Vitamins
Vitamin K1
Also called: phylloquinone, vitamin K
The form of vitamin K in leafy greens, needed for blood clotting.
- Why people take it
- Clotting, bone health.
- What the evidence says
- Deficiency is rare in adults. Newborns get a vitamin K injection at birth.
- How it is usually taken
- Usually 50 to 100 mcg a day in supplements; found in green leafy vegetables. Newborns get an injection at birth.
- Be careful
- Changes how warfarin works: keep intake steady and talk to your doctor.
- Medicines it can interact with
- Vitamin K directly works against warfarin; keep intake steady and tell your doctor before taking any supplement with vitamin K. It does not affect newer blood thinners.
Other vitamins
Common questions
What is Vitamin K1?
The form of vitamin K in leafy greens, needed for blood clotting.
Why do people take Vitamin K1?
Clotting, bone health.
Does Vitamin K1 work?
Deficiency is rare in adults. Newborns get a vitamin K injection at birth.
How much Vitamin K1 do people take?
Usually 50 to 100 mcg a day in supplements; found in green leafy vegetables. Newborns get an injection at birth.
Is Vitamin K1 safe?
Changes how warfarin works: keep intake steady and talk to your doctor.
Does Vitamin K1 interact with medicines?
Vitamin K directly works against warfarin; keep intake steady and tell your doctor before taking any supplement with vitamin K. It does not affect newer blood thinners.
Sources and further reading
Last reviewed 31 October 2026. Written by Satya Babu.
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