Why do I need anticoagulant treatment?
There are many reasons why you may have been prescribed anticoagulant medication. The most common are:
Deep vein thrombosis
This occurs when a blood clot forms in one of the large veins in your leg or arm.
This is a blood clot that forms in, or travels to, your lungs.
This term refers to an irregular heart rhythm. This occurs when the atria (small pumping chambers of the heart) do not contract simultaneously. This means that blood does not flow through them as rapidly as it should and makes the blood more likely to clot. If a clot becomes dislodged it can travel to the brain and result in a stroke. It may also travel to other parts of the body. The likelihood of stroke in patients with atrial fibrillation is approximately five times higher than that of the general population. Warfarin can reduce the risk of stroke by 60 to 70 per cent.
Mechanical heart valves
If you have been fitted with a mechanical heart valve you will need long-term anticoagulation treatment to prevent blood clots forming on the valve. If blood clots were to form on a mechanical valve it would stop working properly.
Please ask your nurse if you would like more information about why you have been prescribed anticoagulant therapy.
For how long will I need to take warfarin?
You may need to take warfarin for a relatively short period of time (e.g. three to six months) if you have had a clot in your leg, for example. You are likely to be on warfarin for the rest of your life if you have a mechanical heart valve.
The appropriate length of treatment will be written in your yellow anticoagulant booklet and will be discussed with you.
Warfarin comes in four different strengths, these are:
0.5mg white tablets
1mg brown tablets
3mg blue tablets
5mg pink tablets
Please keep a supply of all four strengths as the dosage of warfarin you need will depend on the results of regular blood tests and may change from time to time.
Why do I need regular blood tests?
You will need to have regular blood tests to ensure that the blood clotting is kept at a safe and effective level. The blood test you will have is called an INR (International Normalised Ratio).
If you are not taking warfarin your normal INR will be about 0.9 to 1.2. When you are prescribed warfarin your INR will be kept within a range of either 2.0 to 3.0, 2.5 to 3.5, or 3.0 to 4.0 depending on your reason for anticoagulation.
Our aim is to monitor your INR and to advise you of the correct amount of warfarin to take. This will keep your INR within the desired range.
How much warfarin will I need to take?
The required daily dose of warfarin is different for each patient. Your dose of warfarin will depend on the result of your blood test.
When you first start taking warfarin your INR will be checked every few days and the dose of warfarin will be prescribed according to the results. The aim is to find the dose of warfarin that you can take regularly to keep your INR within the desired range.
As your INR and dose stabilises you will need blood tests less frequently. However, your INR can vary from time to time, therefore you will need to attend the anticoagulant clinic at regular intervals so that your blood can be monitored and your dose adjusted to keep it within the desired range.
When should I take warfarin?
Warfarin should be taken at the same time everyday, preferably in the evening between 6 pm and 8 pm.
If you forget to take your dose at the usual time, please take it as soon as you remember, provided that you remember on the same evening. Please do not take the missed dose the next morning or double your dose the next day.
If you do not remember the missed dose until the next day then you should simply continue with your usual dose in the evening. Taking too much warfarin can cause bleeding and can be dangerous.
Does warfarin have any side effects?
Side effects from warfarin treatment are rare but some patients may experience nausea, diarrhoea, a rash or hair loss. If they do occur, please report them to the anticoagulant clinic.
Are there any risks associated with taking warfarin?
The main risk of taking warfarin is from bleeding. Bleeding may be a sign that your INR is too high. You should contact the anticoagulant clinic or your GP if you experience any unexpected bleeding.
Signs of bleeding include:
- Unexplained severe bruising
- Prolonged bleeding from small cuts
- Nose bleeds
- Bleeding gums
- Blood in urine
- Red or black stools
- Unusually heavy periods or bleeding between periods
Will other medication I take affect warfarin?
Some medication may increase or decrease the effect of warfarin, including some antibiotics and some medication prescribed for heart disease. You should tell the anticoagulant clinic if you have been prescribed new medication or if you have stopped taking any medication.
It is important to inform the clinic at the time these changes occur. Please do not wait until your next regular appointment if this is more than one week away.You may need to have your INR checked soon after starting or stopping your medication.
The staff nurse will advise you if an earlier blood test is required. Please check with your pharmacist when you buy over-thecounter medication as some of these may interact with warfarin. You should especially avoid those which contain aspirin.
