Vitamin K2: MK-4 vs MK-7 — Which Form Should You Take?

Vitamin K2 directs calcium into bones and teeth while keeping it out of arteries and soft tissue. But the two supplemental forms—MK-4 and MK-7—differ substantially in their pharmacokinetics, dosing requirements, and tissue distribution. Understanding these differences helps you choose the right form.

Quick answer

MK-7 (from natto) requires lower doses (100-200mcg), stays in the blood for 72+ hours, and is the better choice for cardiovascular protection and long-term bone health. MK-4 requires much higher doses (1,000-45,000mcg), clears the blood in hours, but has unique tissue effects including gene regulation and may specifically benefit bone density at pharmacological doses. Most people should choose MK-7 for daily supplementation.

How vitamin K2 works

Vitamin K2 activates proteins through a process called carboxylation. The two most important proteins it activates:

Osteocalcin: Produced by osteoblasts (bone-building cells). When activated by K2, osteocalcin binds calcium and deposits it into bone matrix. Inactive (uncarboxylated) osteocalcin leaves calcium in the bloodstream.

Matrix GLA protein (MGP): Produced in blood vessel walls. When activated by K2, MGP prevents calcium from depositing in arterial walls. Inactive MGP allows arterial calcification—a major cardiovascular risk factor.

Both MK-4 and MK-7 activate these proteins, but they differ in how long they last in the body and where they concentrate.

MK-7 (menaquinone-7)

Source

Primarily from natto (Japanese fermented soybeans) or produced by bacterial fermentation (Bacillus subtilis). The most common supplemental form worldwide.

Pharmacokinetics

• Half-life: ~72 hours (long)
• Steady-state: Builds up with daily dosing, maintaining consistent blood levels
• Tissue distribution: Circulates in the blood for days, reaching liver, bone, and arterial tissue
• Effective dose: 100-200mcg daily (some studies up to 360mcg)

Advantages

• Low doses work: 100-200mcg is sufficient for most benefits
• Once-daily dosing: Long half-life means one dose per day maintains levels
• Best for arterial protection: Sustained blood levels mean continuous MGP activation in blood vessel walls
• Well-studied for cardiovascular outcomes: The Rotterdam Study and other epidemiological studies showing K2 cardiovascular benefits primarily reflect MK-7 intake (from natto consumption)

Clinical evidence

• Bone density: 180mcg MK-7 daily for 3 years improved bone mineral density and bone strength in postmenopausal women (Knapen et al., 2013)
• Arterial stiffness: 180mcg MK-7 for 3 years improved arterial stiffness measures
• Osteocalcin carboxylation: 100-200mcg consistently reduces uncarboxylated osteocalcin

Considerations

• Can accumulate with daily dosing (long half-life)
• Interacts with warfarin more significantly than MK-4 (because it persists in the blood longer). If on warfarin, consistent dosing is essential and must be coordinated with your doctor.

MK-4 (menaquinone-4)

Source

Can be produced by the body from vitamin K1 (phylloquinone) through a conversion process. Also found in animal-derived foods (egg yolks, butter, liver, cheese—especially from grass-fed animals). Supplemental MK-4 is usually synthetic.

Pharmacokinetics

• Half-life: 1-2 hours (very short)
• Peak blood level: 2-4 hours after ingestion
• Tissue distribution: Rapidly taken up by tissues, particularly brain, pancreas, and reproductive organs
• Effective dose: 1,000-45,000mcg daily (divided doses required due to short half-life)

Advantages

• Unique gene regulation: MK-4 activates SXR/PXR nuclear receptor, regulating genes involved in bone metabolism independently of the standard vitamin K carboxylation pathway. This is unique to MK-4.
• Brain tissue concentration: MK-4 is the predominant form of K2 in the brain. May have neuroprotective effects.
• Pharmacological bone benefits: At 45mg (45,000mcg) daily, MK-4 is approved in Japan for osteoporosis treatment. Multiple Japanese studies show significant fracture reduction.
• Reproductive health: MK-4 concentrates in reproductive tissues and may support fertility.

Clinical evidence

• Osteoporosis (Japan): 45mg/day MK-4 reduced vertebral fractures by 80%, hip fractures by 77%, and non-vertebral fractures by 81% in a large Japanese trial
• Bone quality: Improves bone collagen cross-linking, not just mineral density
• Cancer: Some studies suggest anti-cancer effects, particularly for liver cancer

Considerations

• Must be taken in divided doses (at least 3x daily) due to short half-life
• Therapeutic bone doses (45mg) are expensive
• Less cardiovascular evidence than MK-7
• At standard supplement doses (100-1,000mcg), MK-4 may not maintain sustained blood levels

Head-to-head comparison

| Feature | MK-7 | MK-4 | |---------|------|------| | Half-life | ~72 hours | 1-2 hours | | Effective dose | 100-200mcg | 1,000-45,000mcg | | Dosing frequency | Once daily | 2-3 times daily | | Cardiovascular evidence | Strong | Limited | | Bone evidence | Good | Strong (at 45mg/day) | | Brain concentration | Lower | Higher | | Gene regulation (SXR) | No | Yes | | Warfarin interaction | More significant | Less significant | | Cost per effective dose | Lower | Higher |

Which should you take?

Choose MK-7 if:

• You want cardiovascular protection (arterial calcification prevention)
• You take vitamin D (standard pairing)
• You prefer once-daily dosing
• General health maintenance is the goal
• Budget is a consideration

Choose MK-4 if:

• You have osteoporosis and want pharmacological bone treatment (45mg/day)
• You're specifically targeting brain health
• You're on warfarin and need a form with less sustained interaction
• You have specific concerns about reproductive health

Consider combining both if:

• You want both cardiovascular and bone-specific benefits
• Example protocol: MK-7 100-200mcg daily + MK-4 1,000mcg with each meal

Dosing recommendations

| Goal | Form | Dose | |------|------|------| | Vitamin D pairing | MK-7 | 100-200mcg daily | | Cardiovascular protection | MK-7 | 200-360mcg daily | | Bone health (prevention) | MK-7 | 180-200mcg daily | | Bone health (treatment) | MK-4 | 15mg three times daily (45mg total) | | Brain health | MK-4 | 1,000-5,000mcg daily in divided doses |

Safety and drug interactions

Warfarin users: Vitamin K2 affects warfarin dosing. If you take warfarin, don't start or stop K2 without consulting your doctor. If you do take K2 with warfarin, keep the dose absolutely consistent day-to-day.

No upper limit established: K2 doesn't cause blood clotting beyond normal (unlike the misconception). There's no established upper intake level. Doses up to 45mg MK-4 are used therapeutically without toxicity.

Bottom line

For most people, MK-7 at 100-200mcg daily is the optimal choice—it's effective, affordable, requires once-daily dosing, and has the strongest cardiovascular evidence. MK-4 shines at pharmacological doses for osteoporosis treatment and has unique brain benefits. The ideal approach for comprehensive K2 coverage may be combining both forms: MK-7 for sustained cardiovascular protection and MK-4 for tissue-specific effects.

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