Vitamin K is a fat-soluble vitamin, which means it is absorbed most effectively when ingested with dietary fat. It is best known for its role in helping blood clot properly after an injury. Vitamin K is helpful in this situation because it is responsible for making clotting factors in the liver. Vitamin K also plays an important role in bone health.

Vitamin K comes from the foods that we eat. Plus, bacteria that normally reside in the intestines are able to make vitamin K. Antibiotics may interfere with this normal production. Other circumstances that may lead to vitamin K deficiency include:

• Health problems that can prevent the absorption of vitamin K (such as gallbladder or biliary disease which may alter the absorption of fat), cystic fibrosis, celiac disease, and Crohn's disease
• Ingestion of excessive amounts of mineral oil
• Liver disease
• Use of blood-thinning medications (such as warfarin, see Interactions)
• Ongoing or significant diarrhea (particularly in breast fed infants)
• Long-term use of total parenteral nutrition (TPN; nutrition provided intravenously)
• Continuing hemodialysis
• Serious burns

It is also important to note, that breast fed infants may be at an increased risk for vitamin K deficiency because human milk is not a very good source of this nutrient. Interestingly, though, if a mother eats lots of green vegetables on a daily basis, she can improve the amount of vitamin K in breast milk. In addition, the elderly may also be at an increased risk for vitamin K deficiency they tend take many medications, eat insufficient amounts of vegetables, and may have bacterial overgrowth that impacts vitamin K production in the gut.

Vitamin K deficiency is rare because gut bacteria can produce enough of this vitamin, even if dietary intake is low. Vitamin K deficiency can lead to excessive bleeding (hemorrhage) which may begin as oozing from the gums or nose. Echymoses (bleeding below the skin) and excessive bruising may also be symptoms of vitamin K deficiency.

Vitamin K protects the body against the following:

Excessive Bleeding
Vitamin K is used to reduce the risk of bleeding in liver disease, malabsorption syndromes as described earlier, or in association with long-term use of antibiotics. Vitamin K has been used in the treatment of heavy menstrual bleeding. Use of vitamin K for liver disease, although often attempted, is not generally successful. This is particularly true in the late stages of the disease, because at that point the liver is unable to make the blood clotting factors, no matter how much vitamin K is present.

In the US, Canada, Great Britain, and many other countries, all newborns receive vitamin K injections to prevent the possibility of hemorrhage (particularly in the brain) just after delivery. Newborns are at risk for bleeding in the brain because of the trauma of coming through the birth canal during delivery. Vitamin K is not readily transferred from mother to child during pregnancy. Therefore, even though vitamin K deficiency in the newborn is very rare, it is considered sufficiently dangerous to warrant these measures. Newborns at greatest risk for vitamin K deficiency are those who are born prematurely or whose mother had to take seizure medications during the pregnancy. Mothers on seizure medications are often given oral vitamin K for 2 weeks prior to delivery.

Osteoporosis
Vitamin K is needed for proper use of calcium in bones. Higher vitamin K levels correspond to greater bone density, while low levels of vitamin K have been found in those with osteoporosis. There is increasing evidence that vitamin K supplements improve bone health and reduce risk of bone fractures, particularly in postmenopausal women who are at risk for osteoporosis. In addition, studies of other groups (such as male and female athletes) have also shown bone enhancing benefits from vitamin K supplements.

Snake Bite
Some snake venoms work by destroying vitamin K, and thus the body's ability to clot blood clot. Vitamin K may be injected to stop the bleeding from snakebite.

Cystic Fibrosis
Because of involvement of the pancreas (responsible for making enzymes that help fat absorption) and often the liver with this condition, vitamin K deficiency is common in people with cystic fibrosis. Therefore, supplementation is frequently recommended. Vitamin K deficiency in those with cystic fibrosis is worsened by their recurrent need for antibiotics.

Kidney Stones
Vitamin K may help to prevent the formation of kidney stones. (It is interesting to note that vegetarians, who tend to have a high vitamin K intake, rarely have kidney stones.)

Body Odor
Chlorophyll (a water-soluble source of vitamin K in plant foods) helps control body, fecal, and urinary odor.

Skin Wounds
Water-soluble forms may be used topically to treat skin wounds. This may be due to the antioxidant effect of chlorophyll.

In addition, early test tube studies suggest that vitamin K3 (a synthetic form of vitamin K) may inhibit the growth of certain cancerous bone marrow cells, specifically, chronic myelogenous leukemia (CML) cells. CML is one type of leukemia that is classified as a myeloproliferative disorder. Some researchers are concerned, however, that this form of vitamin K may cause serious anemia in people. More research is needed to assess if this synthetic form of vitamin K is safe and useful for people with CML.

Foods that contain a significant amount of vitamin K include beef liver, green tea, turnip greens, broccoli, kale, spinach, cabbage, asparagus, and dark green lettuce. Chlorophyll, which is water soluble, is the substance in plants that gives them their green color and provides vitamin K.

