You may know people who are taking warfarin, but do you know why they take it and what it does for them?

Warfarin is an anticoagulant drug. This means that it increases the time it takes for the blood to clot. If your body makes a clot it can cause serious problems.

Warfarin comes in tablet form and is taken by mouth. It binds with vitamin K found in the blood, reducing the amount of vitamin K available to the liver for use in the body’s clotting cascade. The clotting cascade is the series of processes that occurs within the blood from the time that you (for example) cut yourself to the time that the body has made a clot to stop the bleeding.

Warfarin is used to reduce the likelihood of clots forming and can help stop existing clots from getting larger. It can also be used to treat existing clots, e.g. for someone with deep vein thrombosis or pulmonary embolism. The length of time a person is on warfarin depends on the condition for which it has been prescribed. Everyone who is prescribed the drug should be given a booklet about anticoagulants which contains lots of information on warfarin and advice about food, alcohol and possible interactions with other drugs, as well as a space where they can record their blood results and warfarin doses.

The drug is used to prevent and treat health conditions including:

  • complex congenital heart disease
  • mechanical heart valve replacement
  • atrial fibrillation or atrial flutter
  • heart attack
  • Transient Ischemic Attack (stroke)
  • pulmonary embolism (clot in the lungs)
  • deep vein thrombosis (clot in the veins in the legs)
  • Other surgical procedures (some procedures place a person at a high risk of developing a blood clot)

Whilst on warfarin, the person’s blood will be regularly monitored by blood tests/finger prick tests to measure its INR (International Normalized Ratio). A normal INR result for someone not taking warfarin is 1.0. The higher the reading the more anticoagulated the patient is. The required level of the INR will differ depending on the reason the patient is anticoagulated.

If the INR level goes below the required level, this means that the blood is able to clot more easily and places that patient at higher risk of developing an unwanted clot. Treatment for this is simple: a higher dose of warfarin will be prescribed. If the INR goes above the target range this means the blood will take longer to clot and a lower dose of warfarin will be prescribed.

There are many factors that can affect a persons’s INR result. These include a change in diet, a change in medications, the onset of a new illness, or having to stop taking warfarin because of undergoing a procedure. There are no symptoms of a low INR. However a high INR may result in:

  • bruising more easily
  • bleeding from the nose
  • bleeding from the gums
  • blood in the urine
  • blood in stools
  • unexpected vaginal bleeding/excessively heavy periods

For these reasons it is very important that patients ensure that they get their INR levels checked regularly.

People who take warfarin may need to make minor adjustments to their lifestyle. Ideally, they should not participate in contact sports e.g. rugby or horse riding, due to the increased risk of serious injury and associated bleeding. Alcohol elevates the INR result in everyone, but this effect is greatly increased in those patients taking warfarin. For this reason binge drinking is not advisable – but then, binge drinking is not really advisable for anyone!

Vitamin K is an essential element of the clotting cascade and is found in large quantities in leafy green vegetables, cranberry juice, liver/red meats and soya products to name a few. One of the most important lifestyle adjustments that people with heart conditions can make is to ensure that they have a healthy, balanced diet. Therefore these food groups shouldn’t be totally avoided – just not eaten in excessive amounts. People who take warfarin should be monitored regularly by their healthcare provider, who should ensure that their warfarin dose is suitable, taking their normal diet into account.