Skip to content
My WebMD Sign In, Sign Up

Coumadin oral

Coumarin Anticoagulants/Vitamin K-Containing Foods

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug, changing your diet or commencing any course of treatment.

Medical warning:

Very important. A change in your diet, medicine, or dosage may be necessary. Promptly consult your doctor or pharmacist.

How the interaction occurs:

When your anticoagulant ("blood-thinner") is taken with foods containing vitamin K, the vitamin K may prevent your anticoagulant from effectively preventing blood clots.

What might happen:

The beneficial effects of your anticoagulant may decrease, which may increase your risk of an unwanted blood clot.

What you should do about this interaction:

Avoid sudden changes in your diet while you are taking this medicine. Foods high in Vitamin K are of the most concern, but the best approach is to try to be consistent in your daily food choices. Do not change the amount of moderate-to-high Vitamin K-containing food in your diet (see the lists below) without first consulting your healthcare professional (e.g., doctor or pharmacist).Also, do not use a strict vegetarian diet (some greens have moderate-to-high Vitamin K content) without first consulting your healthcare professional.Some examples of foods high or moderate in Vitamin K content are listed below: High Level Vitamin K Foods (micrograms per serving listed) include Kale, fresh (547.4 micrograms per 1 cup); Swiss Chard, fresh (298.8 micrograms per 1 cup); Broccoli, frozen, boiled (248.4 micrograms per 1/2 cup); Broccoli, fresh, boiled (210.6 micrograms per 1/2 cup); Spinach, fresh (120 micrograms per 1 cup); Green or Red Leaf Lettuce (117.6 micrograms per 1 cup); Escarole, fresh (115.5 micrograms per 1 cup); Endive, fresh (115.5 micrograms per 1 cup); Cabbage, fresh (101.5 micrograms per 1 cup); Moderate Level Vitamin K Foods (micrograms per serving listed) include Mustard Greens, fresh (95.2 micrograms per 1 cup); Brussels Sprouts, fresh (77.9 micrograms per 1/2 cup); Butterhead Lettuce (67.1 micrograms per 1 cup); Watercress (42.5 micrograms per 1/2 cup); Yellow Snap Beans (41.3 micrograms per 3/4 cup); Kiwi Fruit (38 micrograms per 2 items); Asparagus, fresh (35.7 micrograms per 2/3 cup); Soybeans, dry roasted (31.8 micrograms per 1/2 cup); Split Peas, boiled (27.5 micrograms per 1/2 cup); Green Peas (27.3 micrograms per 1/2 cup); Soybean Oil (26.2 micrograms per 1 tablespoonful); Abalone, Raw (26.1 micrograms per 1/2 cup); Green Beans, cooked (25.8 micrograms per 1/2 cup). Avocados, some varieties of seaweed, and liquid nutritional supplements also contain vitamin K.Contact your doctor or pharmacist for more information. Your healthcare professionals may be aware of this interaction and may be monitoring you for it. Do not start, stop, or change your medicine or diet before checking with them first.

References:

