Vitamin K

by MedlinePlus

Forms of vitamin K: The name "Vitamin K" refers to a group of chemically similar fat-soluble compounds called naphthoquinones. Vitamin K1 (phytonadione) is the natural form of vitamin K, which is found in plants, and provides the primary source of vitamin K to humans through dietary consumption. Vitamin K2 compounds (menaquinones) are made by bacteria in the human gut, and provide a smaller amount of the human vitamin K requirement. Vitamin K1 is commercially manufactured for medicinal use under several brand names (Phylloquinone, Phytonadione, AquaMEPHYTON, Mephyton, Konakion). A water-soluble preparation is available for adults only as vitamin K3 (menadione).

Natural sources: Vitamin K is found in green leafy vegetables like spinach, broccoli, asparagus, watercress, cabbage, cauliflower, green peas, beans, olives, canola, soybeans, meat, cereals, and dairy products. Cooking does not remove significant amounts of vitamin K from these foods. People who eat a balanced diet including these foods are likely ingesting enough vitamin K and do not require supplementation.

Blood clotting: Vitamin K is necessary for normal clotting of blood in humans. Specifically, vitamin K is required for the liver to make factors that are necessary for blood to properly clot (coagulate), including factor II (prothrombin), factor VII (proconvertin), factor IX (thromboplastin component), and factor X (Stuart factor). Other clotting factors that depend on vitamin K are protein C, protein S, and protein Z. Deficiency of vitamin K or disturbances of liver function (for example, severe liver failure) may lead to deficiencies of clotting factors and excess bleeding. For example, if prothrombin levels fall to 10-15% of normal levels, bleeding may occur even with minor traumas. If prothrombin levels fall beneath 10%, potentially serious spontaneous bleeding (hemorrhage with no clear cause) may occur.

Deficiency: Vitamin K deficiency is rare, but can lead to defective blood clotting and increased bleeding. People at risk for developing vitamin K deficiency include those with chronic malnutrition (including those with alcohol dependency), or conditions which limit absorption of dietary vitamins such as biliary obstruction, celiac disease or sprue, ulcerative colitis, regional enteritis, cystic fibrosis, short bowel syndrome or intestinal resection (particularly of the terminal ileum, where fat-soluble vitamins are absorbed). In addition, some drugs may reduce vitamin K levels by altering liver function or by killing intestinal flora (normal intestinal bacteria) that make vitamin K (for example, antibiotics, salicylates, anti-seizure medications, and some sulfa drugs). Vitamin K is routinely given to newborn infants to prevent bleeding problems related to birth trauma or when surgery is planned.

Warfarin (Coumadin): Warfarin is a blood-thinning drug that functions by inhibiting vitamin K-dependent clotting factors. Warfarin is prescribed by doctors for people with various conditions such as atrial fibrillation, artificial heart valves, history of serious blood clot, clotting disorders (hypercoagulability), or placement of indwelling catheters/ports. Usually, blood tests must be done regularly to evaluate the extent of blood thinning, using a test for prothrombin time (PT) or International Normalized ratio (INR). Vitamin K can decrease the blood thinning effects of warfarin, and will therefore lower the PT or INR value. This may increase the risk of clotting. Therefore, people taking warfarin are usually warned to avoid foods with high vitamin K content (such as green leafy vegetables), and to avoid vitamin K supplements. Conversely, vitamin K is used to treat overdoses or excess anticoagulant effects of warfarin, or to reverse the effects of warfarin prior to surgery or other procedures.

Synonyms

2-methyl-1,4-naphthoquinone, AquaMEPHYTON, Konakion, Menadiol (not available in U.S.), menadione, menaquinones, menatetrenone, Mephyton, Phylloquinone, Phytomenadione, Phytonadione.

