Vitamin K
Vitamin K has two forms. The most important form nutritionally (phylloquinone) occurs in plants and is consumed in the diet. The other form (menaquinone) is produced by bacteria in the intestine, but only limited amounts of this form can be absorbed. Vitamin K is necessary for the synthesis of the proteins that help control bleeding (clotting factors) and thus for the normal clotting of blood. It is also needed for healthy bones.
Vitamin K Deficiency
Disorders that interfere with fat absorption can reduce the absorption of vitamin K and cause vitamin K deficiency. Taking large amounts of mineral oil may reduce the absorption of vitamin K. Vitamin K deficiency can develop in people who take certain drugs, including anticoagulants, anticonvulsants, and certain antibiotics.
One form of vitamin K deficiency is hemorrhagic disease of the newborn, characterized by a tendency to bleed. A vitamin K injection is usually given to newborns to protect them from this disease. Breastfed infants who have not received this injection at birth are especially susceptible to vitamin K deficiency.
Symptoms, Diagnosis, and Treatment
The main symptom is bleeding (hemorrhage)--into the skin (causing bruises), from the nose, from a wound, in the stomach (sometimes with vomiting of blood), or in the intestine. Blood may be seen in the urine or stool. In newborns, life-threatening bleeding within or around the brain may occur. Vitamin K deficiency may also weaken bones.
When vitamin K deficiency is suspected, a blood test to measure clotting function is performed. An abnormal test result can also be caused by use of anticoagulants or by liver damage.
Treatment consists of vitamin K injections or adjusting the dose of the anticoagulant. People who have vitamin K deficiency and a severe liver disorder may also need blood transfusions to replenish the clotting factors. The damaged liver may be unable to synthesize prothrombin and other clotting factors even after vitamin K injections.
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