Vitamin K is essential in the production of prothrombin, a substance necessary for the clotting of blood. It is also instrumental in bone formation and repair. In addition, Vitamin K helps convert glucose into glycogen as a molecule in the liver. Vitamin K deficiency may result in abnormal bleeding.
Interestingly, while Vitamin K is found in some foods, the majority is synthesized by the normal flora, or "friendly bacteria", in our intestines. As a result, primary Vitamin K deficiency is uncommon in healthy adults. Some individuals who receive an extended course of antibiotic therapy may require Vitamin K supplementation because the antibiotics reduce the number of bacteria in the intestine. People with some form of liver disease also have a higher risk of Vitamin K deficiency. Certain drugs, such as, anticonvulsants, aspirin, and very large doses of Vitamin A or E may be at an increased risk for Vitamin K-related hemorrhagic disease.
Signs of Vitamin K deficiency can include easy bruising, nosebleeds, or blood in the urine or stool. Oozing of blood from puncture sites or incisions may occur after minor injury.
When taken in large doses during the latter part of pregnancy, Vitamin K can result in toxicity in the newborn. Vitamin K. can counteract the effects of warfarin, a blood thinner, in patients requiring anticoagulation for their medical conditions.