Non-steroidal anti-inflammatory medication (e.g. ibuprofen/Nurofen) can also interact with warfarin. The occasional use of paracetamol is not a problem but if you need to take this regularly (for more than two days) it may interact with warfarin.
Some vitamin tablets and herbal remedies have also been shown to affect warfarin. Please always check with your pharmacist and the nurse specialist anticoagulation.
What should I do if I am unwell?
Prolonged bouts of nausea, vomiting and diarrhoea should be reported to the anticoagulant clinic or GP; such episodes may affect your ability to absorb warfarin, and your dose of warfarin may need to be changed. If you are ill with a fever (e.g. influenza or a chest infection) you should also inform your GP as this can also affect warfarin.
If you are admitted to hospital please check with a member of the medical staff when your next appointment for the anticoagulant clinic is, before you go home. You will probably need an appointment a few days after you are discharged. If an appointment has not been arranged for you please contact the anticoagulant clinic when you arrive home.
Female patients of childbearing age will need to take precautions to avoid pregnancy while they are taking warfarin. Warfarin may harm an unborn child during the early weeks of pregnancy.
If you are planning to become pregnant it is important that you discuss this with your doctor so that special arrangements can be made to ensure safe anticoagulation treatment throughout your pregnancy.
Can I drink alcohol?
Too much alcohol or changes in alcohol consumption can increase the effect of warfarin. It is safe to drink alcohol in moderate amounts (e.g. one to two units daily).
Do I need to alter my diet?
You should try to eat a well-balanced diet. Dramatic changes in diet can upset warfarin control.
You should not go on crash diets or eat foods that contain vitamin K in excess (such as spinach, asparagus, broccoli, brussel sprouts, lettuce, avocado, liver, eggs or oats). You do not need to cut them out completely, but you should eat them in moderation.
Who should I tell that I am taking warfarin?
Please tell your dentist before any appointment as there may be a risk of bleeding during some dental procedures.
Please tell any doctor who treats you. If you have to undergo a surgical procedure there may be a risk of bleeding and your warfarin treatment may need to be stopped.
Will I be able to participate in sports?
Moderate exercise (e.g. walking, jogging, or swimming) is fine. However, you should avoid contact sports and those activities in which physical injury is likely to occur. Injury will increase the risk of bruising and bleeding while taking warfarin.
The clinic is managed by a staff nurse in the outpatient department under the supervision of the consultant haematologist.
When you attend, a blood sample will be taken for the INR. This is sent to the laboratory to be analysed.
Appointments between 8:30 am and 9:30 am in phlebotomy. Results from the Monday clinic will be ready on Monday afternoon. These results will be sent to you by a letter (first class post) unless there is a need to change your warfarin dose. If this is the case we will telephone you with the dose change and also send you a letter.
Appointments between 1 pm and 4 pm in phlebotomy. Results from the Wednesday clinic will be ready on Thursday morning between 11 am and 12.30 pm.
These results will be sent to you by letter (first class post) unless there is a need to change your warfarin dose. If this is the case we will telephone you with the dose change and also send you a letter.
Appointments between 8 am and 9 am in phlebotomy. Results from the Thursday clinic will be ready on Thursday afternoon between 2 pm and 4.30 pm. These results will be sent to you by letter (first class post) unless there is a need to change your warfarin dose.
If this is the case we will telephone you with the dose change and also send you a letter. If there have been any changes in circumstances since your last appointment (e.g. change of address or GP) please see the receptionist in the outpatient department and please make sure you tell the staff nurse or phlebotomist who will record the changes.
It is essential to advise the staff nurse of any change in medication.
Please ask the receptionist at the outpatient department to inform the staff nurse if you would like to see the doctor. The doctor is only available on Monday from 9.30 am to 12 noon and on Thursday between 9.30 am and 12 noon.
We advise you to see the doctor if you are, or have been:
- Recently discharged from hospital
- Aware of recent changes in your medication/condition or treatment
- Suffering from episodes of bleeding (e.g. nose bleeds)
- Suffering from excessive bruising
Warfarin dose queries
If you have any queries about your warfarin dose please contact the pathology department via the hospital switchboard on 01895 823 737.
Urgent or emergency situations
If you need to speak to someone urgently and you are unable to reach a member of the anticoagulation team, please contact your GP (general practitioner). If it is an emergency situation (such as if you are bleeding) you may want to consider visiting your local accident and emergency (A&E) department. Please note that Harefield Hospital does not have an A&E department.