Vitamin K2 MK-4 vs. MK-7: What's the Difference?

Both are K2, but they behave very differently in the body. Here's how to pick the right one.

Vitamin K2 sounds like a single nutrient. It's actually a family, and the two forms you'll see on labels, MK-4 and MK-7, behave very differently. Picking the wrong one wastes money.

Why K2 matters

K2 activates the proteins that route calcium into bones and teeth, and out of arteries and soft tissue. Without enough K2, supplemental calcium can ironically accumulate in your arteries instead of strengthening your skeleton. K2 is especially important if you take vitamin D3 (which raises calcium absorption).

MK-4: the short-acting form

• Half-life: ~1 hour
• Typical dose: 1,500 mcg (1.5 mg), 3× daily
• Cost: higher per effective dose
• Where studied: mostly Japan, mostly bone density at very high doses

MK-4 has good evidence, but the half-life is so short that you need multiple daily doses at gram-level amounts. For most consumers, this is impractical.

MK-7: the long-acting form

• Half-life: 3 days
• Typical dose: 90-180 mcg once daily
• Cost: lower per effective dose
• Where studied: growing European literature, arterial elasticity, bone density

MK-7 is naturally produced via fermentation (notably in Japanese natto). The long half-life means once-a-day dosing reaches and stays at effective serum levels.

Which to pick

For 95% of people: MK-7 at 90-180 mcg daily. It's more practical, often cheaper, and has growing modern evidence.

Consider MK-4 only if:

• You're working with a clinician on a specific protocol
• You have severe osteoporosis being treated with high-dose K2 (the Japanese protocols use 45 mg/day)

Combining with D3

Vitamin D3 and K2 work synergistically, D3 increases calcium absorption, K2 directs that calcium correctly. The combination at 2,000-5,000 IU D3 + 90-180 mcg MK-7 is the most-recommended foundational pair.

Food sources

• Natto (fermented soybeans), the richest natural source of MK-7
• Hard cheeses (gouda, brie), modest amounts
• Egg yolks (from pastured hens), modest amounts
• Grass-fed butter, modest amounts

Caveats

If you're on warfarin or other vitamin K-antagonist anticoagulants, K2 can interfere with the medication. Don't supplement K2 without your prescriber's input.

Bottom line

Buy MK-7. Take 90-180 mcg once daily with your D3. Move on with your life.

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