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\nVitamin K is a nutrient that the body needs to stay healthy. It\u2019s important for blood clotting and healthy bones and also has other functions in the body. If you are taking a blood thinner such as warfarin (Coumadin), it's very important to get about the same amount of vitamin K each day.
\nThe amount of vitamin K you need depends on your age and sex. Average daily recommended amounts are listed below in micrograms (mcg).
\nLife Stage | \nRecommended Amount | \n
---|---|
Birth to 6 months | \n2.0 mcg | \n
7\u201312 months | \n2.5 mcg | \n
1\u20133 years | \n30 mcg | \n
4\u20138 years | \n55 mcg | \n
9\u201313 years | \n60 mcg | \n
14\u201318 years | \n75 mcg | \n
Adult men 19 years and older | \n120 mcg | \n
Adult women 19 years and older | \n90 mcg | \n
Pregnant or breastfeeding teens | \n75 mcg | \n
Pregnant or breastfeeding women | \n90 mcg | \n
Vitamin K is found naturally in many foods. You can get recommended amounts of vitamin K by eating a variety of foods, including the following:
\nYou can find links to more food sources of vitamin K in the last section of this fact sheet, Where can I find out more about Vitamin K?
\nVitamin K is found in multivitamin/mineral supplements. Vitamin K is also available in supplements of vitamin K alone or of vitamin K with a few other nutrients such as calcium, magnesium, and/or vitamin D. Common forms of vitamin K in dietary supplements are phylloquinone and phytonadione (also called vitamin K1), menaquinone-4, and menaquinone-7 (also called vitamin K2).
\nVitamin K deficiency is very rare. Most people in the United States get enough vitamin K from the foods they eat. Also, bacteria in the colon make some vitamin K that the body can absorb. However, certain groups of people may have trouble getting enough vitamin K:
\nSevere vitamin K deficiency can cause bruising and bleeding problems because the blood will take longer to clot. Vitamin K deficiency might reduce bone strength and increase the risk of getting osteoporosis because the body needs vitamin K for healthy bones.
\nScientists are studying vitamin K to understand how it affects our health. Here are some examples of what this research has shown.
\nVitamin K is important for healthy bones. Some research shows that people who eat more vitamin K-rich foods have stronger bones and are less likely to break a hip than those who eat less of these foods. A few studies have found that taking vitamin K supplements improves bone strength and lessens the chances of breaking a bone, but other studies have not. More research is needed to better understand if vitamin K supplements can help improve bone health and reduce osteoporosis risk.
\nScientists are studying whether low blood levels of vitamin K increase the risk of coronary heart disease, perhaps by making blood vessels that feed the heart stiffer and narrower. More research is needed to understand whether vitamin K supplements might help prevent heart disease.
\nVitamin K has not been shown to cause any harm. However, it can interact with some medications, particularly warfarin (Coumadin); see the information below.
\nYes, some medications may interact with vitamin K. Here are a few examples:
\nVitamin K can have a serious interaction with the blood thinner warfarin (Coumadin). If you take warfarin, make sure that the amount of vitamin K you consume from food and supplements is about the same every day. A sudden change in the amount of vitamin K you get can cause dangerous bleeding (if you consume less) or blood clots (if you consume more).
\nAntibiotics can destroy the good bacteria in your gut. Some of these bacteria make vitamin K. Using antibiotics for more than a few weeks may reduce the amount of vitamin K made in your gut and, therefore, the amount available for your body to use.
\nSome people take bile acid sequestrants (such as cholestyramine [Questran] and colestipol [Colestid]) to lower blood cholesterol levels. These medications can reduce the amount of vitamin K your body absorbs, especially if you take them for many years.
\nOrlistat (Alli and Xenical) is a weight-loss drug. It reduces the amount of fat your body absorbs and can decrease the absorption of vitamin K.
\nTell your doctor, pharmacist, and other health care providers about any dietary supplements and prescription or over-the-counter medicines you take. They can tell you if the dietary supplements might interact with your medicines or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients such as vitamin K.
\nPeople should get most of their nutrients from food and beverages, according to the federal government\u2019s Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber, and other components that benefit health. In some cases, fortified foods and dietary supplements are useful when it is not possible to meet needs for one or more nutrients (for example, during specific life stages such as pregnancy). For more information about building a healthy dietary pattern, see the Dietary Guidelines for Americans and the U.S. Department of Agriculture\u2019s (USDA's) MyPlate.
\nThis fact sheet by the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your health care providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.
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