Advice and Information

Further information to help you understand about your medication, and some advice on managing your diet and lifestyle can be obtained from the information below.

• Warfarin

• Warfarin and Other Medication

• Warfarin and Diet

• Atrial Fibrillation and Heart Failure

• Warfarin Coluor Chart

You may also wish to visit the following website, which you may find useful.

For any other questions, in relation to your Anticoagulation or any other medication query, you may also speak to your pharmacy clinician, or you use the contact us page to send us your query.


About Warfarin

Warfarin belongs to the group of medicines known as anticoagulants. It is used to prevent and treat the formation of harmful blood clots within the body by reducing the effects of vitamin K, which is a vitamin present in the body, essential in the process of blood-clotting. Warfarin is available in tablet form and is sometimes known as: Marevan. You may notice the use of either of these names on the packaging of your medicine.


Before taking Warfarin

Before taking warfarin make sure your doctor or pharmacist knows:

• if you are pregnant, trying for a baby or breast-feeding

• if you suffer from liver or kidney problems

• if you have recently had surgery of any kind or recently had a baby

• if you have a stomach ulcer or have ever had a stomach ulcer

• if you suffer from any unusual bruising or bleeding

• if you suffer from uncontrolled hypertension (high blood pressure)

• if you suffer from an infection of the tissues surrounding the heart called bacterial endocarditis

• if you have ever had an allergic reaction to this or any other medicine

• if you are taking any other medicines, including those available to buy without a prescription, herbal and complementary medicines


How to take Warfarin

• Always read the manufacturer's information leaflet, if possible, before beginning treatment.

• Take warfarin exactly as directed by your doctor or anticoagulant clinic.

• Do not stop taking warfarin without speaking to your doctor first.

• You should have been given a treatment booklet with your tablets. Read and follow the instructions carefully before beginning treatment.

• Warfarin is for you. Never give it to others, even if their condition appears to be the same as yours.

• Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of Warfarin contact your doctor or go to the accident and emergency department of your local hospital at once. Always take the container with you, if possible, even if it is empty.


Getting the most from your treatment

• Before taking any 'over-the-counter' medicines, always check with your pharmacist which medicines are safe for you to take alongside warfarin.

• Do not take medicines containing aspirin unless prescribed by your doctor.

• Always attend your regular appointments with the doctor or anticoagulant clinic. You will need to have regular blood tests, especially during the first few weeks of treatment, to ensure that the dose of warfarin you are taking is correct for you.

• You should carry your treatment booklet with you at all times, ideally in your wallet or purse.

• Before having any kind of surgery, including dental or emergency treatment, tell the doctor, dentist or surgeon you are taking warfarin and show the person carrying out the tests or treatment, your warfarin treatment booklet.

• Warfarin is used to prevent blood clots forming and therefore thins the blood, it is important that you take care not to knock, cut or bruise yourself while you are taking warfarin. Inform your doctor if you suffer any falls, blows or injuries. You should also take special care when brushing your teeth or shaving. Use a soft toothbrush, be gentle when using dental floss and if possible use an electric razor.

• Changing your diet suddenly can affect your warfarin levels, especially if you begin to eat more vegetables and salad or if you change the amount of fatty foods you have been eating. You should not begin a weight reducing diet without discussing it with your doctor first.

• Avoid drinking cranberry juice while you are taking this medicine as it may affect the levels of warfarin in your body.

• Alcohol should only be drunk in moderation. Alcohol can also affect the levels of warfarin in your body.


Can Warfarin cause problems?

As well as their useful effects all medicines can cause unwanted side effects. Speak to your doctor or pharmacist if any of the following side effects continue or become troublesome.

Skin rashes, thinning of the hair, diarrhoea, purple toes, feeling or being sick.

Important: If you notice any unusual bruising, bleeding, blood in the urine, blackened stools or jaundice (yellowing of the skin and whites of the eyes) contact your doctor or anticoagulant clinic immediately.

If you experience any other worrying or troublesome side effects, which you think may be due to this medicine, discuss them with your pharmacist.


How to Store Warfarin

• Keep all medicines out of the reach of children.

