What foods should you avoid on warfarin?

Foods low in vitamin K (under 10 mcg a serving)

USDA FoodData Central. The Daily Value for vitamin K is 120 mcg. In one study, the INR began to drop at 150 mcg a day of added vitamin K (see the studies below). Cooking shrinks greens, so a cup of cooked greens holds far more leaves than a cup of raw.

• Level E The amount of vitamin K in food may affect therapy with warfarin sodium. Advise patients taking warfarin sodium to eat a normal, balanced diet maintaining a consistent amount of vitamin K. Warfarin sodium, FDA-approved label, drug interactions section, effective 2026-06-25
• Level E People taking warfarin and similar anticoagulants need to maintain a consistent intake of vitamin K from food and supplements because sudden changes in vitamin K intakes can increase or decrease the anticoagulant effect [45]. NIH Office of Dietary Supplements, Vitamin K Fact Sheet for Health Professionals

Text in quotation marks is word for word from the official source. Level E means the position of an expert body or a drug label. How we grade evidence.

Evidence behind the advice

• Level C In people on warfarin, vitamin K began to shift the INR at 150 micrograms a day, and meals of spinach produced only a short-lived response that pointed to poor absorption from the leaf. Blood, 2004
• Level D A case report describes a woman on warfarin whose INR rose to 9 after she stopped eating dill pickles, a vitamin K source. Clin Rheumatol, 2021
• Level B Two weeks of cranberry raised the INR response to a single 25 mg dose of warfarin by 30 percent in 12 healthy men, without changing warfarin blood levels. Br J Pharmacol, 2008
• Level C Among 171 people taking warfarin followed for 16 weeks, those using ginger had about three times the odds of self-reported bleeding. Pharmacotherapy, 2007
• Level D A 71-year-old woman on warfarin was hospitalized with bleeding and an unmeasurable INR after 4 days of goji berry juice, scoring 6 on the Naranjo scale for a probable drug interaction. Pharmacotherapy, 2012

The other side and the limits

• Level B In 30 patients on stable warfarin, 240 mL of cranberry juice daily for 2 weeks left warfarin blood levels unchanged and moved the INR at only one of the measured time points. J Clin Pharmacol, 2009
• Level E The NIH center for complementary health describes the warfarin interaction evidence as conflicting and tells people on warfarin to ask a clinician before using cranberry. NCCIH (NIH), Cranberry: Usefulness and Safety, updated November 2024
• Level B In 12 healthy men given a single 25 mg dose of warfarin after two weeks of garlic, garlic changed neither how the body handled warfarin nor how strongly it thinned the blood, while cranberry in the same trial raised the INR curve by 30%. Br J Pharmacol, 2008
• Level C In volunteers not taking warfarin, untreated natto pushed plasma menaquinone-7 from 1.86 to 14.54 ng/mL five hours after eating, while boiling the same fermented soybeans held the rise to 4.02 ng/mL. J Nutr Sci Vitaminol (Tokyo), 2006

Levels: A is a meta-analysis of trials, B a randomized trial, C an observational study, D lab work or case reports, E an expert position. How we grade evidence.

Steady matters more than low. The FDA label and NIH both ask for a consistent amount of vitamin K, so if you already eat cooked greens most days, the label advice is to keep that steady rather than cut them out. The problem is a sudden change, like starting a daily kale smoothie or dropping salads for two weeks.

The table shows how uneven the foods are. A cup of cooked spinach has about 888 mcg, while a cup of raw spinach has about 121 mcg, because cooking packs more leaves into the cup. Rice, chicken, eggs, bananas and oranges have almost none.

Vitamin K is not the only question. In the studies below, cranberry raised the INR in one small trial (NIH calls the evidence conflicting), ginger use went with more self-reported bleeding, and one woman bled after 4 days of goji berry juice. Ask your pharmacist before adding any of them regularly.

A case report below shows the other direction too: INR rose after a woman stopped eating pickles. If your eating changes for any reason, such as a new diet, illness or travel, tell the clinic that checks your INR.

Evidence behind this note

1. Level E The FDA-approved warfarin label says the amount of vitamin K in food may affect therapy and tells patients taking warfarin to keep the amount of vitamin K in their diet consistent. Warfarin sodium, FDA-approved label, drug interactions section, effective 2026-06-25
2. Level E NIH advises people on warfarin to keep vitamin K intake from foods such as leafy greens consistent, since sudden changes alter the drug's effect. NIH Office of Dietary Supplements, Vitamin K Fact Sheet for Health Professionals
3. Level C In people on warfarin, vitamin K began to shift the INR at 150 micrograms a day, and meals of spinach produced only a short-lived response that pointed to poor absorption from the leaf. Blood, 2004
4. Level D A case report describes a woman on warfarin whose INR rose to 9 after she stopped eating dill pickles, a vitamin K source. Clin Rheumatol, 2021
5. Level B Two weeks of cranberry raised the INR response to a single 25 mg dose of warfarin by 30 percent in 12 healthy men, without changing warfarin blood levels. Br J Pharmacol, 2008
6. Level E The NIH center for complementary health describes the warfarin interaction evidence as conflicting and tells people on warfarin to ask a clinician before using cranberry. NCCIH (NIH), Cranberry: Usefulness and Safety, updated November 2024
7. Level C Among 171 people taking warfarin followed for 16 weeks, those using ginger had about three times the odds of self-reported bleeding. Pharmacotherapy, 2007
8. Level D A 71-year-old woman on warfarin was hospitalized with bleeding and an unmeasurable INR after 4 days of goji berry juice, scoring 6 on the Naranjo scale for a probable drug interaction. Pharmacotherapy, 2012

Written from the positions and data on this page, reviewed by the Bioma editorial system. How we verify.

• Vitamin K: what it does and how much you need
• Kale: what the research says
• Spinach: what the research says
• Collard greens: what the research says
• Broccoli: what the research says
• Brussels sprouts: what the research says
• Cranberry juice: what the research says
• Natto: what the research says