Vitamin K Deficiency and Prothrombin Levels. Effect of Vitamin K Administration.

A detailed study was made concerning the rate at which the plasma prothrombin level falls when newly hatched chicks are placed on a vitamin K-deficient diet. The whole blood clotting time becomes prolonged when the prothrombin level falls to about 30% of the normal level for chicks of the same age. Hemorrhages make their appearance when the prothrombin is approximately 10% of normal.