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Vitamin k2

Supplement vitamin bone & jointheart & metabolic
Aka: menaquinone, MK-7, MK-4, vitamin K
Brands seen in Singapore: California Gold Nutrition, Futurebiotics, Sports Research, Thorne, NOW Foods
Third-party tested: Sports Research, Thorne certify other products with NSF Certified for Sport, but nothing for vitamin k2.Certification is granted per product, so check the tub you actually own. Not being listed is not the same as failing.
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Coenzyme for clotting and bone-metabolism proteins
When to take
No timing rule
Take with
Fat-soluble · absorbed like dietary fat, via bile
Pros & cons
Pros
  • No UL — fnb found no reported adverse effects
  • One RCT: mk-7 180 mcg/day × 3 y improved bone strength
  • Meta-analysis: higher lumbar-spine bmd after menopause
Cons
  • On warfarin? a serious clash — steady intake matters
  • Artery calcification / heart evidence still unclear
  • SG: k capped at 0.12 mg, in multi-vitamin products only
Sources
  1. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Introduction · read 2026-08-27
    what it says
    “These compounds include phylloquinone (vitamin K1) and a series of menaquinones (vitamin K2) … Vitamin K functions as a coenzyme for vitamin K-dependent carboxylase, an enzyme required for the synthesis of proteins involved in hemostasis (blood clotting) and bone metabolism”
  2. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Introduction (absorption) · read 2026-08-27
    what it says
    “Like dietary lipids and other fat-soluble vitamins, ingested vitamin K is incorporated into mixed micelles via the action of bile and pancreatic enzymes, and it is absorbed by enterocytes of the small intestine”
  3. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Table 1 Adequate Intakes + DV note · read 2026-08-27
    what it says
    “Insufficient data were available to establish an EAR for vitamin K, so the FNB established AIs … Table 1: Adequate Intakes (AIs) for Vitamin K … 19+ years 120 mcg 90 mcg … The DV for vitamin K is 120 mcg for adults”
  4. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Dietary supplements · read 2026-08-27
    what it says
    “Vitamin K is present in most multivitamin/mineral supplements, typically at values less than 75% of the DV … some providing 4,050 mcg … both phytonadione and MK-7 supplements are well absorbed, but MK-7 has a longer half-life”
  5. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Groups at risk · read 2026-08-27
    what it says
    “People with malabsorption syndromes and other gastrointestinal disorders, such as cystic fibrosis, celiac disease, ulcerative colitis, and short bowel syndrome, might not absorb vitamin K properly … Vitamin K status can also be low in patients who have undergone bariatric surgery”
  6. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Osteoporosis · read 2026-08-27
    what it says
    “it is unclear whether supplementation with any form of vitamin K reduces the risk of osteoporosis … MK-4 at either 15 mg/day (1 trial) or 45 mg/day (6 trials) … MK-7 supplementation (180 mcg/day for 3 years) improved bone strength”
  7. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Coronary heart disease · read 2026-08-27
    what it says
    “the role of the different forms of vitamin K on arterial calcification and the risk of coronary heart disease is unclear … in the general population and in patients with chronic kidney disease”
  8. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Health risks from excessive vitamin K · read 2026-08-27
    what it says
    “The FNB did not establish ULs for vitamin K because of its low potential for toxicity … no adverse effects associated with vitamin K consumption from food or supplements have been reported in humans or animals”
  9. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Interactions: warfarin · read 2026-08-27
    what it says
    “Vitamin K can have a serious and potentially dangerous interaction with anticoagulants such as warfarin (Coumadin) … maintain a consistent intake of vitamin K … because sudden changes in vitamin K intakes can increase or decrease the anticoagulant effect”
  10. NIH ODS — Vitamin K (Health Professional), updated March 29, 2021 — Interactions: antibiotics, bile acid sequestrants, orlistat · read 2026-08-27
    what it says
    “Antibiotics can destroy vitamin K-producing bacteria in the gut … cholestyramine (Questran) and colestipol (Colestid) … can also reduce the absorption of vitamin K … Combining orlistat with warfarin therapy might cause a significant increase in prothrombin time”
  11. Efficacy of vitamin K2 in the prevention and treatment of postmenopausal osteoporosis: systematic review and meta-analysis of RCTs (Ma et al., Front Public Health 2022) · read 2026-08-27
    what it says
    “Sixteen RCTs with a total of 6,425 subjects … a significant improvement in lumbar spine BMD (BMD LS) (P = 0.006) with VK2 … no significant difference in fracture incidence between the two groups (RR=0.96, P=0.65)”
  12. HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), s4.8 general-adult limits, Table 4 Vitamins Limits + List of Health Claims row 99 · read 2026-08-27
    what it says
    “HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5 … Table 4: Vitamins Limits … Vitamin K1 / K2 0.12mg … Maintain/support bone health … Vitamin D, K”
  13. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. 001 (October 2025), Annex A rows 116–117 · read 2026-08-27
    what it says
    “116. Vitamin K1, Vitamin K2 Restricted use in HS and TM Restricted to oral dosage forms of multi-vitamin/mineral preparations for adults … maximum recommended daily dose should not provide more than 0.12mg … 117. Vitamin K3 (menadione) Prohibited in HS and TM”
  14. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. 001 (October 2025), Annex A row 116 cautionary statement · read 2026-08-27
    what it says
    “Cautionary Statement The following statement should be included: “This product contains vitamin K. Consult a healthcare professional prior to use if you are taking a blood thinner such as warfarin."”
  15. FDA — Daily Value on the Nutrition and Supplement Facts Labels (Reference Guide: Daily Values for Nutrients), content current as of 03/05/2024 · read 2026-08-27
    what it says
    “Vitamin K 120mcg … DVs are the recommended amounts of nutrients to consume or not to exceed each day”
  16. iHerb Singapore — Vitamin K category page (default order), first listings · read 2026-08-27
    what it says
    “1 - 48 of 226 results … California Gold Nutrition, Vitamin D3 + K2 as MK-7 … Futurebiotics, Vitamin K2 + D3 … Sports Research, D3 + K2 … Thorne, Vitamin D + K2 … NOW Foods, MK-7 Vitamin K-2, 100 mcg”
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Updated 2026-08-30. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.