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📰Read the full Vitamin K2 (MK-7) evidence review on GMJ News →Complete clinical article, references and updates on news.gmj.ge. This page is the structured safety summary.⚠ Warfarin patient — MK-7 affects INR. Maintain CONSISTENT intake; adjust warfarin dose [1]
⚠ D3 + K2 + Calcium = bone health foundation [2]
⚠ Rotterdam study: high K2 = 50% lower CV mortality (observational) [2]
⚠ MK-7 (100–200 µg/day) is more practical than MK-4 (45 mg TID) [1]
⚠ Natto is the only food providing therapeutic K2 amounts [1]
ℹ️ Not obtained from food. Obtained mainly from fermented foods (natto) and animal products; total vitamin-K intake is tracked under Vitamin K rather than as a separate MK-7 target.
🔬 Lab interpreter
Recommended test
INR (if on warfarin)
INR (if on warfarin)
Reference range / target
Therapeutic range
Therapeutic range
MK-7's 3-day half-life creates more sustained INR effect than K1 [1].
Full lab monitoring ↓⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
MK-7 is the practical K2 form — 3-day half-life allows once-daily dosing at 100–200 µg. It directs calcium to bone (osteocalcin) and away from arteries (MGP) — the 'calcium paradox' solution. Rotterdam study: 50% lower CV mortality with high K2 intake. The D3-K2-Ca triad is the bone health foundation. Warfarin users: CONSISTENT intake, not avoidance. Natto is 10–20× richer than any other K2 food [1] [2].
1 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: See guidance
Vitamin K important for coagulation. MK-7 not specifically studied in pregnancy [1].
👦 Pediatric: See guidance
Vitamin K1 injection at birth is standard. MK-7 supplementation in children: no specific data [1].
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Standard dose
How to take
🍽 Timing: With fat-containing meal (fat-soluble) [1].
💊 With food: Always with fat [1].
🚫 Avoid: Inconsistent dosing with warfarin [1].
2 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['MK-7 (menaquinone-7)', 'preferred', 'Long half-life (3 days). Once daily. From natto or synthetic. Most studied K2 form [1].'] | Standard | Check label | |
| ['MK-4 (menaquinone-4)', '', 'Short half-life (~1 hour). Requires multiple daily doses (45 mg/day in Japanese osteoporosis studies). Different pharmacokinetics [1].'] | Standard | Check label | |
| ['Vitamin K1 (phylloquinone)', '', 'Primarily hepatic (coagulation). Does NOT significantly carboxylate extrahepatic proteins [1].'] | Standard | Check label |
3 Common questions
K1 vs K2 — what's the difference? ▼
K1 (phylloquinone): primarily hepatic coagulation. Found in leafy greens. K2 (menaquinone): activates extrahepatic proteins (osteocalcin for bone, MGP for arteries). Found in fermented foods and animal products. Both affect coagulation/warfarin [1].
MK-7 vs MK-4? ▼
MK-7: long half-life (3 days), once daily, lower dose (100–200 µg). MK-4: short half-life (~1 hour), needs multiple daily doses at high levels (45 mg — Japanese osteoporosis dose). MK-7 is more practical and most studied outside Japan [1].
Should I take K2 with vitamin D? ▼
Yes — the D3-K2 combination is widely recommended. Vitamin D increases calcium absorption; K2 directs that calcium to bone (via osteocalcin) rather than arteries (via MGP). The triad D3 + K2 + calcium is the foundation of bone health supplementation [2].
Will K2 interfere with warfarin? ▼
YES — MK-7 (like all vitamin K) will reduce INR. However, if intake is CONSISTENT, warfarin dose can be adjusted accordingly. The key is consistency, not avoidance [1].
4 Clinical evidence
Strong
MK-7 carboxylates osteocalcin and MGP — confirmed in dose-response studies [1]. Longer half-life than K1 or MK-4 — confirmed pharmacokinetics [1]. HIGH
Moderate
Bone health: 3-year RCT (n=244 postmenopausal women) showed MK-7 180 µg/day improved bone strength (femoral neck) and reduced vertebral height loss [2]. Vascular calcification: MK-7 reduced vascular stiffness in healthy postmenopausal women (RCT) [2]. Rotterdam study (n=4,807): highest K2 intake tertile had 50% lower cardiovascular mortality and 25% lower all-cause mortality [2]. MODERATE
Insufficient
5 Safety, toxicity & adverse events
Absolute contraindications
✕ Concurrent warfarin or other vitamin-K-antagonist anticoagulants — antagonises the drug's effect
Relative
⚠ If on a vitamin-K antagonist for another reason — keep intake consistent and coordinate with the prescriber
🚩 Red flags
● Warfarin patient with variable K2 intake — INR fluctuations [1]
● Patient taking calcium + D3 WITHOUT K2 — calcium may deposit in arteries rather than bone [2]
6 Interactions
Drug interactions
Warfarin Major
Mechanism: MK-7 activates vitamin K-dependent clotting factors (II, VII, IX, X). 3-day half-life provides sustained INR effect. [1]
Effect: Reduced INR. Thrombotic risk if warfarin dose not adjusted. [1]
Action: Maintain CONSISTENT daily intake. Monitor INR. Adjust warfarin dose. Do NOT intermittently supplement K2 [1].
Supplement synergies
Vitamin D3 · 1,000–2,000 IU D3
D3 increases calcium absorption; K2 directs calcium to bone. The foundational combination [2].
D3 increases calcium absorption; K2 directs calcium to bone. The foundational combination [2].
Calcium · 500–1,000 mg calcium
The D3-K2-Ca triad for bone health [2].
The D3-K2-Ca triad for bone health [2].
Magnesium · 320–420 mg magnesium
Supports both calcium and vitamin D metabolism [2].
Supports both calcium and vitamin D metabolism [2].
7 Regulatory
United States (FDA): Dietary supplement. No health claims [1].
Japan: MK-4 at 45 mg/day is an approved osteoporosis drug (Glakay) [1].
European Union (EFSA): Authorized health claims for vitamin K: blood coagulation and bone maintenance [1].
8 Cite this page
Vancouver: Pkhakadze G. Vitamin K2 (MK-7) — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Aug 15]. Available from: https://supplement.ge/ingredients/vitamin-k2-mk-7/
APA 7th: Pkhakadze, G. (2026). Vitamin K2 (MK-7) — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/vitamin-k2-mk-7/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: February 2027
References: 2 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Vitamin K2 (MK-7) — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/vitamin-k2-mk-7/ CC BY 4.0.
GP
Prof. G. Pkhakadze, MD, MPH, PhD
Professor of Public Health · Head of Department, DTMU
Editor-in-Chief, Georgian Medical Journal (ISSN 3088-4322)
Chair, Public Health Institute of Georgia · UEMS Public Health Section
Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG