Avon Medical Centre - Stratford Doctors

Warfarin Treatment Guidelines

Guidelines for Patients on Warfarin Treatment

The most common reasons that patients may take warfarin are:  blood clots in the legs (DVTs); blood clots in the lungs (pulmonary emboli); abnormal heart beat rhythms (atrial fibrillation) and artificial or damaged heart valves. 

Warfarin is a medicine that is used to prevent blood clots forming.  Patients need regular blood tests to make sure that they are taking the right amount of warfarin. 

Here is how together you and your medical team can help make sure you are taking this life saving medication safely:

  • All patients should have a handbook to record their warfarin blood test results.  This result is called the INR.
  • The INR is a number that shows how easy it is for your blood to clot.  The number should normally be between 2 and 3.  Your doctor will tell you what your “target” INR should be.
  • You should be told how long you should take warfarin.  Many people need lifelong treatment, but some people only need warfarin for 3-6 months.
  • You should expect to have a blood test at least every 4-6 weeks.  When starting warfarin or other medications, patients may need more frequent testing.
  • The practice nurse will phone you after your blood test to tell you what the INR result is, what dose of medication you should be taking and when your next blood test should be. Have your handbook ready so that you can record the result and new warfarin dose.  If you do not hear from the nurse by the end of the next working day please call the surgery.
  • It is extremely important to take the dose you have been advised.  If you forget a dose or take too many tablets please call the surgery and ask to speak to your doctor or the practice nurse.
  • Please make sure that you have the regular blood tests at the time advised by the nurse. Patients who do not have the regular blood tests may be advised that it is safer to stop taking warfarin.
  • Take your warfarin at the same time each day, at around 7pm. This allows your doctor time to phone on the test day and stop the warfarin if your INR is very high. 
  • It is wise for patients taking warfarin to purchase and wear an alert bracelet or pendant.  In an emergency this lets everyone know that you are taking warfarin.
  • Please inform any health care professional looking after you that you are taking warfarin.  Many other medications can dangerously interfere with warfarin.
  • There are some herbal medications that interfere with warfarin.  Please tell your doctor if you are taking or intend to take any herbal medication. 
  • Some illnesses (e.g. diarrhoea, infection or fever) can affect warfarin and your INR. Let your doctor know if you are ill. An earlier blood test may be needed.
  • Before any surgery/dental work tell your surgeon/dentist that you are taking warfarin

Bleeding is the most serious side effect of warfarin.  If anybody who is taking warfarin experiences any of the following symptoms, they must call their doctor immediately: 

  • Red or dark brown urine
  • Red or black stool (bowel motion)
  • Severe headache
  • Unusual weakness
  • Excessive menstrual (period) bleeding
  • Prolonged bleeding from gums or nose
  • Dizziness, trouble breathing or chest pain
  • Unusual pain, swelling or bruising
  • Dark, purplish or mottled fingers or toes
  • Vomiting blood or coughing up blood
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