Comparison guide
Which vitamin K should you take?
K1 is the dietary form that runs blood clotting; K2 comes as MK-7 and MK-4, which differ mainly in how long they stay in the blood. The bone and artery claims made for all three are far weaker than the marketing suggests, and every form interacts with warfarin.
The options, compared
| Option | Evidence | Best for | The honest note | |
|---|---|---|---|---|
| Vitamin K1 | Limited evidence | Clotting needs, usually covered by diet | Essential for coagulation and supplied mostly by leafy greens and vegetable oils, but 5 mg/day for up to four years did not change bone mineral density. | View |
| Vitamin K2 (MK-7) | Limited evidence | The practical K2 choice | A half-life of roughly three days suits once-daily dosing, and one trial found slower bone loss at 180 mcg/day, but the trial built to test vascular calcification was flat. | View |
| Vitamin K2 (MK-4) | Limited evidence | Not worth it at supplement doses | The Japanese fracture data used a 45 mg/day prescription dose; at supplement doses its half-life of hours means it barely registers in the blood. | View |
Our verdict
K1 from food covers clotting needs for most people. If you want a K2 supplement, MK-7 is the practical form, but treat its bone and artery benefits as unsettled, and skip MK-4 capsules. If you take warfarin or another vitamin K antagonist, do not start or stop any of them without your prescriber or anticoagulation clinic.