Vitamin K
Research reviewed: Up until 03/2026
Vitamin K is a dietary supplement with 6 published peer-reviewed studies involving 487 participants, researched for Blood Coagulation, Bone Health.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Blood Coagulation
ModerateBone Health
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Blood Coagulation
To determine the effects of low-dose vitamin K2 supplements, at doses as small as 10 µg/day, on the blood-thinning effect of oral anticoagulants (specifically acenocoumarol, a vitamin K antagonist/VKA, which is a class of drugs that deliberately block vitamin K's clotting activity to prevent dangerous blood clots).
Study Type
Randomised, placebo-controlled, dose-escalation intervention study
Purpose
To determine the effects of low-dose vitamin K2 supplements, at doses as small as 10 µg/day, on the blood-thinning effect of oral anticoagulants (specifically acenocoumarol, a vitamin K antagonist/VKA, which is a class of drugs that deliberately block vitamin K's clotting activity to prevent dangerous blood clots).
Dose
Three escalating doses of vitamin K2 (as MK-7): 10 µg/day → 20 µg/day → 45 µg/day, each given for 6-day intervals while participants continued their established acenocoumarol dose
Participants
18 healthy men and women (15 reached received full vitamin K doses), aged 18–45 years
Duration
Participants first had 4 weeks on acenocoumarol (a blood thinner) to stabilize their condition, followed by 6 weeks of gradually increasing doses of MK-7
Results
Researchers observed significant effects of MK-7 (vitamin K2) on blood clotting. At 45 µg/day, it significantly lowered INR (International Normalized Ratio - a measure of how quickly blood clots, lower means faster clotting) and reduced uncarboxylated Factor II (an inactive form of a key clotting protein; lower levels mean more active clotting protein) by about 40%. Even at lower doses (10–20 µg/day), 40–60% of participants showed drops in INR, while endogenous thrombin potential (ETP) (the blood’s overall ability to form clots) increased by about 20–30%. Overall, this means even small amounts of vitamin K2 can significantly make blood clot faster and reduce the effect of blood thinners.
To investigate the effects vitamin K2 (menaquinones) affect the activation of certain proteins that help regulate calcium and support bone health and to determine whether MK-7 at nutritional doses has any effect on thrombin generation (the core process of blood clot formation).
Study Type
Randomised, double-blind, placebo-controlled dose-response trial
Purpose
To investigate the effects vitamin K2 (menaquinones) affect the activation of certain proteins that help regulate calcium and support bone health and to determine whether MK-7 at nutritional doses has any effect on thrombin generation (the core process of blood clot formation).
Dose
Placebo, or 10 / 20 / 45 / 90 / 180 / 360 µg/day of vitamin K2 (as MK-7)
Participants
42 healthy Dutch men and women aged 18–45 years
Duration
12 weeks
Results
No adverse effects on thrombin generation (neither endogenous thrombin potential nor peak thrombin concentration) were observed at any dose, confirming that MK-7 supplementation at nutritional doses does not activate the blood clotting system in healthy individuals with normal vitamin K status.
Bone Health
To investigate the effect of vitamin K2 supplementation on bone mineral density (measures the amount of calcium and minerals in a specific volume of bone, indicating strength and fracture risk) in patients on chronic kidney dialysis, who suffer from accelerated bone loss as a complication of kidney failure.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effect of vitamin K2 supplementation on bone mineral density (measures the amount of calcium and minerals in a specific volume of bone, indicating strength and fracture risk) in patients on chronic kidney dialysis, who suffer from accelerated bone loss as a complication of kidney failure.
Dose
360 µg/day vitamin K2 (as MK-7) or placebo
Participants
123 male and female patients on chronic dialysis treatment with an average age of 65 years
Duration
2 years
Results
Dialysis patients normally lose bone density quickly as a complication of kidney failure. After 2 years of vitamin K2 supplementation, the study found an association between vitamin K2 and significant prevention of the decline in lumbar spine bone mineral density (the lower back region of the spine, one of the most fracture-prone areas in kidney failure patients). On the other hand, bone mineral density of the lumbar spine decreased significantly in the placebo group. dp-ucMGP (the inactive form of a protein in the blood that helps prevent calcium buildup in blood vessels) was also significantly decreased by vitamin K2, suggesting it may help activate protective proteins that prevent harmful calcium buildup in blood vessels.