1.BREST AN, BOWER R, HEIDER C. ANTICOAGULANT THERAPY--A CLINICAL DILEMMA. JAMA 1964 Feb 15;187:SUPPL 27-40.
2.Andersen P, Godal HC. Predictable reduction in anticoagulant activity of warfarin by small amounts of vitamin K. Acta Med Scand 1975 Oct; 198(4):269-70.
3.Qureshi GD, Reinders TP, Swint JJ, Slate MB. Acquired warfarin resistance and weight-reducing diet. Arch Intern Med 1981 Mar;141(4):507-9.
4.Kempin SJ. Warfarin resistance caused by broccoli. N Engl J Med 1983 May 19;308(20):1229-30.
5.Karlson B, Leijd B, Hellstrom K. On the influence of vitamin K-rich vegetables and wine on the effectiveness of warfarin treatment. Acta Med Scand 1986;220(4):347-50.
6.Walker FB 4th. Myocardial infarction after diet-induced warfarin resistance. Arch Intern Med 1984 Oct;144(10):2089-90.
7.Martin JE, Lutomski DM. Warfarin resistance and enteral feedings. JPEN J Parenter Enteral Nutr 1989 Mar-Apr;13(2):206-8.
8.Suttie JW. Warfarin and vitamin K. Clin Cardiol 1990 Apr;13(4 Suppl 6):VI16-8.
9.Chow WH, Chow TC, Tse TM, Tai YT, Lee WT. Anticoagulation instability with life-threatening complication after dietary modification. Postgrad Med J 1990 Oct;66(780):855-7.
10.Pedersen FM, Hamberg O, Hess K, Ovesen L. The effect of dietary vitamin K on warfarin-induced anticoagulation. J Intern Med 1991 Jun;229(6):517-20.
11.Dickerson RN, Garmon WM, Kuhl DA, Minard G, Brown RO. Vitamin K-independent warfarin resistance after concurrent administration of warfarin and continuous enteral nutrition. Pharmacotherapy 2008 Mar; 28(3):308-13.
12.Custodio das Dores SM, Booth SL, Martini LA, de Carvalho Gouvea VH, Padovani CR, de Abreu Maffei FH, Campana AO, Rupp de Paiva SA. Relationship between diet and anticoagulant response to warfarin: a factor analysis. Eur J Nutr 2007 Apr;46(3):147-54.
13.Ford SK, Misita CP, Shilliday BB, Malone RM, Moore CG, Moll S. Prospective study of supplemental vitamin K therapy in patients on oral anticoagulants with unstable international normalized ratios. J Thromb Thrombolysis 2007 Aug;24(1):23-7.
14.Kudo T. Warfarin antagonism of natto and increase in serum vitamin K by intake of natto. Artery 1990;17(4):189-201.
15.Sconce E, Avery P, Wynne H, Kamali F. Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin. Blood 2007 Mar 15;109(6):2419-23.
16.Couris R, Tataronis G, McCloskey W, Oertel L, Dallal G, Dwyer J, Blumberg JB. Dietary vitamin K variability affects International Normalized Ratio (INR) coagulation indices. Int J Vitam Nutr Res 2006 Mar;76(2):65-74.
17.Cheng TO. Potential interaction between soy milk and warfarin. Am Fam Physician 2004 Oct 1;70(7):1231.
18.Zandijk E. A patient with lessened sensitivity to acenocoumarol during a period of enteral feeding. Ned Tijdschr Geneeskd 2004 Sep 18; 148(38):1896.
19.van Iersel MD, Blenke AA, Kremer HP, Hekster YA. A patient with lessened sensitivity to acenocoumarol during a period of enteral feeding. Ned Tijdschr Geneeskd 2004 Jun 5;148(23):1155-7.
20.Franco V, Polanczyk CA, Clausell N, Rohde LE. Role of dietary vitamin K intake in chronic oral anticoagulation: prospective evidence from observational and randomized protocols. Am J Med 2004 May 15; 116(10):651-6.
21.Khan T, Wynne H, Wood P, Torrance A, Hankey C, Avery P, Kesteven P, Kamali F. Dietary vitamin K influences intra-individual variability in anticoagulant response to warfarin. Br J Haematol 2004 Feb;124(3):348-54.
22.Cambria-Kiely JA. Effect of soy milk on warfarin efficacy. Ann Pharmacother 2002 Dec;36(12):1893-6.
23.Penrod LE, Allen JB, Cabacungan LR. Warfarin resistance and enteral feedings: 2 case reports and a supporting in vitro study. Arch Phys Med Rehabil 2001 Sep;82(9):1270-3.
24.Petretich DA. Reversal of osmolite-warfarin interaction by changing warfarin administration time. Clin Pharm 1990 Feb;9(2):93.
25.Homma K, Wakana N, Suzuki Y, Nukui M, Daimatsu T, Tanaka E, Tanaka K, Koga Y, Nakajima Y, Nakazawa H. Treatment of natto, a fermented soybean preparation, to prevent excessive plasma vitamin K concentrations in patients taking warfarin. J Nutr Sci Vitaminol (Tokyo) 2006 Oct; 52(5):297-301.
26.Oren B, Shvartzman P. Unsuspected source of vitamin K in patients treated with anticoagulants: a case report. Fam Pract 1989 Jun;6(2):151-2.
27.Ovesen L, Lyduch S, Idorn ML. The effect of a diet rich in brussels sprouts on warfarin pharmacokinetics. Eur J Clin Pharmacol 1988; 34(5):521-3.
28.Akrabawi SS. Warfarin and enteral nutrition products. J Am Diet Assoc 1986 Aug;86(8):1096.
29.Howard PA, Hannaman KN. Warfarin resistance linked to enteral nutrition products. J Am Diet Assoc 1985 Jun;85(6):713-5.
30.Zallman JA, Lee DP, Jeffrey PL. Liquid nutrition as a cause of warfarin resistance. Am J Hosp Pharm 1981 Aug;38(8):1174.
31.Lader E, Yang L, Clarke A. Warfarin dosage and vitamin K in Osmolite. Ann Intern Med 1980 Aug;93(2):373-4.
32.O'Reilly RA, Rytand DA. "Resistance" to warfarin due to unrecognized vitamin K supplementation. N Engl J Med 1980 Jul 17;303(3):160-1.
33.Michaelson R, Kempin SJ, Navia B, Gold JW. Inhibition of the hypoprothrombinemic effect of warfarin (Coumadin) by Ensure Plus, a dietary supplement. Clin Bull 1980;10(4):171-2.

