Vitamin K (Phylloquinone / K1)
Vitamin K1, or phylloquinone, is the main dietary form of vitamin K, found largely in leafy green vegetables. It is essential for normal blood clotting and also supports bone health.
Vitamin K allows your body to form the proteins needed to stop bleeding and to help build bone. Because it is fat-soluble, its status is influenced by fat absorption and dietary intake. Blood clotting is more often assessed through tests like PT/INR, but a direct K1 level gives a picture of intake and status.
A high vitamin K1 level typically reflects recent dietary or supplement intake. Vitamin K from food and supplements has not been associated with toxicity in the way some other fat-soluble vitamins can be, so a high value is usually not a safety concern. However, vitamin K interacts strongly with blood-thinning medications like warfarin, so consistency matters if you take one.
A low vitamin K1 level suggests limited intake or poor fat absorption and can, over time, affect clotting and bone-related proteins. It is more likely with very low vegetable intake or malabsorption.
Labs provide a reference range, and clotting is often assessed separately. If you take a blood thinner, a clinician can advise on keeping vitamin K intake steady.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.