What is it?
Vitamin K is a vitamin found in leafy green vegetables, broccoli, and Brussels sprouts. The name vitamin K comes from the German word “Koagulationsvitamin.”
Several forms of vitamin K are used around the world as medicine. Vitamin K1 (phytonadione) and vitamin K2 (menaquinone) are available in North America. Vitamin K1 is generally the preferred form of vitamin K because it is less toxic and works faster for certain conditions.
Vitamin K is most commonly used for blood clotting problems or for reversing the blood thinning effects of warfarin. It is also used for many other conditions, but there is no good scientific evidence to support most of these other uses.
Effective for …
- Bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease). Giving vitamin K1 by mouth or as a shot into the muscle helps prevent bleeding problems in newborns. Shots seem to work the best.
- Low levels of the blood clotting protein prothrombin (hypoprothrombinemia). Taking vitamin K1 by mouth or as an injection into the vein can prevent and treat bleeding problems in people with low levels of prothrombin due to using certain medications.
- A rare, inherited bleeding disorder (vitamin K-dependent clotting factors deficiency or VKCFD). Taking vitamin K by mouth or as an injection into the vein can help prevent bleeding in people with VKCFD.
- Reversing the blood thinning effects of warfarin. Taking vitamin K1 by mouth or as in injection into the vein can reverse too much blood thinning caused by warfarin. However, injecting vitamin K1 under the skin does not seem to work. Taking vitamin K along with warfarin also seems to help stabilize blood clotting time in people taking warfarin. It works best in people who have low vitamin K levels.
Possibly Effective for …
- Weak and brittle bones (osteoporosis). Taking a specific form of vitamin K2 seems to improve bone strength and reduce the risk of fracture in most older women with weak bones. But it doesn’t seem to benefit older women who still have strong bones. Taking vitamin K1 seems to increase bone strength and might prevent fractures in older women. But it might not work as well in older men. Vitamin K1 doesn’t seem to improve bone strength in women who have not gone through menopause or in people with Crohn disease.
Possibly Ineffective for …
- Bleeding into or around the fluid-filled areas (ventricles) of the brain (intraventricular hemorrhage). Giving vitamin K to women at risk for very preterm births does not seem to prevent bleeding in the brain of preterm infants. It also doesn’t seem to reduce the risk of nerve injury caused by these bleeds.
Insufficient Evidence to Make a Determination for …
- Athletic performance. Early research suggests that taking vitamin K2 by mouth might improve exercise performance by increasing the work of the heart.
- A blood disorder that reduces levels of protein in the blood called hemoglobin (beta-thalassemia). Early research shows that taking vitamin K2 by mouth along with calcium and vitamin D can improve bone mass in children with this blood disorder.
- Breast cancer. Research suggests that higher dietary intake of vitamin K2 is linked with a lower risk of developing breast cancer.
- Cancer. Some research has linked a higher food intake of vitamin K2, but not vitamin K1, with a reduced risk of death from cancer. But other research has linked a higher food intake of vitamin K1, but not vitamin K2, with a reduced risk of death from cancer.
- Cataracts. Some research has linked a higher food intake of vitamin K2 with a lower risk of getting cataracts.
- Colon cancer, rectal cancer. Early research suggests that a higher dietary intake of vitamin K is not linked with a reduced risk of cancer of the colon and rectum.
- Heart disease. Most research shows that higher dietary intake of vitamin K1 and K2 is linked with a reduced risk of heart disease. But higher dietary intake of vitamin K1 doesn’t seem to reduce the risk of dying from heart disease in general.
- Cystic fibrosis. People with cystic fibrosis have low levels of vitamin K due to problems digesting fat. Taking vitamin K increases vitamin K levels. But it is unclear if it prevents problems with blood clotting and bone growth in these people.
- Depression. Early research has found that higher intake of vitamin K from food is linked with a lower risk for depression. But there isn’t any research on whether taking vitamin K supplements can reduce the risk of depression.
- Diabetes. Early research shows that taking a multivitamin fortified with vitamin K1 does not lower the risk of developing diabetes compared to taking a regular multivitamin.
- Acne-like rash caused by certain cancer drugs. People who are given a certain type of anticancer medicine often develop skin rash. Early research shows that applying a cream containing vitamin K1 helps prevent skin rash in people being given this type of medicine. But other research shows that using an ointment with vitamin K does not improve this rash in people that have already developed it.
- High cholesterol. There is early evidence that vitamin K2 might lower cholesterol in people on dialysis with high cholesterol levels.
- Liver cancer. Taking vitamin K2 does not seem to prevent liver cancer recurrence. But some early research shows that taking vitamin K2 reduces the risk of liver cancer in people with liver cirrhosis.
- Liver disease. Injecting vitamin K into the muscle has been linked with lower risk of death in people with liver failure.
- Lung cancer. Early research suggests that higher intake of vitamin K2 from food is linked with a reduced risk of lung cancer and lung cancer-related death. Dietary intake of vitamin K1 does not seem to be linked with a reduced risk of these events.
- Multiple sclerosis (MS). Interferon is a medicine that helps people with MS. This medicine often causes a rash and burning of the skin. Early research shows that applying vitamin K cream modestly reduces rash and burning in people treated with interferon.
- Death from any cause. Low intake of vitamin K might be linked to higher risk of death in healthy older adults.