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidence

Vitamin K deficiency

Adults: Vitamin K deficiency is rare in adults, but can lead to defective blood clotting and increased bleeding, as well as osteoporosis. People at risk for developing vitamin K deficiency include those with chronic malnutrition (including those with alcohol dependency), or conditions which limit absorption of dietary vitamins such as biliary obstruction, celiac disease or sprue, ulcerative colitis, regional enteritis, cystic fibrosis, short bowel syndrome or intestinal resection (particularly of the terminal ileum, where fat-soluble vitamins are absorbed). In addition, some drugs may reduce vitamin K levels by altering liver function or by killing intestinal flora (normal intestinal bacteria) that make vitamin K (for example, antibiotics, salicylates, anti-seizure medications, and some sulfa-drugs). Evaluation by a physician should be sought, and blood tests for prothrombin time (PT) and activated partial thromboplastin time (aPTT) should be followed by a work-up to find the potential cause(s). Blood levels of vitamin K can be measured in adults (but are not useful in infants in whom levels are usually low).As treatment, vitamin K1 (Phylloquinone, Phytonadione, AquaMEPHYTON, Mephyton, Konakion) can be given by injection. Subcutaneous injection is preferred, because life-threatening allergic reactions have been rarely associated with intravenous and intramuscular administration, and hematomas (bruises) can occur with intramuscular injection. Vitamin K can also be given by mouth in less urgent cases. If the PT is only slightly elevated and poor dietary intake is thought to be the cause, increasing the ingestion of vitamin K-rich foods can be tried. During treatment, blood tests for PT should be followed to check for normalization. If the PT does not correct, causes such as severe liver disease or disseminated intravascular coagulation (DIC) should be considered by a physician. In urgent situations, a dilution of vitamin K can be given intravenously, although there is a risk of serious allergic/anaphylactoid reactions. In cases of life-threatening bleeding, hospitalization and treatment with fresh frozen plasma (FFP) may be necessary.Newborns/Infants: See below discussion of "Hemorrhagic disease of newborn (vitamin K deficiency bleeding/VKDB)."

Warfarin reversal (elevated INR / pre-procedure)

Warfarin toxicity (elevated PT/INR): Warfarin is a blood-thinning drug that inhibits vitamin K-dependent clotting factors. Warfarin is prescribed by doctors for people with various conditions such as atrial fibrillation, artificial heart valves, history of serious blood clot, clotting disorders (hypercoagulability), or placement of indwelling catheters/ports. Usually, blood tests are done regularly to evaluate the extent of blood thinning, using a test for prothrombin time (PT) or International Normalized ratio (INR). The range for the PT/INR depends on the condition being treated. The PT/INR can become elevated for many reasons, and sometime can get dangerously high and increase the risk of serious bleeding. Patients taking warfarin should be aware of these potential causes, which include many drugs that interact with warfarin, liver disorders, or accidental warfarin overdose. Because the effects of warfarin on anticoagulation are usually delayed by several days, the PT/INR may not increase immediately at the time of overdose.Management should be under strict medical supervision. Generally, if the INR is higher than intended but less than 6, and the patient is not bleeding, then warfarin can be held for 2-3 days then restarted when the range is acceptable. If the INR is 6-10 without bleeding, then 1-2mg of vitamin K1 can be given subcutaneously. If the INR is greater than 10 without bleeding, then 3mg of vitamin K1 (Phylloquinone, Phytonadione, AquaMEPHYTON, Mephyton, Konakion) can be administered subcutaneously. In cases of serious bleeding or very high INR (greater than 20), 10mg of vitamin K1 can be given subcutaneously with fresh frozen plasma or prothrombin complex concentrate.Pre-procedure: The need for anticoagulation reversal before a procedure should be discussed with the overseeing medical team. The principal concern is to reduce the risk of excess bleeding during the procedure that may occur due to warfarin anticoagulation, but also not to increase the risk of clotting due to stopping warfarin for an extended period. Vitamin K is occasionally used to reverse warfarin before surgical procedures, although high doses are generally avoided because of the resulting delay in re-anticoagulation after the procedure.For minor procedures such as tooth extractions, some eye operations, or biopsies, reversal may not be necessary if the INR is 2.5 or lower. For more serious procedures, the approach depends on the initial reason for anticoagulation. For patients taking warfarin for prosthetic heart valves, the warfarin can be held for four days prior to surgery while the patient is given low-molecular-weight heparin for up to 12 hours before the procedure. Warfarin can be restarted after surgery. For patients with atrial fibrillation or cardiomyopathy, warfarin can be held for four days prior to surgery, and then restarted afterwards. In high-risk patients with a history of deep venous thrombosis (DVT) or a pulmonary embolus (PE), after warfarin is held, intravenous unfractionated heparin coverage can be given until six hours before surgery, then restarted 12 hours after surgery. Warfarin can then be restarted.More aggressive measures may be necessary in patients with recent or multiple past blood clots. In patients with a history of an arterial clot, warfarin can be held for four days, and the INR can be checked on the day before surgery. If the INR is greater than 1.7, then 1mg of vitamin K can be given subcutaneously. On the day of surgery, if the INR is still elevated, fresh frozen plasma should be administered.

