Q&A: “My grandma is taking warfarin (blood thinner), do you know what foods she can and can’t eat?”

April 23, 2018

This is a question I was frequently asked as a community dietitian. There is an urban myth that when someone is prescribed warfarin they need to cut out all all green vegetables which is not true.

Warfarin (blood thinner)

For anyone taking warfarin it’s important they continue to enjoy the foods they are used to eating and don’t unnecessarily limit their intake.

Warfarin is a blood thinner which is prescribed as a preventative measure for people who are at risk of having blood clots. These blood clots can cause a stroke or heart attack.

Vitamin K

When people are prescribed warfarin they are advised to take care in eating foods which are rich in vitamin K. Vitamin K acts as a natural blood clotting agent and in large amounts, will react with warfarin to reduce its effectiveness.

Foods rich in vitamin K and regularly consumed in New Zealand include: broccoli, brussel sprouts, cabbage, kale, lettuce, spinach, watercress, beef, liver, soybeans, wheat bran and green tea.


Vitamin K rich foods can be eaten and enjoyed, as long as they are regularly included in meals and consumed in consistent amounts. By consistent amounts, I mean having about the same amount of these vegetables on a regular basis, and not having a large amount one day, followed by none the next few days.

Serving sizes

One to two servings of green vegetable on a daily basis is recommended as part of a balanced diet. A serving is half a cup of cooked green vegetables or a handful of green salad.


If you drink alcohol, try to limit your intake to no more that 2 standard drinks a day, increased alcohol intake will affect blood thinning and may increase bleeding.

Further Info

Keep your doctor informed of any dietary supplements you take and discuss with them vitamin or herbal supplements you are considering taking.

For further information on warfarin access this information sheet on the PHARMAC website.

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