- Prostate cancer. Early research has found that higher dietary intake of vitamin K2, but not vitamin K1, is linked with a reduced risk of prostate cancer.
- Rheumatoid arthritis (RA). Early research shows that taking vitamin K2 along with arthritis medicine reduces markers of joint swelling better than taking arthritis medicine alone. But taking vitamin K1 does not seem to reduce symptoms of RA.
- Stroke. Population research has found that dietary intake of vitamin K1 is not linked with a reduced risk of stroke.
- Spider veins.
- Stretch marks.
- Other conditions.
More evidence is needed to rate vitamin K for these uses.
When applied to the skin: Vitamin K1 is POSSIBLY SAFE for most people when applied as a cream that contains 0.1% vitamin K1.
When given by IV: The two forms of vitamin K (vitamin K1 and vitamin K2) are LIKELY SAFE for most people when injected into the vein appropriately.
Special Precautions & Warnings:
Pregnancy and breast-feeding: When taken in the recommended amount each day, vitamin K is LIKELY SAFE for pregnant and breast-feeding women. Don’t use higher amounts without the advice of your healthcare professional.
Children: The form of vitamin K known as vitamin K1 is LIKELY SAFE for children when taken by mouth or injected into the body appropriately.
Kidney disease: Too much vitamin K can be harmful if you are receiving dialysis treatments due to kidney disease.
Liver disease: Vitamin K is not effective for treating clotting problems caused by severe liver disease. In fact, high doses of vitamin K can make clotting problems worse in these people.
Reduced bile secretion: People with decreased bile secretion who are taking vitamin K might need to take supplemental bile salts along with vitamin K to ensure vitamin K absorption.
Interaction Rating=Major Do not take this combination.
Vitamin K is used by the body to help blood clot. Warfarin (Coumadin) is used to slow blood clotting. By helping the blood clot, vitamin K might decrease the effectiveness of warfarin (Coumadin). Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
Tiratricol: There is a concern that tiratricol might interfere with vitamin K’s role in blood clotting.
Vitamin A: In animals, high doses of vitamin A interfere with vitamin K’s ability to clot blood. But it’s not known if this also happens in people.
Vitamin E: High doses of vitamin E (e.g. greater than 800 units/day) can make vitamin K less effective in clotting blood. In people who are taking warfarin to keep their blood from clotting, or in people who have low vitamin K intakes, high doses of vitamin E can increase the risk of bleeding.
- For weak and brittle bones (osteoporosis): The MK-4 form of vitamin K2 has been taken in doses of 45 mg daily. Also, vitamin K1 has been taken in doses of 1-10 mg daily.
- For a rare, inherited bleeding disorder (vitamin K-dependent clotting factors deficiency or VKCFD): 10 mg of vitamin K has been taken 2-3 times weekly.
- For reversing the blood thinning effects of warfarin: A single dose of 1-5 mg of vitamin K1 is typically used to reverse the effects of taking too much warfarin. The exact dose needed is determined by a lab test called the INR. Daily doses of 100-200 micrograms of vitamin K have been used for people taking warfarin long-term who have unstable blood clotting.
WITH A NEEDLE:
- For a rare, inherited bleeding disorder (vitamin K-dependent clotting factors deficiency or VKCFD): 10 mg of vitamin K has been injected into the vein. How often these injections are given is determined by a lab test called the INR.
- For reversing the blood thinning effects of warfarin: A single dose of 0.5-3 mg of vitamin K1 is typically used. The exact dose needed is determined by a lab test called the INR.
- For bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease): 1-2 mg of vitamin K1 has been given in three doses over 8 weeks. Also single doses containing 1 mg of vitamin K1, 5 mg of vitamin K2, or 1-2 mg of vitamin K3 have been used.
WITH A NEEDLE:
- For bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease): 1 mg of vitamin K1 has been given as a shot into the muscle.
There isn’t enough scientific information to determine recommended dietary allowances (RDAs) for vitamin K, so daily adequate intake (AI) recommendations are used instead: The AIs are: infants 0-6 months, 2 mcg; infants 7-12 months, 2.5 mcg; children 1-3 years, 30 mcg; children 4-8 years, 55 mcg; children 9-13 years, 60 mcg; adolescents 14-18 years (including those who are pregnant or breast-feeding), 75 mcg; men over 19 years, 120 mcg; women over 19 years (including those who are pregnant and breast-feeding), 90 mcg.
Natural Medicines disclaims any responsibility related to medical consequences of using any medical product. Effort is made to ensure that the information contained in this monograph is accurate at the time it was published. Consumers and medical professionals who consult this monograph are cautioned that any medical or product related decision is the sole responsibility of the consumer and/or the health care professional. A legal License Agreement sets limitations on downloading, storing, or printing content from this Database. Except for any possible exceptions written into your License Agreement, no reproduction of this monograph or any content from this Database is permitted without written permission from the publisher. Unlawful to download, store, or distribute content from this site.
For the latest comprehensive data on this and every other natural medicine, health professionals should consult the Professional Version of the Natural Medicines. It is fully referenced and updated daily.
© Copyright 1995-2021. Therapeutic Research Faculty, publishers of Natural Medicines, Prescriber’s Letter, and Pharmacist’s Letter. All rights reserved.