Vitamin K
Vitamin K is an essential vitamin — a fat-soluble vitamin family including K1 (phylloquinone) and K2 (menaquinones). 32 peer-reviewed studies are available in our database. Common forms include K1 (Phylloquinone), K2 MK-4, K2 MK-7.
Content reviewed by ZYNAVA Research Team · Last updated February 2026 · Editorial policy
Find Quality Vitamin K Supplements
Explore vitamin k supplements and browse options based on ingredient research.
What Is Vitamin K?
A fat-soluble vitamin family including K1 (phylloquinone) and K2 (menaquinones).
Key fact: MK-7 is a K2 form with a longer half-life than MK-4.
Vitamin K Supplement Forms
Vitamin K is available in several supplemental forms: K1 (Phylloquinone), K2 MK-4, K2 MK-7. MK-7 is a K2 form with a longer half-life than MK-4.
Explore Vitamin K Supplements
Use our research tool to explore vitamin k supplements and see what studies have examined.
Research Studies on Vitamin K
Our database contains 32 peer-reviewed studies examining vitamin k. Below are selected recent studies:
Related Supplements
Natural Food Sources of Vitamin K
Vitamin K can be obtained from a variety of whole foods. A food-first approach is generally recommended by nutrition experts, with supplementation considered when dietary intake is insufficient or when specific circumstances increase requirements.
- Kale — One cup of raw kale provides over 500% of the daily value of vitamin K1
- Spinach — One cup of raw spinach provides about 150% of the daily value
- Broccoli — A cup of cooked broccoli provides over 200% of the daily value
- Brussels sprouts — A half cup provides about 140% of the daily value
- Natto — A traditional Japanese food that is one of the richest sources of vitamin K2 (menaquinone-7)
Dietary Context
Vitamin K exists in two main forms: K1 (phylloquinone), found abundantly in green leafy vegetables, and K2 (menaquinone), found in fermented foods and some animal products. K1 is the predominant dietary form, while K2 is increasingly studied for its role in calcium metabolism and cardiovascular health.
Absorption: Food vs. Supplements
Like other fat-soluble vitamins, vitamin K is better absorbed with dietary fat. Interestingly, cooking leafy greens can make vitamin K more bioavailable by breaking down plant cell walls, unlike many water-soluble vitamins that are lost during cooking.
Practical Tips
- People on blood-thinning medications (warfarin) should maintain consistent vitamin K intake rather than avoiding it
- Dark leafy greens are the most reliable source of K1
- Fermented foods like natto and certain cheeses provide K2
How to Take Vitamin K
Proper timing and administration of vitamin k can make a meaningful difference in how well your body absorbs and utilizes it. Here are evidence-based guidelines for optimizing your supplementation routine.
Best time to take: With a meal containing fat
With or Without Food
Vitamin K is fat-soluble and requires dietary fat for proper absorption. Taking with a fat-containing meal significantly improves uptake.
How Often
Once daily. MK-7 (a K2 form) has a longer half-life than K1, allowing for once-daily dosing with sustained activity.
Practical Tips
- MK-7 (from natto or supplements) has the longest half-life and most stable blood levels
- Often paired with vitamin D3 for bone and cardiovascular health
- Green leafy vegetables are the best dietary source of K1
Important Interactions
- Critical interaction with warfarin — vitamin K directly counteracts warfarin's mechanism. Consult your doctor before any K supplementation
- Consistent vitamin K intake (not supplementation changes) is key for warfarin users
- Antibiotics that disrupt gut bacteria may reduce vitamin K2 production
This is not an exhaustive list of interactions. Always consult a healthcare provider or pharmacist about potential interactions with your specific medications and health conditions.
Where to Find Vitamin K Supplements
Vitamin K supplements are widely available from reputable online retailers. When shopping, look for products with third-party testing certifications and transparent ingredient labels to ensure quality.
How to Choose a Quality Vitamin K Supplement
- Verify the expiration date and that the product is stored appropriately
- Research the brand — established companies with transparent testing are generally more reliable
- Consider subscription options for supplements you plan to take long-term — many retailers offer discounts
- Check the other ingredients list for potential allergens (soy, gluten, dairy, nuts)
To explore supplements by ingredient or health goal, try our AI Supplement Advisor.
