Key points
- MK-7 has a long half-life, so one daily dose maintains steady levels.
- Pair with vitamin D3 to route calcium into bone.
- Contraindicated with warfarin — it directly reverses the drug.
What K2 does that K1 does not
Vitamin K1 from leafy greens is primarily used by the liver for clotting factor synthesis. Vitamin K2, particularly the MK-7 menaquinone form, distributes more widely to bone and vascular tissue.
There it activates two key proteins. Osteocalcin binds calcium into the bone matrix. Matrix Gla protein inhibits calcium deposition in arterial walls. Both require vitamin K-dependent carboxylation to function, which is what K2 supplies.
Why the form and dose matter
MK-4 has a half-life of roughly one hour and is used in Japanese clinical practice at 45 mg daily. MK-7 has a half-life of about 72 hours, so 90-180 mcg once daily maintains a steady serum level. That pharmacokinetic difference is why MK-7 is the form used in most Western supplements.
Absorption is fat-dependent. Take it with a meal containing fat, ideally the same meal as your vitamin D3.
Warfarin: the critical interaction
Warfarin blocks vitamin K epoxide reductase, reducing the regeneration of reduced vitamin K and therefore clotting factor synthesis. Adding vitamin K2 restores substrate for that enzyme and directly reverses the anticoagulant effect.
This can drop the INR into a clot-risk range without any warning symptom. If you take warfarin and want to add K2, it must be done with prescriber knowledge and INR monitoring. The same caution applies to vitamin K1 supplements and to large, sudden changes in leafy-green intake.