Warfarin and diet

What you eat and drink can affect warfarin. The most important thing is to keep your diet stable. If you make any changes to your regular diet, tell your doctor, nurse or pharmacist.

Foods and juices

Warfarin interferes with how your liver uses vitamin K taken from your diet. Some foods are rich in vitamin K and these can affect how warfarin works. As part of a healthy balanced diet, you can continue to eat foods that contain vitamin K in moderate amounts. You don’t need to change your regular eating habits. There is no “correct” amount of vitamin K that you should eat. But, it is important to avoid large changes in the amount of food you eat containing vitamin K.

It is also important to consider the amount of vitamin K you are eating in situations when your diet may change, such as during illness, travel, fad diets, hospitalisation and after surgery. Before making any changes to your diet talk to your health professional.

Foods that are rich in vitamin K 
Vegetables
  • Asparagus
  • Broccoli
  • Brussel sprouts
  • Leafy greens such as cabbage, kale, lettuce, spinach, watercress, silverbeet
  • Mung beans, green beans, peas, sugar snap peas
  • Soybeans
  • Chickpeas
Other
  • Liver
  • Egg yolks
  • Mature cheese and blue cheese


Fruit
  • Avocados
  • Kiwi fruit
  • Blackberries
  • Blueberries
  • Raisins
Drinks (known to affect warfarin)
  • Green tea
  • Cranberry juice 
  • Chamomile tea
  • Grapefruit juice
  • Pomegranate juice

Alcohol

Alcohol affects your liver. If you are taking warfarin, it is fine to drink small amounts of alcohol. Generally, 1 to 2 standard drinks per day are considered a safe limit. Having more than this can increase your risk of bleeding. Avoid drinking large amounts of alcohol over a short time. Read more about what is a standard drink.

Herbal or 'natural' products

Some herbal or 'natural' products are known to have an effect on warfarin.
Always check with your doctor or pharmacist before taking herbal preparations or dietary supplements. Let them know if you are already taking supplements when warfarin is prescribed for you.

Examples of herbal or 'natural' products known to have an effect on warfarin
  • cannabis
  • Chinese wolfberry
  • chamomile tea
  • chitosan
  • co-enzyme Q10
  • cranberry
  • dong quai
  • echinacea
  • fenugreek
  • fish oils (e.g. cod liver oil)
  • ginkgo biloba
  • garlic
  • ginger
  • ginseng
  • glucosamine,
  • green tea
  • kava kava
  • liquorice
  • St John’s Wort

Multivitamins

These are fine to take, but check the label and choose a brand without vitamin K.

References

  1. Tan C, Lee S. Warfarin and food, herbal or dietary supplement interactions. Br J Clin Pharmacol 2020;87(2):352-374.
  2. Campbell P, Gallus A. Managing warfarin therapy in the community. Aust Prescr. 2001;24:86-9
  3. Interactions with warfarin BPAC, NZ, 2007
Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, Pharmacist, Auckland Last reviewed: 10 Oct 2021