https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/SR25/nutrlist/sr25w430.pdf and http://www.nal.usda.gov/fnic/foodcomp/Data/HG72/hg72_2002.pdf
Assessment and Plan: Vitamin K
- Vitamin K is best known for its role in assisting blood to clot, or coagulate. Vitamin K is a fat-soluble vitamin found in a number of foods, including leafy green vegetables. Vitamin K deficiency is rare.
- In patients, taking warfarin, it is important to consume consistent amounts of vitamin K in the diet in order for the PTINR to attain and remain within stable range. Vitamin K supplements, or foods containing high amounts of vitamin K, should not be consumed with warfarin. Instead, a diet while on warfarin can include low to moderate amounts of vitamin K containing food sources as long as the same type and amount is consumed every day so that vitamin K intake remains consistently the same.
- Vitamin K levels may be reduced by the use of antibiotics, especially concerning for patient taking warfarin which may result in significant elevation of the PTINR and should be monitored by daily PTINR levels (1).
- High dose of vitamin E reduced body stores of vitamin K (2).
- For patients taking warfarin, brewed black tea or green tea in consistent small amounts (up to 2 cups per day) will not affect PTINR. However, it may be an overlooked source of vitamin K (3,4,5). If the whole ground leaves are used, vitamin K is present in much higher amounts
- The research the vitamin K content in foods, please see: Nutritive Value of Foods, United States Department of Agriculture, Agricultural Research Service, Home and Garden Bulletin Number 72. May be accessed at: https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/SR25/nutrlist/sr25w430.pdf
