Newborns are routinely given vitamin K at the time of birth. Babies normally have low levels of vitamin K until they are able to manufacture it in their systems. Vitamin K is one of the blood clotting factors which is produced by normal intestinal bacteria. On rare occasions, this transitory condition can lead to bleeding in approximately 1/10,000 babies. For preventive measures, newborns have been receiving Vitamin K routinely since the 1960s. Traditionally vitamin K has been given as a shot. However, studies show that vitamin K given orally is just as effective in healthy infants.

Infants who are born prematurely, delivered with complications such as forceps, or those who have liver conditions are at higher risk from bleeding. Also babies whose mothers took epilepsy medication during pregnancy. Vitamin K deficiency can result in early bleeding in the first week of life (0.4%-1.7% of newborns) or 2-12 weeks of age in almost exclusively breast fed infants.(reports vary from 4.4 to 10.5 in every 100,000 births) This is due to the fact that mother's milk is low in vitamin K (baby formula contains vitamin K). However, substances in breast milk help baby build up enough normal digestive bacteria which are needed to produce vitamin K. Formula fed babies take longer to build up the necessary bacteria because of its processed nature.