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Vitamin K1

Supplement vitamin heart & metabolicbone & joint
Aka: phylloquinone, phytonadione
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 k1.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
Vitamin K — k1 is the main dietary form, from greens
When to take
With a meal — fat improves phylloquinone absorption
Take with
Food containing some fat
Pros & cons
Pros
  • The main dietary form of vitamin K
  • No upper limit set — low potential for toxicity
  • Free-form absorption is about 80%
Cons
  • Serious interaction with warfarin and similar drugs
  • SG caps supplements at 0.12 mg vitamin K a day
  • Bone and heart findings quoted here are for k2 forms
Sources
  1. NIH ODS — Vitamin K (Health Professional), Introduction · read 2026-08-27
    what it says
    “These compounds include phylloquinone (vitamin K1) and a series of menaquinones (vitamin K2). … Phylloquinone is present primarily in green leafy vegetables and is the main dietary form of vitamin K”
  2. NIH ODS — Vitamin K (Health Professional), Introduction (absorption) · read 2026-08-27
    what it says
    “The absorption rate of phylloquinone in its free form is approximately 80%, but its absorption rate from foods is significantly lower. … Consuming vegetables at the same time as some fat improves phylloquinone absorption”
  3. NIH ODS — Vitamin K (Health Professional), Table 1 Adequate Intakes · read 2026-08-27
    what it says
    “19+ years | 120 mcg | 90 mcg”
  4. NIH ODS — Vitamin K (Health Professional), Sources of Vitamin K (Daily Value) · read 2026-08-27
    what it says
    “The DV for vitamin K is 120 mcg for adults and children age 4 years and older”
  5. NIH ODS — Vitamin K (Health Professional), 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'”
  6. NIH ODS — Vitamin K (Health Professional), Interactions with Medications (warfarin) · read 2026-08-27
    what it says
    “Vitamin K can have a serious and potentially dangerous interaction with anticoagulants such as warfarin (Coumadin) … sudden changes in vitamin K intakes can increase or decrease the anticoagulant effect”
  7. NIH ODS — Vitamin K (Health Professional), Osteoporosis · read 2026-08-27
    what it says
    “Some, but not all, studies also link higher vitamin K intakes with higher bone mineral density and/or lower hip fracture incidence. … MK-4 supplementation significantly reduced rates of hip fractures, vertebral fractures, and all nonvertebral fractures”
  8. NIH ODS — Vitamin K (Health Professional), Coronary heart disease · read 2026-08-27
    what it says
    “Participants in this study who had dietary menaquinone intakes in the mid tertile (21.6–32.7 mcg/day) and upper tertile (>32.7 mcg/day) also had a 27% and 57% lower risk of coronary heart disease mortality”
  9. NIH ODS — Vitamin K (Health Professional), Groups at Risk of Vitamin K Inadequacy · read 2026-08-27
    what it says
    “People with malabsorption disorders (cystic fibrosis, celiac disease, ulcerative colitis, short bowel syndrome) … Patients who have undergone bariatric surgery”
  10. NIH ODS — Vitamin K (Health Professional), Dietary supplements · read 2026-08-27
    what it says
    “Several forms of vitamin K are used in dietary supplements, including vitamin K1 as phylloquinone or phytonadione (a synthetic form of vitamin K1) and vitamin K2 as MK-4 or MK-7”
  11. HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. 020 (January 2026), clause 4.8 and Table 4 Vitamins Limits · 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. … Vitamin K1 / K2 0.12mg”
  12. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in HS and TM (Oct 2025), Annex B row 116 (restriction and maximum daily dose) · 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 … should not provide more than 0.12mg”
  13. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in HS and TM (Oct 2025), Annex B row 116 cautionary statement · read 2026-08-27
    what it says
    “Cautionary Statement … 'This product contains vitamin K. Consult a healthcare professional prior to use if you are taking a blood thinner such as warfarin.'”
  14. iHerb Singapore — 'Vitamin K' category page, default order, 226 results · read 2026-08-27
    what it says
    “Vitamin K … 1 - 48 of 226 results … California Gold Nutrition … Futurebiotics … Sports Research … Thorne … NOW Foods”
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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.