Dandelion leaves & Warfarin

Publication Date: 
Tue, 11/08/2011
By: Alere Staff

In the springtime, more fresh fruits and vegetables are readily available and often chosen over heavier pastas and carbohydrate comfort foods. During this season, salads become a popular and nutritious choice. They include a variety of leafy greens, which contain moderate to high amounts of vitamin K. In large quantities, this vitamin can reduce the effectiveness of warfarin and lower International Normalized Ratio (INR) test results. To maintain stable INR blood test results, patients are often told to keep their portion sizes consistent and avoid large increases or decreases in leafy greens.1

Not all leafy greens, however, lower INR test results. Dandelion leaves are popular in salads, soups and even wines, and do not lower INR test results. Despite their dark green leaf color, they contain properties that can actually increase INR test results. They contain coumarins, a natural anticoagulant, that can interfere with platelet function.1 Platelets play a key role in normal blood clotting.

Salads should be enjoyed in moderation. As a general rule, the darker the green of some vegetables, the higher the vitamin K content, and the greater the effect on lowering a patient’s INR test results. Patients should remember to track vitamin K intake and keep all scheduled clinic appointments.

Increasing testing frequency is recommended when making any changes to your diet, medication, etc. Studies have shown that increasing testing frequency with weekly testing of INR improves patient safety and helps keep the drug in its therapeutic effective zone.2,3 Weekly testing was shown to be the most effective testing frequency.2 Medicare and many private/commercial insurance reimburse patients for weekly patient self-testing.4 Go to the Getting Started page or call Alere at 1.800.504.4032 for more information about testing your INR at home.

For more information on the vitamin K content in favorite foods, visit our Vitamin K Finder. It is a collection of more than 5,000 choices of foods and beverages that allow warfarin patients to creatively prepare healthy and nutritious meals all year long.

  1. Bristol-Myers Squibb Company. Medication Guide for Coumadin Tablets and Coumadin for Injection [Package Insert]. Princeton, NJ: Bristol-Myers Squibb Company (2009).
  2. Am J Manag Care. 2014;20(3):202-209.
  3. Heneghan C., et al. Self-monitoring of oral anticoagulation: a systematic review and meta-analysis. 2006. Lancet, 367, 404-11.
  4. Center for Medicare and Medicaid Services. Decision Memo for Prothrombin Time (INR) Monitor for Home Anticoagulation Management  (CAG-00087R) [Memorandum]. 2008. Baltimore, MD.