Warfarin Management

What is Warfarin?

Warfarin is a prescription medication that is used to prevent harmful blood clots from forming or growing larger. Not all blood clots are harmful, some are even beneficial. However, certain medical conditions may cause harmful blood clots to form in areas of the body that they should not, such as the heart, brain and lungs. It is important to know why you need to take warfarin. If you are not sure why you need this medication, ask your doctor.

How Does Warfarin Work?

Clot formation in the body is a complex process that involves many substances called clotting factors. Warfarin blocks the type of clotting factor that requires Vitamin K to work properly. Although Warfarin is often called a “blood thinner,” it doesn’t actually thin the blood. It prevents the Vitamin K dependent clotting factors from working properly. As a result, the blood does not clot as rapidly, and this in turn prevents harmful blood clots from forming.

How Does My Diet Affect my Warfarin Level In My Body?

Warfarin blocks the Vitamin K dependent clotting factor, and much of the Vitamin K in our body comes from the food that we eat. Therefore, it is important to eat a consistent amount of foods that contain Vitamin K. The highest amount of Vitamin K is found in green and leafy vegetables. It is for this reason that patients who take Warfarin should be aware of the Vitamin K level in the foods that they eat, and to avoid sudden changes in diet. You do not need to avoid foods that contain Vitamin K, you just need to make sure that your daily level of Vitamin K is consistent. If your diet changes suddenly for any reason, such as illness or to lose weight, this may affect the level of vitamin K in your blood. A sudden increase or decrease of Vitamin K in your diet can decrease or increase the effect of Warfarin.

What Else Can Affect the Warfarin level in My Body?

Besides green, leafy vegetables, other foods may interfere with the effectiveness of Warfarin, such as:

  • Canola oil
  • Soybean oil
  • Mayonnaise
  • Green Tea
  • Blueberries/blueberry products
  • Cranberry juice/cranberry products
  • Alcoholic beverages

The most important thing to remember is to eat what you normally eat and do not make any sudden changes in your diet without notifying our Warfarin Department.

Why Does My Blood Have to Be Monitored?

The purpose of Warfarin therapy is to decrease the clotting tendency of the blood, but not to prevent it from clotting completely. As we have established, many factors can increase or decrease the effectiveness of Warfarin. It is for these reasons that it is important to monitor the effect of Warfarin closely with blood testing.

The blood test used to measure the time it takes for blood to clot is referred to as a prothrombin time test, or protime (PT). The PT is reported as the International Normalized ratio (INR), which is a more standard way to express the PT value among different labs. The target range for your INR depends on your medical condition, or the reason for taking the Warfarin. It is important for you to know your target range and to also know your most recent INR result.

Below target, your blood is “thick” and places you at an increased risk of clot formation. The lower the number the greater the risk. Above target your blood is “thin” and places you at an increased risk of bleeding. The higher the number the greater the risk.

Where Can I Go To Get My INR Checked?

At Hamilton Cardiology Associates, we have a dedicated staff in our Warfarin Department who follow a specific dosing and monitoring protocol. Our staff is available to answer your questions and concerns and can be reached at 609-581-5704 Monday through Friday 8am- 4:30pm. We offer convenient options for INR monitoring.

We can give you a prescription to go to your local lab (Labcorp, Quest, or a hospital lab). Mobile lab phlebotomy services may be available for homebound patients. We will receive the result and discuss recommendations with you over the phone. For patients who are receiving long-term warfarin therapy, we may be able to request a home machine for you to test the INR yourself, if so desired. With all these options, the staff at Hamilton Cardiology is available to monitor your INR and manage your warfarin dosing.

How Often Do I Need to Check My INR?

Once the INR is consistently maintained in the target range, INR testing should be performed at least once a month. However, if the INR is out of range, it should be performed more frequently. At Hamilton Cardiology Associates, we have dedicated staff in our Warfarin Department who follow a specific dosing and monitoring protocol. New changes in diet, new medication changes, stress and illness may all affect the INR level, and may require changes in your Warfarin dosing, even if your INR level was in the target range when last checked. If you experience any of these changes, it is important to notify the Warfarin Department. They will check your INR more frequently and may possibly adjust the Warfarin dose to ensure that your INR remains in the target range.

When should I take my Warfarin?

Warfarin should be taken as prescribed in the evening. The dose of warfarin may vary from day to day, or may be changed, based on the INR level. It is very important that you take the medication as prescribed, in the evening. If you miss a dose, do not try to “catch up”. Instead, call the warfarin department and they will provide you with dosing instructions. Many of our patients use a “pill box” to ensure they take their Warfarin as instructed and to avoid missing a dose(s).

What Are The Complications of Warfarin?

Frequent INR monitoring is often required to ensure that the INR level remains in the target range. This is the best way to minimize the chance of complications from having an INR level too high (chance of bleeding increased) or too low (chance of clotting increased). These are the two most serious complications of Warfarin therapy. Signs of unusual bleeding include and should be reported immediately to the Warfarin department (After hours please call the service at 609-584-1212):

  • Bleeding from the gums
  • Blood in the urine
  • Bloody or dark stool
  • Nosebleeds
  • Vomiting and/or coughing up small amounts of blood

In addition to these signs, additional symptoms that should be reported immediately to the Warfarin Department include:

  • Severe headache, confusion, weakness or numbness
  • Headache that is severe or unusual
  • Bleeding from minor injury that will not stop
  • Fall or injury to the head


How Can I Prevent Complications of Warfarin Therapy?

The most important thing you can do to prevent complications from Warfarin therapy is to be an active participant in your care or in the care of your loved one. Compliance with the recommended medication dosing and INR

testing schedule is crucial for success, as well as an open communication with our Warfarin Department. It is very important to report new medication changes (including antibiotics, herbal medicines, and over the counter medications), changes in weight or diet, sudden illness, or any other changes in your lifestyle. If you accidently miss a dose, do not double the dose to “catch up”. Instead, call our Warfarin Department.

Other simple changes to decrease the risk of bleeding while taking Warfarin include the following:

  • Use a soft-bristle toothbrush
  • Floss with waxed floss rather than unwaxed floss
  • Shave with an electric razor rather than a blade
  • Take care when using sharp objects, such as knives and scissors
  • Avoid activities that have a risk of falling or injury (e.g. contact sports)
  • Wear medical identification: medical alert bracelet, necklace, or similar alert tag at all times
  • Always carry a list of your current medications on your person, including your current dose of Warfarin

What Other Resources Are Available for Me?

There are a number of resources available on the internet, but it can be difficult to know which ones are reputable. Some recommended sites include:

The National Institutes of Health

Dr Gourmet

The North American Thrombosis Forum

American Heart Association