Freezing foods may destroy vitamin K, but heating does not affect it.

There are three forms of vitamin K:

• Vitamin K1 (phylloquinone, the natural version of K1 and phytonadione, the synthetic type of K1)
• Vitamin K2 (menaquinone)
• Vitamin K3 (menaphthone or menadione)

K1 and K3 are both available as part of multivitamin complexes or alone, in 5 mg tablets. These fat-soluble forms are an excellent source of vitamin K.

Water-soluble chlorophyll is the most common form of vitamin K found over the counter. It is available in tablet, capsule, and liquid forms. Only the topical form is used to treat skin wounds and body odor.

As with all supplements, check with a healthcare provider before taking vitamin K or giving it to a child. In general, people with vitamin K deficiencies related to malabsorption (such as gallbladder or biliary disease, cystic fibrosis, celiac disease, and Crohn's disease) will benefit most from a multivitamin containing vitamin K, rather than an individual vitamin K supplement. In certain circumstances, vitamin K may be administered by injection in to a vein or muscle by a healthcare professional.

Daily intake for dietary vitamin K (according to the U.S. RDA) are listed below:

Pediatric

• Infants birth to 6 months: 2 mcg
• Infants 7 to 12 months: 2.5 mcg
• Children 1 to 3 years: 30 mcg
• Children 4 to 8 years: 55 mcg
• Children 9 to 13 years: 60 mcg
• Adolescents 14 to 18 years: 75 mcg

A single injection of vitamin K is also given at birth.

Adult

• Males 19 years and older: 120 mcg
• Females 19 years and older: 90 mcg
• Pregnant and breastfeeding females 14 to 18 years: 75 mcg
• Pregnant and breastfeeding females 19 years and older: 90 mcg

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable healthcare provider.

Vitamin K crosses the placenta and is also excreted in breast milk. Therefore, pregnant women and women who are breast-feeding should consult a healthcare provider before taking vitamin K supplements.

Those with an unusual metabolic condition called Glucose-6-phosphate dehydrogenase (G6PD) deficiency should avoid vitamin K. Those with G6PD deficiency experience a serious breakdown of red blood cells (called hemolysis) when exposed to certain infections or medications, including vitamin K.

If you are currently being treated with any of the following medications, you should not take vitamin K without first talking to your healthcare provider.

Antibiotics
Antibiotics, particularly a class known as cephalosporins, reduce the absorption of vitamin K. Extended use of antibiotics may result in vitamin K deficiency because these drugs kill not only harmful bacteria, but also beneficial, vitamin K-activating bacteria. This is particularly a problem for people who already have low levels of vitamin K or are at risk for deficiency (such as those who are malnourished, elderly, or taking warfarin).

Doxorubicin
Preliminary evidence suggests that vitamin K3 (a synthetic form of vitamin K) may enhance the chemotherapeutic effects of doxorubicin. However, these results have not yet been demonstrated in people. There is also some concern that vitamin K3 causes severe anemia in people. More research is needed to assess if this synthetic form of vitamin K is safe and useful.

Phenytoin
Phenytoin interferes with the body's ability to use vitamin K. Taking anticonvulsants (such as phenytoin) during pregnancy or while breastfeeding may deplete vitamin K in newborns.

Warfarin
Vitamin K reduces the effects of the blood-thinning medication warfarin, rendering the medication ineffective. Vitamin K should not be taken while taking warfarin, and foods containing high amounts of vitamin K should be avoided.

Weight Loss Products
Orlistat, a medication used for weight loss and olestra, a substance added to certain food products, are both intended to bind to fat and prevent the absorption of fat and the associated calories. Because of their effects on fat, orlistat and olestra may also prevent the absorption of fat-soluble vitamins such as vitamin K. Given this concern and possibility, the Food and Drug Administration (FDA) now requires that vitamin K and other fat soluble vitamins (namely, A, D, and E) be added to food products containing olestra. How well vitamin K from such food products is absorbed and used by the body is not clear. In addition, physicians who prescribe orlistat add a multivitamin with fat soluble vitamins to the regimen.

The possibility of olestra or orlistat interfering with vitamin K absorption is particularly important to know if you already have a vitamin K deficiency (such as with malnourishment or poor fat absorption from cystic fibrosis) or if you have a tendency to bleed (includign if you take the blood thinner warfarin). On the other hand, the fact that vitamin K is now added to olestra-containing food products is also significant if you should not be taking vitamin K (again, for example, if you are on the blood thinner warfarin or you have a G6PD deficiency).

X-rays and Radiation
X-rays and radiation can deplete vitamin K levels and raise vitamin K requirements.

Each of the following may diminish vitamin K absorption and lead to reduced levels in the body:

• Aspirin 
• Cholestyramine, one of a class of medications known as bile acid sequestrants used to lower cholesterol
• Mineral oil laxatives 

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