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Vitamin

Vitamin K2 (MK-4)

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Vitamin K2 (MK-4). Short-acting K2 form used at high dose in Japanese osteoporosis protocols.

How it works. Same carboxylation cofactor as MK-7 but shorter half-life; tissue-specific accumulation.

What the research supports. 1 graded claims. Strongest: Reduces vertebral fractures at 45 mg/d (Japanese trials) (moderate).

How much to take. Typical dose: 45 mg/d (Japanese protocol).

Side effects and interactions. 1 medication interaction listed. Serious: Discontinue and seek medical advice if symptoms are severe, persistent, or include difficulty breathing.

Stacking. Pairs well with A high-quality multivitamin, Omega-3 (EPA/DHA).

Common forms. Available as Capsule or softgel, Sublingual tablet or liquid, Methylated active form for sensitive individuals, Multivitamin matrix.

Key studies. 8 studies cited. The strongest are listed with links to PubMed.

Community. Experiences from people who have tried Vitamin K2 (MK-4). Anecdotes are not medical advice.

Vitamin K2 (MK-4). Short-acting K2 form used at high dose in Japanese osteoporosis protocols.

Molecular structureC31H40O2 · 444.6 g/mol

What it is

Short-acting K2 form used at high dose in Japanese osteoporosis protocols.

Food sources

Whole-food sources (animal products for fat-soluble and B-complex vitamins; produce for water-soluble vitamins)Fortified foods (cereals, dairy, plant milks, nutritional yeast)Multivitamins or stand-alone supplements in synthetic or food-derived form

Goals

Bone Health

How it works

Same carboxylation cofactor as MK-7 but shorter half-life; tissue-specific accumulation.

Pathways

  • Same carboxylation cofactor as MK-7 but shorter half-life
  • tissue-specific accumulation

Effects

  • ↓vertebral fractures at 45 mg/d (Japanese trials) decreases

What the research supports

Reduces vertebral fractures at 45 mg/d (Japanese trials)moderate

Strong: consistent results across large trials or meta-analyses. Moderate: several trials, mostly positive. Limited: small or mixed studies. Preclinical: animal or cell research only.

Typical dose
45 mg/d (Japanese protocol)
TimingConsistent daily timing recommended; split larger doses if GI tolerance is a concern.
With foodWith fat
Best formMost evidence is based on the capsule or softgel form.
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Side effects & interactions

Common side effects

  • Vitamin K2 (MK-4) is generally well-tolerated at evidence-based doses
  • Mild GI discomfort (nausea, loose stools, or bloating) possible at higher intakes
  • Headache or transient fatigue reported by a small fraction of users

Serious

  • Discontinue and seek medical advice if symptoms are severe, persistent, or include difficulty breathing

Medication interactions

Warfarinsevere

Antagonizes warfarin.

Check any supplement–medication combination with your pharmacist before starting.

Combines with

Pairs well

  • A high-quality multivitaminCovers micronutrient cofactors that support most supplement pathways.
  • Omega-3 (EPA/DHA)Foundational anti-inflammatory support that complements most regimens.

Common forms

  • Capsule or softgel
  • Sublingual tablet or liquid
  • Methylated active form for sensitive individuals
  • Multivitamin matrix

Key studies

8 studies cited in total.

PubMed: Vitamin K2 (MK-4) — Reduces vertebral fractures at 45 mg/d ↗
Systematic review · PubMed (NLM) · 2026

Opens current human and preclinical literature matching Vitamin K2 (MK-4) and "Reduces vertebral fractures at 45 mg/d". Filter by RCT, meta-analysis, or year on the results page.

PubMed: Vitamin K2 (MK-4) — randomized controlled trial ↗
Systematic review · PubMed (NLM) · 2026

Opens current human and preclinical literature matching Vitamin K2 (MK-4) and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

PubMed: Vitamin K2 (MK-4) — meta-analysis ↗
Systematic review · PubMed (NLM) · 2026

Opens current human and preclinical literature matching Vitamin K2 (MK-4) and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

Discussion

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