Vitamin K is required for normal blood clotting (its name is derived from the German word ‘koagulation’). It is essential to the formation in the liver of prothrombin, which converts into thrombin thereby initiating blood coagulation and the conversion of fibrinogen into fibrin (the primary protein in blood clots). Vitamin K is also needed to manufacture other blood clotting compounds – Factor VII, Factor IX and Factor X. These clotting compounds are dependent on vitamin K’s role in the production of carboxyglutamate residues. The so-called ‘coagulation cascade’ associated with these and several other clotting factors is needed not only to coagulate and clot blood, but also to form a ‘scab’ at sites of tissue injury to prevent excessive blood loss. Due to its wide dietary availability and synthesis by intestinal bacteria, vitamin K deficiency is not common in adults. However, new-born babies are prone to low prothrombin levels due to poor placental transmission of fats and lack of digestive bacteria. As a result, in order to prevent haemorrhage it is not uncommon for expectant mothers to be prescribed vitamin K (as Kl) for several days before delivering and for babies to be given vitamin K (as Kl) for a short time, i.e. in periodic doses over a 1-3 month period after delivery.