Vitamin
Vitamin K
Vitamin K is essential for blood clotting and helps keep bones healthy. It is found in green leafy vegetables, and deficiency is uncommon in adults.
What it is
Vitamin K is a fat-soluble vitamin that exists mainly as K1 (from plants) and K2 (from some animal foods and made by gut bacteria).
What it does
It is needed for blood to clot properly, so that wounds stop bleeding, and it also plays a part in keeping bones healthy.
Good sources
Green leafy vegetables such as broccoli, spinach and kale, vegetable oils, and some cereal grains; smaller amounts come from meat and dairy.
Deficiency and who is at risk
Deficiency is rare in healthy adults but can cause easy bruising and bleeding. Newborn babies are given vitamin K at birth because they have low levels and are at risk of a serious bleeding disorder.
Balance
Can you have too much?
Vitamin K from food is not known to be harmful. However, it interacts with blood-thinning medicines such as warfarin, so people taking these should keep their intake steady rather than changing it suddenly.
Education and reference only. This is general nutrition information, not personal advice, and does not give doses. Ask a pharmacist, GP or registered dietitian before starting supplements, especially with a health condition or in pregnancy.
Answers
Vitamin K: frequently asked questions
Why are newborn babies given vitamin K?
Babies are born with very low vitamin K, which puts them at risk of a rare but serious bleeding condition. A dose of vitamin K at birth, by injection or by mouth, prevents this.
Can I eat green vegetables if I take warfarin?
Yes, but keep your intake consistent rather than suddenly eating a lot more or less, because vitamin K affects how warfarin works. Your anticoagulation team can advise.
Related
More on vitamins and nutrition
Sources
Where this is drawn from
- NHS — Vitamins and minerals
- British Dietetic Association (BDA)
- UK Scientific Advisory Committee on Nutrition (SACN)
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