Vitamin K2 (MK-4)

Short-chain vitamin K2 form with rapid action but shorter duration, used in Japanese osteoporosis treatment

Scientific nameMenaquinone-4 FormulaC31H40O2 Molecular weight444.65 g/mol CAS863-61-6

0 absorption score

0 safety / 10

0 USD per month

0 documented interactions

Check it against something

Evidence level A

Vitamin K2 (MK-4) with:

66 out of 100

Needs attention Separate by 2-4 hours to avoid the interaction below.

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What it does

mechanism and evidence for each claim

Rapid bone mineralization

Quickly activates osteocalcin for bone formation

Fast gamma-carboxylation of bone proteins Evidence A-grade 4-8 weeks

Osteoporosis treatment

Proven to reduce fracture risk in clinical trials

Enhanced bone mineral density and quality Evidence A-grade 6-12 months

Quick tissue saturation

Rapidly reaches bone and other tissues

Short-chain structure allows fast distribution Evidence B-grade 2-4 weeks

Cardiovascular support

Activates matrix Gla protein for arterial health

Prevents calcium deposits in arterial walls Evidence B-grade 8-16 weeks

Flexible dosing

Can be dosed multiple times daily for consistent levels

Short half-life allows dose timing optimization Evidence B-grade Immediate

Others people take for the same thing

Same goal, different mechanism — check any of them against this one

Calcium Bone health & muscle function 1,000-1,200 mg A 30% Turmeric Anti-inflammatory & antioxidant 300-1000mg A 3% Vitamin D3 Bone health & immune support 1000-2000 IU A 85% Collagen Peptides Skin health & joint support 5-15g B 85% Calcium Carbonate Affordable bone health & antacid 1000-1200 mg A 25% Phosphorus Bone health & energy metabolism 700-1250mg A 80%

Or a different form of the same thing

the comparison people search most

Vitamin K2 (MK-4) vs Vitamin K2 (MK-7) absorption 60 against 80 · $35 against $25 a month 80% Vitamin K2 (MK-4) vs Vitamin K2 (MK-9) absorption 60 against 85 · $35 against $120 a month 85% Vitamin K2 (MK-4) vs Vitamin K1 (Phylloquinone) absorption 60 against 80 · $35 against $8 a month 80%

All Vitamin K forms ranked by absorption →

Every pair we checked

12 combinations scored by the engine

Dosage

Multiple doses with fat

Daily15-45 mg (divided doses)

Maintenance5-15 mg daily

Therapeutic15-45 mg daily

Osteoporosis protocol45 mg daily (Japanese studies)

Dosing frequency2-3 times daily for optimal levels

Before you take it

VeganYes

When to expect it

First Effects2-4 weeks for protein activation

Peak Benefits6-12 months for bone density improvements

Deficiency DevelopmentWeeks to months with inadequate intake

Toxicity OnsetNo known toxicity at supplemental doses

How to measure it

$100-150

MarkerUndercarboxylated osteocalcin (ucOC)

Optimal<20% of total osteocalcin

FrequencyBaseline and 1-3 months after starting (due to short half-life)

What people actually reported to the FDA

CAERS, 33 reports naming it as the suspect

Most reported effects

Pain 3

Chest pain 3

Death 3

Nephrolithiasis 3

Atrial fibrillation 3

Named as the suspect 33 reports of 92 that mention it at all

Serious outcome 85% hospitalisation, emergency room or worse

Other Serious or Important Medical Event21

Hospitalization17

Visited Emergency Room8

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

What actually reaches you

The label counts the carrier, your body does not

Absorption High 60 of 100 · absorbs well relative to other forms

Delivered daily 18 mg

Cost per 100 mg delivered $6.48 comparative — uses the absorption score, not a measured percentage

Works better with

3 documented

Vitamin D3

D3 increases calcium absorption, K2 directs it to bones

Complementary calcium metabolism pathways · level A

Magnesium

Required for vitamin K-dependent protein function

Cofactor for gamma-carboxylase enzyme · level B

Calcium

K2 optimizes calcium utilization and placement

Activates proteins that bind and direct calcium · level A

What not to take with Vitamin K2 (MK-4)

