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May occur as a result of
Deficient dietary intake (eg, green leafy vegetables and soybeans)
Malabsorption
Decreased production by intestinal bacteria (due to treatment with chemotherapy or antibiotics)
Vitamin K is required for normal function of vitamin K epoxide reductase that assists in posttranslational gamma-carboxylation of the coagulation factors II, VII, IX, and X, which is necessary for their activity
Risk of developing vitamin K deficiency is high in hospitalized patients taking broad-spectrum antibiotics who have poor or no oral intake
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Mild to moderate vitamin K deficiency typically features a prolonged prothrombin time (PT)
Severe vitamin D deficiency: prolonged activated partial thromboplastin time (aPTT)
Activity levels of individual clotting factors II, VII, IX, and X typically are low
Concomitant low factor V activity level not indicative of isolated vitamin K deficiency but may indicate an underlying defect in liver synthetic function
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