Hemorrhagic disease of newborn (vitamin K deficiency bleeding / VKDB)

Vitamin K deficiency in infants can lead to hemorrhagic disease of the newborn, also known as vitamin K deficiency bleeding (VKDB). There are three time frames in which VKBD can occur, depending on the underlying cause: early-onset within 24-hours of birth (rare, usually due to vitamin K deficiency in the mother or poor transmission of vitamin K across the placenta); classic onset (2-7 days, usually in breastfeeding infants since infant formulas are usually supplemented with vitamin K); and late-onset (after 2 weeks of age, often in infants with cystic fibrosis, hepatitis, celiac disease, persistent diarrhea, malabsorption, lack of bacteria in the intestines/sterile gut, or alpha-1 antitrypsin deficiency). Although up to half of newborns may have some degree of vitamin K deficiency, serious hemorrhagic disease with bleeding is rare.Prophylaxis (prevention): Because vitamin K given by injection has been shown to prevent VKBD in newborns and young infants, the American Academy of Pediatrics recommends administering a single intramuscular injection of 0.5 to 1mg of vitamin K1 to all newborns. Oral dosing is not considered adequate as prevention, particularly in breastfeeding infants. Initial concerns of cancer risk were never proven, and are generally not considered clinically relevant.Treatment: In cases of true VKDB, bleeding may occur at injection sites, at the umbilicus, or in the gastrointestinal tract. Life-threatening bleeding into the head (intracranial) or in the area behind the lower abdomen (retroperitoneum) can also occur. Evaluation by a physician is imperative, and blood tests for prothrombin time (PT) and activated partial thromboplastin time (aPTT) should be done followed by a work-up to find the potential cause(s). Blood levels of vitamin K are not useful, because levels are usually low in infants. Vitamin K1 can be given by injection. Subcutaneous administration is preferred, because hematomas can occur with intramuscular injections, and intravenous administration carries a risk of serious allergic (anaphylactoid) reactions.

Osteoporosis prevention

Vitamin K appears to prevent bone resorption, and adequate dietary intake is likely necessary to prevent excess bone loss. Elderly or institutionalized patients may be at particular risk, and adequate intake of vitamin K-rich foods should be maintained. Unless patients have demonstrated vitamin K deficiency, there is no evidence that additional vitamin K supplementation is helpful. However, vitamin K may play a role in the prevention and treatment of glucocorticoid-induced bone loss. Further research is needed to confirm these results.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Cancer, celiac disease, cystic fibrosis, liver function testing, osteoporosis treatment.

About the Author

medlineplus.gov
MedlinePlus will direct you to information to help answer health questions. MedlinePlus brings together authoritative information from NLM, the National Institutes of Health (NIH), and other government agencies and health-related organizations. MedlinePlus also has extensive information about drugs, an illustrated medical encyclopedia, interactive patient tutorials, and latest health news.