with high levels of vitamin K include Kale, broccoli, and Brussels sprouts. AHA produced a helpful guide to foods that are high and low in vitamin K, it can be found here.

Your INR level is complex. In addition to vitamin K, any major lifestyle changes can cause your INR level to change. These can range from changing what foods you eat to how much you exercise. Major diet changes, such as starting a new diet or taking new supplements, can cause your INR level to fluctuate. Consulting a doctor is the best way to ensure the lifestyle changes you’re making will positively impact your life.

Looking Forward

Starting a new medication always has its challenges and warfarin is no exception. By knowing your INR level and staying on top of your warfarin dosage, you can help maintain a healthy lifestyle.