To directly compare the efficacy of MK-7 (vitamin K2) versus phytomenadione (vitamin K1) on Matrix Gla Protein activation — the key protein that protects against vascular calcification and also has roles in bone metabolism — in hemodialysis patients, where severe vitamin K deficiency drives both vascular and skeletal complications.
Study Type
Prospective, randomised controlled trial
Purpose
To directly compare the efficacy of MK-7 (vitamin K2) versus phytomenadione (vitamin K1) on Matrix Gla Protein activation — the key protein that protects against vascular calcification and also has roles in bone metabolism — in hemodialysis patients, where severe vitamin K deficiency drives both vascular and skeletal complications.
Dose
Group 1: 90 µg/day vitamin K2 (MK-7); Group 2: 10 mg vitamin K1 (phytomenadione) three times weekly; Group 3: placebo
Participants
120 hemodialysis patients (40 per group)
Duration
3 months
Results
Researchers observed that MGP levels (a protein that helps prevent calcium buildup in blood vessels) increased significantly in the vitamin K2 group after 3 months, more than in the vitamin K1 or placebo groups. The vitamin K2 group showed the largest improvement, with MGP levels rising by about 700%, compared to 78% in the vitamin K1 group and 40% in the placebo group. This suggests that vitamin K2 is much more effective at activating this protective protein.
To investigate the investigate the effects of vitamin K2 as an add-on to calcium and vitamin D supplementation on osteocalcin (a protein involved in bone formation), bone mass (the amount of bone tissue in the body), and microarchitecture (the internal structure and quality of bone) in postmenopausal women.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the investigate the effects of vitamin K2 as an add-on to calcium and vitamin D supplementation on osteocalcin (a protein involved in bone formation), bone mass (the amount of bone tissue in the body), and microarchitecture (the internal structure and quality of bone) in postmenopausal women.
Dose
375 µg/day vitamin K2 (as MK-7) or placebo
Participants
142 postmenopausal women with osteopenia
Duration
3 years
Results
After 1 year, the researchers observed that undercarboxylated osteocalcin levels (a bone protein linked to poorer bone quality) dropped significantly in the vitamin K2 group by −65.2% compared to almost no change in the placebo group −0.03%. However, after 3 years, bone mineral density (aBMD) (a measure of bone strength) and one turnover marker (indicators of how fast bone is broken down and rebuilt) showed no significant difference between groups. Overall, earlier results showed early benefits in bone protein after 1 year with vitamin K2.
To investigate the effects vitamin K2 (menaquinones) affect the activation of certain proteins that help regulate calcium and support bone health and to determine whether MK-7 at nutritional doses has any effect on thrombin generation (the core process of blood clot formation).
Study Type
Randomised, double-blind, placebo-controlled dose-response trial
Purpose
To investigate the effects vitamin K2 (menaquinones) affect the activation of certain proteins that help regulate calcium and support bone health and to determine whether MK-7 at nutritional doses has any effect on thrombin generation (the core process of blood clot formation).
Dose
Placebo, or 10 / 20 / 45 / 90 / 180 / 360 µg/day of vitamin K2 (as MK-7)
Participants
42 healthy Dutch men and women aged 18–45 years
Duration
12 weeks
Results
High-dose of vitamin K2 (doses around the EU RDA of 75 µg/day) significantly improved activation of vitamin K-dependent proteins: ucOC (undercarboxylated osteocalcin - the inactive bone-building protein that cannot bind calcium without vitamin K; high ucOC indicates vitamin K deficiency in bone tissue) decreased significantly, and dp-ucMGP (inactive form of the vascular calcification-inhibiting protein; elevated levels indicate the arteries are poorly protected) decreased significantly compared to placebo.
Frequently Asked Questions
Common questions about Vitamin K research
There are currently 6 peer-reviewed studies on Vitamin K (Vitamin K), involving 487 total participants. Research covers Blood Coagulation, Bone Health. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (6 human studies), and reported outcomes.
Vitamin K has been researched for: Blood Coagulation, Bone Health. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 6 out of 6 studies are human trials. Human trials carry more weight in our evidence scoring system.
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