Vitamin K is a group of fat-soluble vitamins required for synthesis of the proteins needed for blood coagulation and for calcium binding in bones and other tissues.

These proteins undergo modification by vitamin K, which allows them to bind calcium ions. This is essential to control bleeding and without vitamin K, bleeding disorders occur. The bones may also become weak and the arteries and other tissues are susceptible to calcification.

People are generally able to get their daily requirement of vitamin K through a healthy and balanced diet and deficiency is rare. Furthermore, all fat-soluble vitamins such as vitamins A, D, E and K get stored in the body’s fat tissues and are eliminated at a much slower rate than water-soluble vitamins.

Although vitamin K deficiency does not generally occur in healthy adults, some risk factors for deficiency are describe below:

• Overuse of anticoagulants such as warfarin
• The use of barbiturates and salicylates
• Biliary tract disease can decrease fat absorption, leading to a deficiency in fat-soluble vitamins such as vitamin K. Examples include biliary stones, primary biliary cirrhosis and chronic cholestasis.
• Malabsorption can prevent proper intake of vitamin K. Examples of conditions where this may occur include Chron's disease, chronic pancreatitis, short bowel syndrome and ulcerative colitis.
• Diseases which involve the production of coagulation inhibitors such as paraproteinemias and myeloma may lead to vitamin K deficiency.
• The prolonged used of antibiotics can reduce the number of gut bacteria that synthesize vitamin K2.

Vitamin K deficiency in the newborn

Newborn babies are at risk of deficiency of vitamin K for several reasons, which include:

• Vitamin K does not cross the placenta to reach the fetus
• The sterile gut of the newborn means colonic bacterial synthesis of the vitamin is low
• Vitamin K level is low in breast milk

A breast-fed baby can be low in vitamin K for several weeks until their gut starts to develop the bacteria required to synthesize vitamin K2. These babies are at risk of a condition called hemorrhagic disease of the newborn, which can lead to severe bleeding that sometimes causes brain damage. As a preventative measure, babies are routinely given vitamin K injections after birth. Infant formula is made to contain vitamin K, but even babies who are fed this may be low in vitamin K for a few days after birth.