Vitamin K has two forms:
Phylloquinone: This form occurs in plants and is consumed in the diet. It is absorbed better when it is consumed with fat. Phylloquinone is not toxic, even in large amounts.
Menaquinone: This form is produced by bacteria in the intestine, but only small amounts of it are produced. In some countries, this form is used for supplementation.
Vitamin K is necessary for normal blood clotting. It is also needed for healthy bones and other tissues.
The effects of vitamin K toxicity can include anemia due to rupture of red blood cells and jaundice. Jaundice in newborns can cause kernicterus (a type of brain damage).
(See also Overview of Vitamins.)