Vitamin K

Is vitamin K2 better than vitamin K1?

Updated 3 Nov 2026

Short answer

It is not proven. MK-7, a form of vitamin K2, stays in the blood longer than vitamin K1. In healthy volunteers, it built up to higher levels with daily intake and activated more osteocalcin.[1] But two trials that compared vitamin K1 with MK-4 found that neither changed bone density more than placebo.[2][3]

The forms

  • Vitamin K1 (phylloquinone) is the main form in food and comes mostly from green leafy vegetables. Phytonadione is its synthetic form, used in supplements.[4]
  • MK-4, a vitamin K2, is made by the body from vitamin K1. Meat, eggs and cheese contain small amounts.[4] In Japan, 45 mg of MK-4 a day is a medicine for osteoporosis.[4]
  • MK-7, another vitamin K2, comes from bacteria. Natto, fermented soybeans, has 850 µg in 3 ounces.[4]
  • Vitamin K3 (menadione) is synthetic. It is no longer used in supplements, because it damaged liver cells in lab studies.[4]

How K1 and MK-7 differ in the body

In a study in healthy volunteers, both vitamin K1 and MK-7 were absorbed well, with the highest blood level 4 hours after intake.[1] MK-7 left the blood much more slowly. During daily intake, its blood level stayed more stable and built up to much higher levels, and it activated more osteocalcin.[1]

EFSA notes that MK-7 may be more active than vitamin K1, but the data are not enough to give each form its own value. It set intake values for vitamin K1 only.[5]

Trials that compared two forms

  • 381 healthy North American women after menopause took 1 mg of vitamin K1, 45 mg of MK-4 or a placebo for 12 months. Both forms lowered unfinished osteocalcin, and neither changed bone density.[2]
  • 105 women after menopause with osteoporosis and low vitamin K1 levels took 1 mg of vitamin K1, 45 mg of MK-4 or a placebo for 18 months. They all also took a bisphosphonate with calcium or vitamin D. Bone density did not differ. Vitamin K1 had a small effect on some measures of hip shape.[3]

Doses differ between forms

Trials of MK-7 gave 180 to 720 µg a day.[6][7] Trials of MK-4 gave 45 mg a day.[2][3] Trials of vitamin K1 gave 500 µg to 5 mg a day.[8][9]

What is still unknown

There are few data on how well the different supplement forms are absorbed.[4] EFSA found too little data on the absorption, function and body content of menaquinones to set an intake value for them.[5] It is also unclear how much of the vitamin K2 made by gut bacteria the body can use.[4][5]

Who should be careful

People who take warfarin or a similar blood thinner should ask a doctor or pharmacist first.[4] MK-7 stays in the blood a long time, and the authors of one study warned that 50 µg a day or more may change their effect.[1]

Sources (9)

  1. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Schurgers LJ, Teunissen KJ, Hamulyák K, Knapen MH, Vik H, Vermeer C Blood, 2007. PMID 17158229
  2. Vitamin K treatment reduces undercarboxylated osteocalcin but does not alter bone turnover, density, or geometry in healthy postmenopausal North American women. Binkley N, Harke J, Krueger D, Engelke J, Vallarta-Ast N, Gemar D, et al. J Bone Miner Res, 2009. PMID 19113922
  3. The additive effect of vitamin K supplementation and bisphosphonate on fracture risk in post-menopausal osteoporosis: a randomised placebo controlled trial. Moore AE, Dulnoan D, Voong K, Ayis S, Mangelis A, Gorska R, et al. Arch Osteoporos, 2023. PMID 37338608
  4. Vitamin K: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  5. Dietary reference values for vitamin K. European Food Safety Authority, 2017. efsa.onlinelibrary.wiley.com
  6. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Knapen MH, Drummen NE, Smit E, Vermeer C, Theuwissen E Osteoporos Int, 2013. PMID 23525894
  7. Vitamin K2 and D in Patients With Aortic Valve Calcification: A Randomized Double-Blinded Clinical Trial. Diederichsen ACP, Lindholt JS, Möller S, Øvrehus KA, Auscher S, Lambrechtsen J, et al. Circulation, 2022. PMID 35465686
  8. Effect of vitamin K supplementation on bone loss in elderly men and women. Booth SL, Dallal G, Shea MK, Gundberg C, Peterson JW, Dawson-Hughes B J Clin Endocrinol Metab, 2008. PMID 18252784
  9. Vitamin K supplementation in postmenopausal women with osteopenia (ECKO trial): a randomized controlled trial. Cheung AM, Tile L, Lee Y, Tomlinson G, Hawker G, Scher J, et al. PLoS Med, 2008. PMID 18922041

More about vitamin k

What is vitamin K?Which foods contain vitamin K?What is vitamin K used for?Who is at risk of vitamin K deficiency?Is vitamin K safe?Why do newborn babies get vitamin K?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.