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Anticoagulation Clinic

Information for patients taking Warfarin

If you are being referred for the first time you will receive an appointment to be seen in the Anticoagulant Clinic at Bournemouth Hospital where one of the Anticoagulant Practitioners will explain all about Warfarin.

For most subsequent appointments you will be advised when you need a blood test.

This can be at the Pathology Department at Bournemouth or Christchurch Hospital and no appointment is required or the blood specimen can be taken by some GP surgeries but will require an appointment.

It is important that you tell the Anticoagulant Clinic about any medicines that you have started or discontinued.

At the Royal Bournemouth and Christchurch Hospitals NHS Foundation Trust Anticoagulant Service we use an ‘economailer’ which is a letter that you will receive in the post after each blood test telling you how much Warfarin to take and the date for your next blood test.

How do I take my anticoagulant?

Take your anticoagulant once a day, at about the same time, preferably on an empty stomach and washed down with a full glass of water.

If you miss a dose, or take the wrong dose by mistake, make a note in this booklet. Take your normal dose the next day. If the dose you took in error greatly exceeded your normal dose please contact your anticoagulant clinic. You may be given a number of different strength tablets to make up your dose, and it is important that you become familiar with the different strengths and colours that you need to take.

In the UK, the colours of Warfarin tablets are:

  • 0.5mg (500 micrograms) – white
  • 1mg – brown
  • 3mg – blue
  • 5mg – pink

At the Royal Bournemouth and Christchurch Hospitals NHS Foundation Trust Anticoagulant Service 5 mg tablets are not used. You may need a mixture of different coloured tablets to make up your dose. Other anticoagulants may come in different strengths and colours .Do not confuse the dose in mg with the number of tablets that you take.

Monitoring whilst you are taking an anticoagulant

You must have a regular blood test called an International Normalised Ratio test (INR).This is a standard test that measures how long your blood takes to clot. Normally, blood that is not anti-coagulated has an INR of approximately 1.0.

The dose of anticoagulant that you need to take will depend on your INR test result. If your result is out of the range appropriate for your condition, your dose of anticoagulant will be increased or decreased accordingly. The anticoagulant dose required to achieve the target INR varies for each person.

Repeat prescriptions

It is important that checks are performed each time you request and receive a supply of oral anticoagulants.This must include reviewing your blood test results and dose information, and ensuring that it is safe to supply you with more tablets.

When you request a repeat prescription you will be asked to provide information about your INR test results and current dose of oral anticoagulant, which you will have collected and kept in your anticoagulant folder.

Your community pharmacist will also ask to see this information when they dispense your prescription. If you cannot request or collect the prescription yourself, make sure that the person representing you has this information with them. For prescription delivery services, the pharmacist dispensing the prescription should contact you to confirm your INR and current dose. Make sure that you do not run out of tablets and always have at least a week’s supply.

Serious side effects

The most serious side effect of anticoagulants is bleeding. If you experience any of the following, seek medical attention and have an urgent INR test.

  • prolonged nosebleeds (more than 10 minutes)
  • blood in vomit
  • blood in sputum
  • passing blood in your urine or faeces
  • passing black faeces
  • severe or spontaneous bruising
  • unusual headaches

for women, heavy or increased bleeding during your period or any other vaginal bleeding. If you cut yourself, apply firm pressure to the site for at least five minutes using a clean, dry dressing. Seek immediate medical attention if you

  • are involved in major trauma
  • suffer a significant blow to the head
  • are unable to stop bleeding

Going to the dentist

You can still go to your dentist as usual.In the majority of cases your dental treatment can go ahead as normal without your anticoagulant being stopped or the dose being adjusted.However, your dentist will need to see a recent INR test result to ensure that it is safe to provide treatment.

Your dentist will be able to provide you with a leaflet which explains this and give you some additional advice.You should contact your dentist before your appointment in case they need you to have an extra blood test.

Things that can affect the control of anticoagulation

Other medicines

Many medicines can interact with anticoagulants.If, during your course of anticoagulants, you are also starting or stopping another medication, the prescriber may advise that you should have a blood test within five to seven days of starting the new medication. This is to make sure that your INR remains within the desired range. Please contact the anticoagulant clinic for further advice.

If you are planning to buy over-the-counter medicines, including alternative remedies, tell the pharmacist that you are taking an oral anticoagulant and show them your anticoagulant alert card. They can then advise you on medicines that are safe for you to take.

You should not take aspirin unless it has been specifically prescribed by your GP. It is also advisable to avoid other non-steroidal anti-inflammatory drugs like diclofenac or ibuprofen.

Please note that some of these can be bought over the counter in pharmacies with names such as Nurofen®. Paracetamol and codeine-based painkillers are acceptable, although be aware that some paracetamol ‘plus’ products contain aspirin.


It is important to eat a well balanced diet.Consult your doctor or practice nurse if you need to diet to lose weight. Any major changes in your diet may affect how your body responds to your anticoagulant medication.

Foods rich in vitamin K may affect your INR result.Such foods include green leafy vegetables, chick peas, liver, egg yolks, cereals containing wheat bran and oats, mature cheese, blue cheese, avocado and olive oil. These foods are important in your diet but eating them in large amounts may lower your INR result.

Try to take the same amount of these foods on a regular basis.It is the change in the vitamin K intake that affects your INR result. Drinking cranberry juice can also affect your INR and so should be avoided altogether if possible. If your diet changes greatly over a seven-day period, you should have an INR test.


It is recommended that you do not exceed the national guidelines. These are up to three units a day for men, and up to two units a day for women.

One pint of beer is two units; one pub measure of a spirit is one unit; and one pub measure of wine is one unit. It is dangerous to ‘binge drink’ while taking anticoagulants.


Oral anticoagulants can affect the development of a baby in early pregnancy.

Women who are on oral anticoagulants should discuss plans for future pregnancy with their doctor before trying to conceive, wherever possible.

Women who think they have become pregnant while on Warfarin should seek a pregnancy test as soon as possible and, if this is positive, an urgent appointment with a doctor.

You may breast feed while taking anticoagulant medication.


Women may experience heavier periods while they are taking oral anticoagulants and may wish to discuss this with their GP, anticoagulant nurse or pharmacist. Reference – National Patient Safety Agency March 2007 ©

Produced by the British Society for Haematology and the National Patient Safety Agency.

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