Vitamin K is a vitamin found in leafy green vegetables, broccoli, and Brussels sprouts. The name vitamin K comes from the German word “Koagulationsvitamin.”
Several forms of vitamin K are used around the world as medicine. Vitamin K1 (phytonadione) and vitamin K2 (menaquinone) are available in North America. Vitamin K1 is generally the preferred form of vitamin K because it is less toxic, works faster, is stronger, and works better for certain conditions.
In the body, vitamin K plays a major role in blood clotting. So it is used to reverse the effects of “blood thinning” medications when too much is given; to prevent clotting problems in newborns who don’t have enough vitamin K; and to treat bleeding caused by medications including salicylates, sulfonamides, quinine, quinidine, or antibiotics. Vitamin K is also given to treat and prevent vitamin K deficiency, a condition in which the body doesn’t have enough vitamin K. It is also used to prevent and treat weak bones (osteoporosis) and relieve itching that often accompanies a liver disease called biliary cirrhosis. Vitamin K2 (menaquinone) is taken by mouth to treat osteoporosis and bone loss caused by steroids, as well as to lower total cholesterol in people on dialysis.
People apply vitamin K to the skin to remove spider veins, bruises, scars, stretch marks, and burns. It is also used topically to treat rosacea, a skin condition that causes redness and pimples on the face. After surgery, vitamin K is used to speed up skin healing and reduce bruising and swelling.
Healthcare providers also give vitamin K by injection to treat clotting problems.
An increased understanding of the role of vitamin K in the body beyond blood clotting led some researchers to suggest that the recommended amounts for dietary intake of vitamin K be increased. In 2001, the National Institute of Medicine Food and Nutrition Board increased their recommended amounts of vitamin K slightly, but refused to make larger increases. They explained there wasn’t enough scientific evidence to make larger increases in the recommended amount of vitamin K.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The effectiveness ratings for VITAMIN K are as follows:
More evidence is needed to rate vitamin K for these uses.
The two forms of vitamin K (vitamin K1 and vitamin K2) are LIKELY SAFE for most people when taken by mouth or injected into the vein appropriately. Most people do not experience any side effects when taking in the recommended amount each day.
Pregnancy and breast-feeding: When taken in the recommended amount each day, vitamin K is considered safe for pregnant and breast-feeding women. Don't use higher amounts without the advice of your healthcare professional.
Children: The form of vitamin K known as vitamin K1 is LIKELY SAFE for children when taken by mouth or injected into the body appropriately.
Diabetes: The form of vitamin K known as vitamin K1 might lower blood sugar levels. If you have diabetes and take vitamin K1, monitor your blood sugar levels closely.
Kidney disease: Too much vitamin K can be harmful if you are receiving dialysis treatments due to kidney disease.
Liver disease: Vitamin K is not effective for treating clotting problems caused by severe liver disease. In fact, high doses of vitamin K can make clotting problems worse in these people.
Reduced bile secretion: People with decreased bile secretion who are taking vitamin K might need to take supplemental bile salts along with vitamin K to ensure vitamin K absorption.
Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.
Vitamin K1 might decrease blood sugar. Diabetes medications are also used to lower blood sugar. Taking vitamin K1 along with diabetes medications might cause your blood sugar to go too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.
Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), and others.
Interaction Rating = Major Do not take this combination.
Vitamin K is used by the body to help blood clot. Warfarin (Coumadin) is used to slow blood clotting. By helping the blood clot, vitamin K might decrease the effectiveness of warfarin (Coumadin). Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
Coenzyme Q-10 is chemically similar to vitamin K and, like vitamin K, can promote blood clotting. Using these two products together can promote blood clotting more than using just one. This combination can be a problem for people who are taking warfarin to slow blood clotting. Coenzyme Q-10 plus vitamin K might overwhelm the effects of warfarin and could allow the blood to clot.
Vitamin K1 might lower blood sugar. Using vitamin K1 along with other herbs and supplements that might lower blood sugar might lower blood sugar too much. Herbs that might lower blood sugar include devil's claw, fenugreek, guar gum, Panax ginseng, and Siberian ginseng.
There is a concern that tiratricol might interfere with vitamin K's role in blood clotting.
In animals, high doses of vitamin A interfere with vitamin K's ability to clot blood. But it's not known if this also happens in people.
High doses of vitamin E (e.g. greater than 800 units/day) can make vitamin K less effective in clotting blood. In people who are taking warfarin to keep their blood from clotting, or in people who have low vitamin K intakes, high doses of vitamin E can increase the risk of bleeding.
Eating foods containing butter or other dietary fats in combination with vitamin K-containing foods, such as spinach, seems to increase vitamin K absorption.
The following doses have been studied in scientific research:
There isn't enough scientific information to determine recommended dietary allowances (RDAs) for vitamin K, so daily adequate intake (AI) recommendations have been formed instead: The AIs are: infants 0-6 months, 2 mcg; infants 6-12 months, 2.5 mcg; children 1-3 years, 30 mcg; children 4-8 years, 55 mcg; children 9-13 years, 60 mcg; adolescents 14-18 years (including those who are pregnant or breast-feeding), 75 mcg; men over 19 years, 120 mcg; women over 19 years (including those who are pregnant and breast-feeding), 90 mcg.
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