See 602 Reviews for this Drug. - OR -

Review this Treatment

Find a Drug:

by name or medical condition or shape/color (Pill Identifier)

(for example: aspirin)

(for example: diabetes)

Report Problems to the Food and Drug Administration
 
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Health Solutions From Our Sponsors

Ask the pharmacist

Questions about medications? Get expert answers by video or live chat about allergies, pregnancy, sleep, and more.
See the Ask the Pharmacist event schedule.

Ask a Question

Popular Slideshows & Tools on WebMD

tea
What you should eat.
Woman sitting in front of UV lights
Is yours working?
woman using breath spray
What's causing yours?
colon xray
Get the facts.
MS Overview
Recognizing symptoms.
bowl of yogurt with heart shape
Eat for a healthy heart.
woman doing pushups
To help you get fit.
Colored x-ray of tooth decay
Know what to look for.
Woman sitting with child
Do you know the symptoms?
fruit drinks
Foods that can help you focus.
Sad dog and guacamole
Don't feed this to your dog.
Thyroid exam
See how much you know.

Women's Health Newsletter

Find out what women really need.

WebMD the app

Get trusted health information. Whenever. Wherever... with your iPhone, iPad or Android.

Find Out More

IMPORTANT: About This Section and Other User-Generated Content on WebMD

The opinions expressed in WebMD User-generated content areas like communities, reviews, ratings, or blogs are solely those of the User, who may or may not have medical or scientific training. These opinions do not represent the opinions of WebMD. User-generated content areas are not reviewed by a WebMD physician or any member of the WebMD editorial staff for accuracy, balance, objectivity, or any other reason except for compliance with our Terms and Conditions. Some of these opinions may contain information about treatment or uses of drug products that have not been approved by the U.S. Food and Drug Administration. WebMD does not endorse any specific product, service, or treatment.

Do not consider WebMD User-generated content as medical advice. Never delay or disregard seeking professional medical advice from your doctor or other qualified healthcare provider because of something you have read on WebMD. You should always speak with your doctor before you start, stop, or change any prescribed part of your care plan or treatment. WebMD understands that reading individual, real-life experiences can be a helpful resource but it is never a substitute for professional medical advice, diagnosis, or treatment from a qualified health care provider. If you think you may have a medical emergency, call your doctor or dial 911 immediately.