In later stages of deficiency, the other factors (which have longer half-lives) can "catch up," and the PTT also rises.

[citation needed] The prevalence of vitamin K deficiency varies by geographic region.

[2] Therefore, the Committee on Nutrition of the American Academy of Pediatrics recommends that 0.5 to 1.0 mg Vitamin K1 be administered to all newborns shortly after birth.

[4] Postmenopausal and elderly women in Thailand have a high risk of Vitamin K2 deficiency, compared with the normal value of young, reproductive females.

[7] Because colonic bacteria synthesize a significant portion of the Vitamin K required for human needs, individuals with disruptions to or insufficient amounts of these bacteria can be at risk for Vitamin K deficiency.