- What is vitamin K? Vitamin K helps with proper blood clotting as well as with calcium utilization in bones and the cardiovascular system (See What It Does).
- Do you need to take vitamin K as a supplement? Most people are not deficient in vitamin K and symptomatic deficiency is rare, so unless you have a malabsorption condition or are severely malnourished, you likely get sufficient vitamin K from your diet (e.g., from green leafy vegetables, dairy, and fermented foods -- see Vitamin K from food). Vitamin K supplements have been clinically tested to increase bone density and reduce fractures, as well as to improve cardiovascular function, but results have been mixed, so it is not clear that supplementation will help (see What It Does).
- Which form of vitamin K is best? There are several forms of vitamin K. All are active, but one, the MK-7 form of vitamin K2, can increase blood levels of vitamin K up to 8 times as much as other forms. It's generally more expensive than the others, but it likely that you can take less of it (see What It Is and What to Consider When Buying).
- How much vitamin K to take? For adults, adequate daily intake of vitamin K is 90 mcg for women and 120 mcg for men. It is difficult to know what dose may be useful in bone health (or if any dose is truly beneficial). However, studies involving supplements containing K1 or the MK-4 form of K2 tend to use very high doses (e.g., 500 mcg to 45,000 mcg), while studies with the MK-7 form of K2 have used more moderate dosing, e.g., 180 mcg. (See What to Consider When Using).
- How to take vitamin K: Vitamin K is fat soluble, so you'll absorb more of it when you take it with a meal that has fats or oils. Other fat-soluble vitamins, like vitamin D, can compete with its absorption, so take them at least 3 hours apart. (See What to Consider When Using).
- Best choice of vitamin K? Products vary in quality and cost (See What CL Found). Among Approved products, ConsumerLab.com identified several which represented its Top Picks.
- Vitamin K safety and side effects: Vitamin K is fairly safe. However it can interact with certain medications. If you have an allergy to soy, be aware that most MK-7 forms of vitamin K are derived from soy, (See Concerns and Cautions). One branded form of MK-7 (MenaQ7) is derived from chickpeas and claims to be soy-free (See What It Does), although a product containing this form did not pass testing (See What CL Found).
Vitamin K Supplements Review (Including Calcium, Vitamin D, Magnesium & Boron)
Find the Best Vitamin K Supplement. Tests and Reviews of Popular Vitamin K Supplements & CL's Top Picks
Alphabetical list of vitamin K supplements compared in this review
Country Life Vegan K2
Dr. Mercola Vitamin K2
GNC Calcimate Complete
Healthy Origins Natural Vitamin K2 As MK-7
Innovix Labs Vitamin K2
Jarrow Formulas Bone-Up
Life Extension Vitamin D and K With Sea-Iodine
New Chapter Bone Strength take care
Relentless Improvement K2 Menatetrenone
Thorne Basic Bone Nutrients
Zhou K2 + D3
- Which vitamin K supplements failed our tests and which ones passed
- ConsumerLab.com's Top Picks among vitamin K supplements
- How to choose a vitamin K supplement that best suits your needs
- The difference in potency among the popular forms of vitamin K: vitamin K1 and two forms of vitamin K2 -- menaquinone-4 (MK-4) and menaquinone-7 (MK-7)
- The dose of vitamin K used for specific applications and how to best take it for maximum absorption
- How to get vitamin K from foods
- Potential drug interactions and side effects of vitamin K, including interactions with certain anticoagulants and soy allergy
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