Vitamins, minerals and supplements - Vitamin K

Vitamin K has several important functions. For example, it is needed for blood clotting, which means it helps wounds heal properly.

There is increasing evidence that vitamin K is also needed to help build strong bones.

Good sources of vitamin K

Vitamin K is found in:

• green leafy vegetables, such as broccoli and spinach
• vegetable oils
• cereals

Small amounts can also be found in meat and dairy foods.

How much vitamin K do I need?

Adults need approximately 0.001mg a day of vitamin K for each kilogram of their body weight.

For example, someone who weighs 65kg would need 0.065mg a day of vitamin K, while a person who weighs 75kg would need 0.075mg a day.

You should be able to get all the vitamin K you need by eating a varied and balanced diet. 

Any vitamin K that your body does not need immediately is stored in the liver for future use, so you do not need it in your diet every day.

What happens if I take too much vitamin K?

There is not enough evidence to know what the effects might be of taking high doses of vitamin K supplements each day.

What does the Department of Health advise?

You should be able to get all the vitamin K you need by eating a varied and balanced diet. If you take vitamin K supplements, do not take too much because this might be harmful.

Taking 1mg or less of vitamin K supplements a day is unlikely to cause any harm.