Vitamin K1 is also known as phylloquinone and is a fat-soluble vitamin naturally found in a large number of green plants, including broccoli, kale, Brussels sprouts and other members of the Brassica group. It plays a major role in proper blood clotting and can be used medicinally to treat bleeding caused by medications or illness. It can also prevent and treat osteoporosis and some side effects of liver disease. When applied topically, vitamin K1 can treat rosacea, stretch marks, burns, scars, bruises and spider veins. 

Low levels of vitamin K1 can produce a range of bleeding and bruising problems, especially at surgical sites or around other wounds. People with a deficiency in this vitamin can also have cartilage calcification, stomach pain and deformed developing bone. Narrowing of the arteries due to deposits of insoluble calcium salts is also common. Doctors rarely order vitamin K1 blood tests, however. This is because most cases of vitamin K deficiency are detected via their symptoms, rather than through laboratory testing. 

When doctors do use a test for vitamin K in the bloodstream, it is usually to investigate the cause of excessive bleeding. Prothrombin time tests, or PT tests, are usually used for this purpose. The blood sample for these tests should be collected before taking any blood thinners or coagulants, but NO FASTING is required. Consumption of foods containing a large amount of vitamin K shortly before the test could skew the results and should be avoided.