was ist k3 vitamin — what are common causes?

Vitamin K3 (menadione) is a synthetic form of vitamin K not found naturally in foods. It is mainly used in animal feed because it can be converted to K2 in the body, but at higher doses it is toxic (hemolysis, liver damage). Therefore, it is banned in many countries for human supplements. The question 'what are common causes?' is ambiguous: if referring to vitamin K3 deficiency, there is no dietary deficiency since it is not a natural nutrient. General vitamin K deficiency (K1/K2) can result from malabsorption, antibiotics, liver disease, or warfarin use. If referring to causes of K3 exposure, it typically occurs through contaminated supplements or industrial use. The evidence is unclear because the question lacks specificity and no direct studies are provided in the given context. For personalized assessment, blood vitamin K levels and genetic factors (e.g., CYP4F2, VKORC1) are more relevant. Consult a doctor if uncertain.