Present knowledge shows that vitamin K deficiency is uncommon in healthy adults because vitamin K is widespread in foods (see Sources).
Adults at risk of vitamin K deficiency include those taking vitamin K antagonist blood clotting inhibiting (‘anticoagulant’) drugs and individuals with significant liver damage or disease (5). Additionally, individuals with poor absorption of fat from food (‘fat malabsorption’) may be at increased risk of vitamin K deficiency(3).
Newborn babies who are exclusively breast-fed are at increased risk of vitamin K deficiency, partly because human milk is relatively low in vitamin K compared to formula and newborn infants, in general, have low vitamin K status (3).
Overt vitamin K deficiency results in impaired blood clotting, usually demonstrated by laboratory tests that measure clotting time. Symptoms include easy bruising and bleeding that may be manifested as nosebleeds, bleeding gums, blood in the urine, blood in the stool, tarry black stools or extremely heavy menstrual bleeding. In infants, vitamin K deficiency may result in life-threatening bleeding within the skull (‘intracranial hemorrhage’) (5).
Vitamin K deficiency in newborns may result in a bleeding disorder called ‘vitamin K deficiency bleeding’ (VKDB) of the newborn. Because VKDB is life-threatening and easily prevented, a number of international organizations recommend that vitamin K1 (phylloquinone) be administered to all newborns (31).
In the early 1990s, two retrospective studies were published suggesting a possible association between vitamin K injections in newborns and the development of childhood leukemia and other forms of childhood cancer. However, two large retrospective studies in the United States and Sweden that reviewed the medical records of 54,000 and 1.3 million children, respectively, found no evidence of a relationship between childhood cancers and vitamin K injections at birth (32, 33). As VKDB is life-threatening and the risks of cancer are unproven and unlikely, many pediatricians recommend routine vitamin K prophylaxis for newborns (34). Recently, paediatricians observed an increase in the number of late-onset cases of VKDB due to the popular trend of parental refusal of newborn vitamin K prophylaxis (41).
Study findings in premature infants (35, 36) have led some experts to suggest the use of an initial vitamin K1 dose of 0.3 mg/kg for infants with birth weights under 1,000 g, and a standard initial dose of 1.0 mg vitamin K1 for full-term infants to prevent hemorrhagic disease (35).
Authored by Dr Peter Engel in 2010, reviewed and updated by Dr Szabolcs Peter on 18.06.2017