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Vitamin K must be present for the proper clotting of the blood. In cases of injury, vitamin K acts as a catalyst, helping to create the clotting factors in blood that prevent hemorrhages. There are a number of chemical forms of vitamin K. Kl occurs in leafy green vegetables, and K2 is formed in the human intestinal tract by bacteria normally present there. Synthetic vitamin K, meniadone, is available only by prescription. Because vitamin K is so readily available no recommended allowance has been set. Nonetheless, certain individuals may need extra vitamin K. Newborn infants may not have the necessary intestinal bacteria that aid in formation of the vitamin. People undergoing long-term treatment with antibiotics that kill intestinal bacteria, or those with liver disease, may develop shortages, resulting in prolonged clotting time or liver damage. Vitamin K deficiencies occur only under severe circumstances and should be treated by a physician. Excessive use of K supplements can be toxic. People with lo~ levels of prothrombin (a blood clotting factor) may be given vitamin K prior to surgery. To protect a newborn infant, the vitamin may be given to the mother prior to delivery and later to the infant. The main source of vitamin K is the bacteria in the intestine. Good food sources include green leafy vegetables such as spinach, kale, and darker lettuce, as well as cauliflower, cabbage, egg yolks, and liver. | 