• Store in a cool, dry place away from direct heat and light.

• Never keep out of date or unwanted medicines. Either discard them safely out of the reach of children or take them to your local pharmacist who will dispose of them for you.

Warfarin and Other Medication
This fact sheet is intended to help those affected by atrial fibrillation (AF) understand warfarin and the effects other medications may have on the effectiveness of this therapy.

Warfarin is a medication which inhibits the clotting process, thereby reducing the risk of AF- related stroke.

People on warfarin are required to have regular blood tests to check for INR (international normalised ration), a measure of the blood’s clotting capability. Warfarin works by interfering with how the liver uses the Vitamin K taken in our diet. Many other medications are also broken down by the liver and they may affect how effectively warfarin thins the blood.

Medications can increase the effect of warfarin and thus a lower dose may need to be taken, or they may decrease the effect of warfarin so a higher dose may need to be taken.

People taking warfarin together with long-term medications do not need to worry, but when some medications are started, or doses are adjusted, increased monitoring of the INR is required so that the right dose of warfarin is given and the blood remains within INR range.

Medications that increase the effects of warfarin include:

Amiodarone heart rhythm medication
• Aspirin pain killer
• Allopurinol used in gout
• Ampicillin antibiotic
• Atorvastatin cholesterol medication
• Celecoxib anti-inflammatory pain killer
• Cefalexin antibiotic
• Cefradine antibiotic
• Cimetidine indigestion and stomach ulcer healing medication
• Citalopram antidepressant
• Ciprofloxacin antibiotic
• Clarithromycin antibiotic
• Clopidogrel antiplatelet medication
• Cranberry juice drink
• Dexamethadone oral steroid medication (at high dose only)
• Diclofenac anti-inflammatory pain killer
• Dipyridamole antiplatelet medication
• Disulfiram used in alcohol misuse therapy
• Entacapone used in Parkinson’s disease
• Erythromycin antibiotic
• Esomeprazole indigestion and stomach ulcer healing medication
• Etodolac anti-inflammatory pain killer
• Ezetimibe cholesterol medication
• Fluconazole as oral antifungalnmedication
• Flutamide used in prostate cancer
• Fluoxetine antidepressant
• Glucosamine health supplement for joint pain
• Ibuprofen anti-inflammatory pain killer
• Itraconazole as oral antifungal medication
• Ketoconazole as oral antifungal medication
• Levothyroxine thyroid replacement hormone
• Mefenamic acid anti-inflammatory pain killer and used for period pain
• Meloxicam anti-inflammatory pain killer
• Metronidazole antibiotic
• Miconazoleas oral or topical anti-fungal medication
• Mirtazepine antidepressant
• Neomycin antibiotic
• Norfloxacin antibiotic
• Omeprazole indigestion and stomach ulcer healing medication
• Orlistat anti-obesity medication
• Oxytetracycline antibiotic
• Piroxicam anti-inflammatory pain killer
• Pantoprazole indigestion and stomach ulcer healing medication
• Paroxetine antidepressant
• Prednisolone oral steroid medication (at high dose only)
• Proguanil malaria treatment and prophylaxis
• Rosuvastatin chlolesterol medication
• Sertraline antidepressant
• Sibutramine anti-obesity medication
• Simvastatin cholesterol medication
• Sixaxentan used to treat hypertension
• Sodium valporate anti-epileptic medication
• Sulfinpyrazone gout medication
• Tamoxifen used in breast cancer
• Tetracycline antibiotic
• Testosterone male hormone supplement
• Tramadol pain killer
• Trimethoprim antibiotic
• Venlafaxine antidepressant


Medications that decrease the effect of warfarin include:

• Barbiturates sedative medication
• Bosentan used to treat hypertension
• Carbamazepine anti-epileptic medication
• Griseofulvin as an oral antifungal medication
• Phenytoin anti-epileptic medication
• Primidone anti-epileptic medication
• Rifampicin antibiotic
• St John’s Wort antidepressant (use with warfarin is not recommended)
• Sucralfate indigestion and stomach ulcer healing medication
• Vitamin K vitamin supplement


If you are on warfarin and you are concerned about interactions with other drugs you are taking, or you are considering taking drugs, cold and ’flu medications or herbal remedies, you should seek advice from a GP, an anticoagulation clinic, a pharmacist or a qualified healthcare professional.

