Vitamin K
Vitamin K is a family of fat-soluble compounds required for the activation of proteins involved in normal blood clotting and bone metabolism.
What it does in the body
- Required for activation of several clotting proteins
- Supports vitamin K-dependent proteins in bone
- Acts as a cofactor for vitamin K-dependent carboxylase
Daily reference intake
The U.S. adequate intake is 120 µg/day for adult men and 90 µg/day for adult women.
What can deficiency look like?
- Easy bruising or bleeding in severe deficiency
- Prolonged clotting time
Who may be at higher risk?
- People with fat-malabsorption disorders
- People after some bariatric or intestinal procedures
- Newborns who do not receive vitamin K prophylaxis
Food sources
A varied diet is the first place to look for nutrients. Availability and nutrient content can vary by food, preparation and country.
Food-source note: Vitamin K1 is mainly found in green plants; menaquinones (K2 forms) occur in some fermented and animal foods.
Absorption & practical context
As a fat-soluble vitamin, vitamin K absorption depends on normal bile and fat digestion.
Important interactions
- Warfarin and similar vitamin K antagonists can interact seriously with changes in vitamin K intake
Safety and context
No tolerable upper intake level has been established for vitamin K because toxicity from food and supplements appears low. Anticoagulant users should not make large intake changes without clinical guidance.
Scientific sources
NIH Office of Dietary Supplements — Vitamin K ↗ EU Register of Nutrition and Health Claims ↗Products whose current label lists this nutrient
The entries below are based on current manufacturer label information for the selected market. Compare the stated amount per daily serving and read the official product page before purchasing.