Lets discuss the function of Vitamin K first:

1. The most important function of vitamin K is that it helps in the formation of prothrombin. A decrease in plasma prothrombin level is seen in deficiency of vitamin K
2. It appear to some role in electron transport system because its structure is similar to coenzyme Q. In plant Kingdom vitamin K1 is an essential component of the photosynthetic process.

   Effects of Deficiency of Vitamin K

There are due to a lower level of prothrombin and some other factors need for normal blood clotting mechanism. There is an increase in the prothrombin time showing a deficiency of prothrombin and clotting time is prolonged, with a tendency to bleed profusely from minor wounds. Bleeding occurs mainly from the gastrointestinal tract, urinary tract and the uterus.

Condition associated with Vitamin K deficiency

Many conditions are associated with a deficiency of vitamin K and lead to bleeding tendencies by producing hypoprothrombinemia. These includes the following

1. Faculty absorption of Vitamin K due to lack of bile as occurs in obstructive Jaundice and biliary fistula. Water Soluble preparation of Vitamin K can, however, be absorbed in the absence of the bile salts.
2. Diarrheal diseases, e.g. sprue, celiac disease and ulcerative colitis interfere with absorption of Vitamin K. Administration of mineral oil (liquid paraffin) over prolonged periods has also the same effect.
3. Administration of broad spectrum antibiotics: These drugs kill the normal flora of the intestine and stop the synthesis of Vitamin K.
4. In new-born babies especially premature ones: Vitamin K does not easily cross placental barrier. Moreover, the bowels of a new born are sterile and thus no vitamin K can be formed within them. This results in physiological hypoprothrombinemia of the new-born. However, Vitamin K should not be given to the new-born babies as a routine because toxic effect like hemolytic anemia, hyper-bilirubinemia, hepatomegaly and death have occurred in some cases.
5. Administration of drugs having anti-vitamin K activity: The anticoagulant drug bishydroxycoumarin and large doses of salicyclates exert an anti-vitamin K effect and produce hypoprothrombinemia. Vitamin K reverses the effects of these drugs. Vitamin K3 is ineffective in reversing the effects of bishydroxycoumarin.

In addition to the above-mentioned conditions in which hypoprothrombinemia is due to a lack of vitamin K, extensive liver disease will also result in a low plasma prothrombin level. Vitamin K will not improve this type of Hypoprothrombinemia because liver cells themselves are diseased and cannot synthesize.

Human requirements: Not established,  normally there is sufficient vitamin K in the diet which is also supplemented by the intestinal synthesis. Its storage occurs to a limited extent only.