Warfarin and Diet
This factsheet is intended to help those affected by atrial fibrillation understand more about the interaction between warfarin and certain types of food, to help patients maintain a stable INR level.

Many people with atrial fibrillation may and that warfarin therapy is recommended to thin the blood and reduce their risk of stroke.
Warfarin is a very effective medication. However, it does require regular monitoring to assess how thin it makes the blood. It works by interfering with how the liver uses the vitamin K taken in our diet.

Warfarin’s effectiveness is thus affected by the amount of vitamin K in the diet. If the diet is reasonably consistent, then the amount of vitamin K in your diet will be matched by the warfarin dose.

If your diet contains foods rich in vitamin K, there is no need to change your diet or restrict these foods from normal levels of consumption.

If you wish to make a more sustained change to your diet, such as eating green leafy vegetables due to their rich calcium content, you should discuss this with your anti-coagulation clinic or your doctor, as they may wish to monitor your blood a little more frequently to ensure the warfarin continues to work effectively.

If you change your diet to contain foods that are richer in vitamin K then you will and you require more warfarin. If the diet changes to contain more foods that are low in vitamin K then your warfarin dose may need to be reduced.

A simple rule is that leafy green vegetables tend to be rich in vitamin K and root vegetables, fruits and cereals tend to be low in vitamin K.
It is always best to discuss your dietary needs with a qualified nutritionist or medical professional.
Cranberries can affect warfarin in several different ways, and not just due to the vitamin K content.

If you are going to start consuming cranberries or cranberry juice on a regular basis you should let your warfarin clinic know because your warfarin dose may need adjusting. In some instances cranberry juice has been reported to increase your chance of bleeding. Whilst taking Warfarin you are advised to avoid cranberry juice.


Foods rich in vitamin K include:

• Asparagus
• Green beans
• Blackberries
• Blueberries
• Broccoli
• Brussels sprouts
• Cabbage
• Chicory
• Collard greens
• Kale
• Kiwi fruit
• Lettuce
• Mungo beans
• Mustard greens
• Peas
• Pine nuts
• Raisins
• Sugar snap peas
• Soybeans
• Spinach
• Swiss chard
• Watercress

Foods low in vitamin K include:

• All cereals (including flour etc)
• Apples
• Bananas
• Beef
• Cherries
• Chicken
• Fish
• Lamb
• Lemons
• Melons
• Oranges
• Peaches
• Pork
• Shellfish
• Strawberries
• Tofu

Within our normal diet other factors that can interact with warfarin include:
Alcohol: This affects the way that the body, particularly the liver, functions. Taken in a sensible manner and in moderation it is not totally contraindicated. However, periods of marked excess must be avoided.

Natural health food products: These are popular additions to the diet and may potentially affect warfarin therapy, or they may interact with the natural clotting of the blood. The following is not an extensive list. However, any addition of this kind of product to the diet should be discussed with your doctor or anticoagulation clinic:

• American ginseng
• Asian ginseng
• Chinese angelica
• Chinese ginseng
• Chinese wolfberry
• Chondroitin plus glucosamine
• Coenzyme 010
• Devil’s claw
• Dong quai
• Essence of tortoise shell
• Feverfew
• Fenugreek together with boldo
• Fish oil supplements that contain eicosapentaenoic acid(EPA) and docosahexaenoic acid (DHA)
• Ginkgo biloba
• Ginseng
• Green tea
• Horse chestnut
• Japanese ginseng
• Korean ginseng
• Lycium barbarum
• Methyl salicylate (used on the skin)
• Papaya extract
• St. John’s Wort
• Vitamin A
• Vitamin K
• Wintergreen (used on the skin)

Although these lists look restrictive and extensive, the key is to eat a sensible diet. Take the
warfarin at approximately the same time each day. If you wish to make major changes to your diet or start taking a ‘health supplement’, discuss this with your doctor or the clinic which monitors your warfarin therapy. In general they will not restrict your choices but may wish to increase the level of monitoring for a period as you make changes. Once your blood levels are seen to be stable again, then you will return to your normal monitoring intervals.

