Warfarin and dietary advice

Dietary Advice for Patients taking Warfarin

A well balanced diet is important to health. A balanced diet means eating a variety of healthy foods including pulses, grains, fruits and vegetables.

When taking warfarin you should avoid sudden or drastic changes to your diet as this can lead to changes in your INR (blood test). If you are planning to make changes to your diet you should discuss them with the person monitoring your INR, as the dose you take may need to be changed.

It is important to eat regular meals and to avoid binging or starving.


Aim to reduce high fat content foods containing saturated fats and cholesterol. Saturated fats are found in animal products such as red meats, in dairy products such as butter, cream and cheese and in some plant oils. Cholesterol is found mainly in animal and dairy products.

Changing suddenly to a low fat diet will affect your INR result and again will need to be discussed with the person monitoring your INR.

Herbal Remedies

Some herbal remedies have properties that can either increase or decrease the action of oral anticoagulation and should be avoided e.g. St John’s Wort, Danshen, Ginkgo biloba to name but a few.

It is always best to discuss this with the person monitoring your blood tests before considering herbal remedies.

Cranberry Juice & Cranberry Tablets

There have been some reports that large quantities of cranberry juice and cranberry tablets will raise the INR. One or two small glasses per day are probably all right. Again the message is consistency. Do not change the amount that you would usually drink or suddenly start to drink it.


Alcohol can significantly raise the INR result. It is usually safe to drink 1 or 2 units on a regular basis, if it is consistent. It is important not to binge drink. This will put you at serious risk of haemorrhage. A unit is equivalent to half a pint of beer, a glass of wine (125ml) or a pub measure of spirit.

Dietary Supplements

Many dietary supplements contain Vitamin K. If these were required it would be better if they were taken following medical advice. Other vitamins such as vitamin E can affect your INR result. Calcium supplements taken 2 or 3 times a day can reduce the absorption of oral anticoagulation. Fish oils such as Cod liver oil and omega 3 can have an effect on the INR.

It is important that the person monitoring your INR is aware if you start or stop taking dietary supplements.

Vitamin K

Vitamin K plays an important role in the blood clotting process. It is needed for them to be effective by a number of the clotting factors. Most oral anticoagulants work by preventing vitamin K from acting on these clotting factors, slowing the clotting process down. It is important to eat regularly without making big changes to your diet so that the vitamin K made by the body is kept at a constant level.

Vitamin K is also present in some of the foods that we eat. It is mainly found in dark green leafy vegetables. Eating too much can reduce or reverse the action of oral anticoagulants. It is important to include these foods in your diet but to maintain a consistent amount of foods containing vitamin K so that fluctuations in the INR do not occur.

It is recommended that you eat five servings of fruit and vegetables per day, but no more than three servings of dark green vegetables per week. Do not eat these dark green vegetables all on the same day but spread them evenly through the week. These vegetables include broccoli, cabbage, Brussel sprouts, spring greens and spinach greens and spinach.

Foods containing high amounts of Vitamin K

Portion size guide

  • Pork or beef liver (4oz or 100g)
  • Avocado (½ medium sized)
  • Asparagus (10 spears)
  • Broccoli (6-7 small/medium florets)
  • Brussels sprouts (12 sprouts)
  • Cabbage (4 heaped dessert spoons)
  • Watercress (¼ bunch)
  • Kale (3 heaped dessert spoons)
  • Spinach (3 rounded dessert spoon