Protocols › Vitamin K

Vitamin K for bones

Goal: What trials of vitamin K1 and K2 used to slow bone loss after menopause, and why their results are mixed.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 3 Nov 2026
Dose

180 µg of MK-7 a day in a trial of 244 women.[1] Other trials gave 500 µg to 5 mg of vitamin K1 a day.[2][3] In Japan, 45 mg of MK-4 a day is used as a medicine for osteoporosis.[4]

Form

MK-7 capsules, vitamin K1 or MK-4. In two trials, both groups also got calcium and vitamin D.[5][2]

When to take

With a meal that contains some fat: vitamin K1 is absorbed together with fat from food.[6]

How long

1 to 4 years.[5][1][3]

What studies found

In 244 healthy women after menopause, 180 µg of MK-7 a day for 3 years slowed bone loss at the spine and the femoral neck, but not at the whole hip.[1] A 2019 review of 36 trials found no effect on bone density or spine fractures. It found 28% lower odds of any clinical fracture, but judged the evidence not enough to confirm this.[7]

Ask a doctor first

Vitamin K works against warfarin and similar blood thinners, so people who take them need a steady vitamin K intake.[4] The authors of one study warned that 50 µg of MK-7 a day or more may change the effect of these medicines.[8] No upper limit has been set for vitamin K.[4]

People who take a blood thinner or another medicine every day should ask a doctor or pharmacist first.[4]

References

  1. 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
  2. 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
  3. 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
  4. Vitamin K: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  5. 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
  6. Dietary reference values for vitamin K. European Food Safety Authority, 2017. efsa.onlinelibrary.wiley.com
  7. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Mott A, Bradley T, Wright K, Cockayne ES, Shearer MJ, Adamson J, et al. Osteoporos Int, 2019. PMID 31076817
  8. 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