Atrial Fibrillation and Heart Failure - 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 affective 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 affectiveness 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 affectively.

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
• 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