If you become ill it is important to remember that this may affect your INR level, and it would be advisable for you to have more frequent blood tests to be certain that your INR level is stable.

These lists are not intended to be comprehensive, but as a guide to patients, carers and healthcare professionals

Atrial Fibrillation and Heart Failure
This factsheet is intended to help patients and carers affected by heart failure understand the condition, its relationship with AF, and the treatment options available

Atrial fibrillation (AF) is a common disorder, in which the upper chambers of the heart, the atria, become affected by disorganised and chaotic electrical impulses, making them ‘wobble’ or fibrillate somewhat, rather than squeezing normally with co-ordination and effciency.

The condition is more prevalent in older people.

The atria are a bit like the fuel injectors in a car; you don’t need them, but the main engine runs a lot more effciently when you have them!

The heart can lose up to 20% of its overall output in AF compared to when it is in normal rhythm, which is why some people can feel tired or more short of breath when in AF.

Heart failure (HF) is a rather scary and dramatic term that simply means the heart is not pumping strongly enough to meet normal demands. It can be caused by a range of illnesses and conditions. The symptoms can range from almost none, to leg swelling, severe breathlessness, which can restrict a patient from simply moving from a bed to a chair, or from getting dressed easily.

Heart failure is also known as congestive heart failure (CHF) or congestive cardiac failure (CCF). It may be confused with heart attack.

Causes of HF may include heart attack (myocardial infarction) and other conditions such as high blood pressure, valvular heart disease, cardiomyopathy and AF-related rapid heartbeat.

Thanks to modern day treatments, many patients with HF will feel pretty normal performing everyday activities, but upon exertion, tiredness can come on much sooner than usual.

For a variety of reasons, occurrence of AF becomes much more likely in someone who has HF.

The combination of AF and heart failure exacerbates the heart’s ability to pump effciently further, and this may make the sufferer feel even worse.

The presence of AF increases the risk of someone suffering a stroke. When AF and heart failure are seen in the same person, this risk becomes much higher. If you are known to have AF together with heart failure, you and your clinician should discuss anticoagulation (sometimes known as blood thinning) to reduce the stroke risk.

AF in otherwise normal hearts can be diffcult to treat because it is very patient-specific, but there are several medication and/or procedural options which are available to treat this condition.

With heart failure, AF becomes more diffcult and risky to treat, and some of these drugs and procedures may even cause deterioration.

Thus, AF in association with heart failure causes real problems by

• increasing symptoms

• increasing risk of strokes

• being more diffcult to treat, with lower success rates and higher risks associated with treatments.

In the UK, cardiologists recognise AF and HF as a new ‘epidemic’ following an increase in
diagnoses, and with cases set to rise in the future.

Whilst the combination of having AF and HF is a challenge, it is not all doom and gloom.
Certainly, when AF first strikes a heart failure patient, the sudden change in heart rate and effciency can make the patient feel terrible and may even provoke a stay in hospital.
However, once balanced out, the outlook can be significantly better.

There are many specialist treatments that might be ordered, but because these depend on
specific and complex details, and every patient is different, patients should not feel disappointed if they do not qualify for some of these strategies.

Lifestyle changes such as stopping smoking, light exercise and dietary adjustments can alleviate HF.

Some treatments are still regarded as experimental at the time of writing. The following may be considered appropriate:

• cardioversion, usually in combination with powerful medication

• insertion of a pacemaker or ventricular assist devices

• pacemaker combined with ablation of the AV node (“ablate and pace”)

• Ablation, to address the AF.

The important point is that if a patient with HF develops AF, they should be assessed reasonably rapidly, even if they feel relatively well, as changes in treatment will almost certainly be necessary.

Further information can be found in AF Association information resources:

• Pacemaker and AV Node Ablation for AF patient information fact sheet

• Ablation for atrial fibrillation patient information booklet

• Cardioversion of atrial fibrillation patient information booklet

Warfarin Colour Chart