2 documented

Vitamin A Excess

High doses may interfere with K2 function

Competition for similar metabolic pathways · mild significance

Vitamin E Excess

Very high doses may reduce K absorption

Competition for fat-soluble vitamin absorption · mild significance

Medication interactions

Discuss these with a pharmacist before combining

warfarin-coumadin Major

May reduce anticoagulant effectiveness

What to do: Consult physician, monitor INR closely

antibiotics-broad-spectrum Mild

May reduce vitamin K2 production by gut bacteria

What to do: Consider K2 supplementation during antibiotic use

Available forms

bioavailability compared

Ranks 4 of 4 among vitamin k forms. Vitamin K2 (MK-9) absorbs better — 85%. Compare all forms →

Menaquinone-4 (MK-4) 60

Menaquinone-4 (MK-4): Fast-acting, Proven in osteoporosis, Multiple dosing flexibility, Animal-derived

Food sources

before you supplement

Goose liver 369 mcg/100g · 80

Chicken liver 14 mcg/100g · 75

Egg yolks (pasture-raised) 32 mcg/100g · 70

Butter (grass-fed) 15 mcg/100g · 75

Ground beef 8 mcg/100g · 70

Too little

deficiency signs

Easy bruising and bleeding
Poor bone mineralization
Increased arterial calcification
Dental problems
Increased fracture risk
Subclinical vitamin K deficiency
May manifest as bone loss

Too much

toxicity signs

No known toxicity from natural forms
Potential interaction with blood thinners
Mild digestive upset at very high doses
No upper limit established
Generally well-tolerated even at high doses

Who benefits most

osteoporosis-patients

Proven effective in clinical trials for bone density

15-45 mg daily (divided doses)

rapid-bone-support-needed

Fast-acting form for quick bone protein activation

15-30 mg daily (divided doses)

flexible-dosing-preferred

Short half-life allows customized dosing schedules

5-15 mg 2-3 times daily

japanese-protocol-followers

Want to follow proven Japanese osteoporosis protocols

45 mg daily (divided doses)

animal-product-consumers

Natural form found in animal foods

5-15 mg daily

Where to buy it

compare forms first

Look for Vitamin K2 (MK-4) at 15-45 mg (divided doses) per serving. The form that matters here is Menaquinone-4 (MK-4).

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How it works

Rapid gamma-carboxylation of vitamin K-dependent proteins
Fast activation of osteocalcin for bone mineralization
Quick activation of matrix Gla protein (MGP)
Regulation of calcium deposition in tissues
Short-chain structure allows rapid tissue distribution
Multiple dosing maintains consistent tissue levels

Key findings

what the evidence supports

Reduces bone fractures by 60% in Japanese osteoporosis studies
45mg daily proven effective for postmenopausal bone loss
Shorter half-life but rapid tissue uptake compared to MK-7
Approved osteoporosis treatment in Japan since 1995

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Vitamin K2 (MK-4)?

Documented effects: Rapid bone mineralization; Osteoporosis treatment; Quick tissue saturation; Cardiovascular support. Quickly activates osteocalcin for bone formation

How much Vitamin K2 (MK-4) should you take per day?

The common daily range is 15-45 mg (divided doses). By goal — maintenance: 5-15 mg daily; therapeutic: 15-45 mg daily; osteoporosis protocol: 45 mg daily (Japanese studies); dosing frequency: 2-3 times daily for optimal levels.

When is the best time to take Vitamin K2 (MK-4)?

Multiple doses with fat. First effects are typically reported within 2-4 weeks for protein activation.

What are the side effects of Vitamin K2 (MK-4)?

At excessive doses: No known toxicity from natural forms, Potential interaction with blood thinners, Mild digestive upset at very high doses, No upper limit established, Generally well-tolerated even at high doses. Safety rating at normal doses is 9 out of 10.

What should you not take with Vitamin K2 (MK-4)?

Separate it from Vitamin A Excess, Vitamin E Excess by two to four hours. High doses may interfere with K2 function

Does Vitamin K2 (MK-4) interact with medications?

Documented interactions with warfarin-coumadin, antibiotics-broad-spectrum. Discuss these with a pharmacist before combining.

How do you know if you need Vitamin K2 (MK-4)?

The marker is Undercarboxylated osteocalcin (ucOC), optimal range <20% of total osteocalcin. Common deficiency signs: Easy bruising and bleeding, Poor bone mineralization, Increased arterial calcification, Dental problems.

Taken for

38 Joints & Bones

Vitamin D3 · Calcium Carbonate · Bovine Collagen