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Vitamin K

Vitamin K

Best for

Lower fracture risk

Proven benefit 104–208 weeks 4 meta-analyses, n=10.3k #1 of 5 studied

Vitamin K provides a proven benefit for fragility-fracture risk, while bone-density gains are modest and artery benefits remain unproven overall.

Median effective dose, most-studied outcomes

  • Maintain bone density 45 mg 78–156 wk
  • Lower fracture risk 45 mg 104–208 wk
  • Protect your spinal bones 360 mcg 26–156 wk
Full protocol, 9 outcomes

Risk, worst reported severity

  • Anaphylactic reaction severe
  • Hemolytic anemia severe
  • warfarin major
  • orlistat moderate
All 14 events and interactions

What vitamin k actually does

Outcome Effect Evidence Dose Time Rank
Clear benefits 1
Lower fracture risk Proven benefit Fractures can limit mobility and independence, especially after a fall.
moderate 		4 meta-analyses 5 papers · n=10k — 104–208 wk #1 /5
Modest benefits 3
Build bone density Proven modest benefit Bone density reflects the mineral that helps bones bear weight and resist breaking.
small 		4 meta-analyses 10 papers · n=7.0k — 26–156 wk #2 /14
Build stronger bones Likely modest benefit A bone's strength and shape help it handle force without breaking.
small 		2 RCTs 2 papers · n=313 1–45 mg 78–156 wk —
Balance bone turnover Proven but unnoticeable Bone turnover replaces old bone with new bone to maintain the skeleton over time.
trivial 		3 meta-analyses 11 papers · n=7.0k — 1–156 wk #1 /11
Early research 1
Slower artery hardening with atherosclerosis Not enough research Atherosclerosis is plaque buildup in arteries that can restrict blood flow.
trivial 		1 meta-analysis 8 papers · n=942 — 26–104 wk #1 /6

Effect tiers come from native-unit MCID where available, Cohen's d otherwise.

Protocol

Dose, timing & forms

How much

The strongest fracture evidence comes from long-term trials of 45 mg/day of MK-4, often followed for roughly two to four years. 12 Bone-density findings are smaller and come from both high-dose MK-4 protocols and much lower-dose MK-7 protocols, so a label's dose alone does not tell you whether it matches the fracture research. 23 Do not treat the high MK-4 research dose as a general nutrition target, especially if you use anticoagulant medication.

When and how long

Bone research uses vitamin K every day for long stretches, because bone remodeling moves slowly. 13 Take supplemental vitamin K with a meal that contains some fat, since it is fat-soluble. The trials do not establish a meaningful advantage for morning versus evening dosing, so consistency matters more than clock time. 3

Forms & standardisation

For fracture outcomes, the most recognizable research protocol uses menaquinone-4, also called menatetrenone or MK-4. 12 Lower-dose, long-term bone-density research often uses menaquinone-7, or MK-7. 3 Check the label for the exact form and amount, rather than assuming every product labeled “K2” matches the same evidence.

Studied range, by outcome

Outcome Studied range Median effective Duration Evidence
Maintain bone density — 45 mg 78–156 wk 9 papers 1 sig. endpoint
Slow calcium buildup in arteries — — 26–104 wk 7 papers
Lower fracture risk 5–45 mg 45 mg 104–208 wk 5 papers 12 sig. endpoints
Protect your spinal bones 360–500 mcg 360 mcg 26–156 wk 5 papers 1 sig. endpoint
Slow excessive bone resorption — — 78 wk 2 papers
Build bone mineral stores 45 mg 45 mg 12–156 wk 2 papers 1 sig. endpoint
Support stronger bones under load 1–45 mg 45 mg 78–156 wk 2 papers 7 sig. endpoints
Protect forearm bones 360 mcg — 104 wk 2 papers
Reduce forearm fracture risk 45 mg — — 1 paper

Adverse events and drug interactions

Safety events

Anaphylactic reaction severe
Hemolytic anemia severe
Hypoprothrombinemia severe
Hemorrhage severe
Pulmonary embolism severe
Deep vein thrombosis severe
nausea mild
irritability mild

Drug interactions

warfarin major decreases effect
orlistat moderate decreases concentration
rifampicin moderate decreases concentration
asciminib moderate additive
ponatinib moderate additive
antineoplastic agents moderate unknown
Buy well

Recommended Vitamin K products

Real products that dose Vitamin K where the research does, in a clean formulation, from brands we've audited. We only list ones we'd stand behind.

Chosen for adequate Vitamin K dosing vs. the studied range, a clean formulation (grade A–C), and independent brand-quality audits. Not sponsored.

In context

What this is and how it works

  • Across 5 studies (n=10,290), vitamin K lowered fragility-fracture risk across 29 endpoints. 1
  • The review covered 43 papers and 73 outcomes spanning fracture, bone-density, and cardiovascular measures.
  • Evidence includes menaquinone forms in postmenopausal women, limiting generalization across supplements and populations.

Vitamin K is a family of fat-soluble nutrients. Vitamin K1 comes mostly from leafy green plants, while vitamin K2 includes menaquinones such as MK-4 and MK-7, which appear in some animal and fermented foods and in supplements. 23

Vitamin K switches on proteins through a chemical finishing step called carboxylation. Think of it as adding the snap fasteners that let bone proteins grab calcium and secure it into the skeleton. 3 It also activates matrix Gla protein, a protein involved in handling calcium in blood-vessel tissue, though trials have not established a meaningful artery-hardening benefit. 4

Bottom line

Vitamin K is most compelling for people focused on long-term bone health, particularly when fracture prevention matters more than chasing a fast, visible change. The fracture signal is meaningful, while bone-density gains are modest and artery claims remain unproven. 124 Skip self-directed supplementation if you take warfarin or another medication that affects clotting, unless your prescribing clinician guides the plan.

Frequently asked

Common questions

Does vitamin K actually reduce fracture risk?

Vitamin K demonstrates a moderate reduction in fragility-fracture risk in reviewed trials, with much of that evidence coming from long-term high-dose menaquinone-4 research. Bone-density changes are smaller, so think of it as a long game for bone maintenance, not a quick rebuild. 12

What is the difference between vitamin K1 and K2?

Vitamin K1, or phylloquinone, is common in leafy greens and is central to normal blood clotting. Vitamin K2 describes menaquinones such as MK-4 and MK-7, the forms most often tested in the bone trials discussed here. 23

How long does vitamin K take to support bones?

Bone trials run for months to years, not days. The fracture studies generally tracked participants for about two to four years, while a three-year MK-7 trial measured bone outcomes over time. 13

Can you take vitamin K with warfarin?

Do not start, stop, or substantially change vitamin K intake without the clinician managing your warfarin. Vitamin K directly changes the clotting system that warfarin is designed to regulate.

Sources

Sources

  1. 1. Vitamin K and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials (2006) ↑
  2. 2. Effect of menatetrenone on bone mineral density and incidence of fractures in postmenopausal women: a systematic review and meta-analysis (2009) ↑
  3. 3. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women (2013) ↑
  4. 4. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women (2015) ↑

Generated August 27, 2026

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