Research Highlights: Vitamin K
Our database includes 3 meta-analysiss, 2 clinical trials, 1 review examining vitamin k, published between 2024 to 2025. Below are selected findings that illustrate the current state of research. These summaries are educational — not clinical recommendations — and individual outcomes may vary.
The Role of Vitamin K Deficiency in Chronic Kidney Disease-A Scoping Review
Published in Nutrients. Study from 2025.
Source: View full study on PubMed
The effect of vitamin K2 supplementation on bone turnover biochemical markers in postmenopausal osteoporosis patients: a systematic review and meta-analysis
Published in Front Endocrinol (Lausanne). Study from 2025. Comprehensive analysis combining multiple studies.
Source: View full study on PubMed
Effect of Menaquinone-7 (MK-7) Supplementation on Anthropometric Measurements, Glycemic Indices, and Lipid Profiles: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Published in Prostaglandins Other Lipid Mediat. Study from 2025. Comprehensive analysis combining multiple studies.
Source: View full study on PubMed
The effect of vitamin K supplementation on cardiovascular risk factors: a systematic review and meta-analysis
Published in J Nutr Sci. Study from 2024. Comprehensive analysis combining multiple studies.
Source: View full study on PubMed
Vitamin K for Vascular Calcification in Kidney Patients: Still Alive and Kicking, but Still a Lot to Learn
Published in Nutrients. Study from 2024.
Source: View full study on PubMed
Vitamin K2 in Health and Disease: A Clinical Perspective
Published in Foods. Study from 2024.
Source: View full study on PubMed
The research summaries above are based on published peer-reviewed studies and are provided for informational purposes only. Study findings may not apply to all individuals, and the presence of a study summary does not constitute an endorsement of vitamin k for any specific health condition. Always consult a qualified healthcare professional before making decisions based on research findings.
Important Information
Zynava Does Not Sell Supplements
Zynava is an independent supplement search and price-comparison engine. We do not manufacture, sell, or distribute any dietary supplements, vitamins, minerals, or health products. Our role is strictly informational — we show matching supplement options and prices from multiple retailers, and link to published research so you can explore the science yourself. When you click a link to a retailer on our site, you are leaving Zynava and purchasing directly from that third-party retailer. We have no control over their inventory, pricing, shipping, or product quality.
Because we do not sell products, ranking within our search results is never paid — results are ordered by relevance, price, value, rating, and availability, not by profit margins or inventory considerations. This independence is central to our mission.
Our Commitment to Editorial Independence
Zynava maintains strict editorial independence from supplement manufacturers, retailers, and advertisers. The studies we link to are peer-reviewed publications indexed in databases such as PubMed, PMC, and NIH resources. We do not accept payment from supplement brands to feature, promote, or favorably review their products, and ranking within search results is never paid.
Every supplement page on Zynava is generated using the same process regardless of brand or commercial relationship. We do not cherry-pick studies to support a predetermined conclusion — we link to the published research that exists and let you read it for yourself. Zynava does not evaluate or grade the quality of individual studies.
Vitamin K — Quick Reference Summary
This reference summary is provided for quick access to key data about vitamin k. For detailed information, research citations, and context, refer to the full sections above.
- Supplement Name
- Vitamin K
- Category
- essential vitamin
- Overview
- A fat-soluble vitamin family including K1 (phylloquinone) and K2 (menaquinones).
- Studies in Database
- 32 peer-reviewed studies
- Available Forms
- K1 (Phylloquinone), K2 MK-4, K2 MK-7
- Data Sources
- PubMed, PubMed Central (PMC), National Institutes of Health (NIH), peer-reviewed journals
- Content Reviewed
- February 2026
This summary is for informational and educational purposes only. It is not medical advice. Consult a healthcare professional before using any supplement. See our full disclaimer and editorial policy for more information.
This content is for general educational purposes only and is not intended as medical advice. Consult a healthcare professional before starting any supplement. Individual results may vary. See our full disclaimer and affiliate disclosure.