Vitamin K1 (Phylloquinone)

The leafy-green form of vitamin K, specialized for blood clotting.

Mechanisms, studies and evidence grades for each claim above.

Core mechanism

Vitamin K1 enables γ-carboxylation of clotting factors, which allows them to bind calcium — the step that makes normal clotting possible.

Blood coagulation

Activates clotting factors II (prothrombin), VII, IX, and X.¹ Without K1, these factors remain undercarboxylated and inactive, impairing clotting and raising bleeding risk.

Liver

Vitamin K1 is preferentially taken up by the liver, where it supports synthesis and activation of clotting factors.²

Deficiency effects

Coagulopathy — easy bruising, bleeding gums, prolonged bleeding time.¹

Transport / distribution

Primarily transported to and used in the liver; shorter half-life than K2.²

Interaction with vitamin K2

K1 primarily supports clotting (liver-focused); K2 regulates calcium placement in peripheral tissues (bone, arteries) — see Vitamin K2. The Metabolic Health hub's supplement note on K2 (MK-7 needing daily dosing, not intermittent) is specific to K2's longer half-life and doesn't carry over to K1.

Intake

Roughly 90–120 mcg/day.

Top foods

• Spinach
• Kale
• Broccoli
• Plant oils

Key insight

Vitamin K1 is specialized for activating clotting factors in the liver, making it essential for maintaining normal blood coagulation.¹

References