Menadione, is also known as vitamin K3, is a synthetic version of vitamin K. K1 and K2 are superior sources of vitamin K, which is needed for proper blood clotting. Menadion has never been researched or specifically approved for long term use, such as in pet food, has been banned from use in food and supplements for human use in many European countries due to serious side effects, and FDA has banned synthetic vitamin K from over-the-counter supplements because of its high toxicity. (www.dogfoodproject.com)