Vitamin K is essential in the formation of coagulation factors, which are substances that help the blood form clots to prevent excessive bleeding. It is also believed to play a role in preventing bone loss.

There are different forms of vitamin K; K1 is the natural form present in foods such as green vegetables, dairy products, breakfast cereals, vegetable oils and soybeans. A diet with appropriate amounts of vitamin K is important because the body is not able to produce an adequate amount on its own. The average American diet supplies a sufficient level, but conditions such as obstructive liver disease, obstructive icterus and malabsorption (often a result of Celiac disease, pancreatitis, diarrhea and antibiotic abuse) can lead to a deficiency.

Vitamin K deficiency can result in excessive bleeding and bruising. Often the first test recommended for patients with such symptoms is a combination PT & PTT Blood Test, which measures how long it takes for the blood to form a clot. If a prolonged result is the outcome and a vitamin K deficiency is suspected, treatment typically involves injections or supplements of the vitamin. If this resolves the unexpected bleeding and the next test is normal, vitamin K deficiency is assumed to have been the cause.