Vitamin K (K1 and K2)
K1 and K2, MK-4 and MK-7, D3 with K2: the forms of vitamin K, how much supplements contain and who needs to be careful with it.
- Vitamin K contributes to normal blood clotting.
- Vitamin K contributes to the maintenance of normal bones.
The claims apply to a product whose daily dose provides at least 15 % of the reference intake (75 µg).
A varied and balanced diet and a healthy lifestyle are important.
What it is
Vitamin K is a group of fat-soluble vitamins. K1 (phylloquinone) is in green leafy vegetables. K2 (menaquinones) is in fermented foods such as Japanese natto, and in some cheeses. The EU labelling reference intake is 75 µg a day.
Vitamin K has two authorised claims in the European Union — listed above. They apply to products whose daily dose provides at least 11.25 µg (15 % of the reference intake).
MK-7 and MK-4
In supplements K2 is most often MK-7 (from natto or synthesised), usually 45–200 µg. MK-4 is rarer and comes in different doses. Many products pair K2 with vitamin D3 — the vitamin D page has more.
Who should be careful
People on blood thinners that act against vitamin K (such as warfarin) must not start vitamin K without agreeing it with a doctor: it changes how those medicines work. Capsules are usually taken with a meal containing fat.
Frequently asked questions
How is K1 different from K2?
K1 is in green vegetables, K2 in fermented foods and some cheeses. Supplements more often use K2 as MK-7.
Can I take vitamin K while on warfarin?
Only with a doctor's agreement: vitamin K changes how such medicines work.
Why is K2 paired with D3?
It is a common combination among makers. Each vitamin has its own authorised claims in the EU, and we show them when the doses are enough.
Vitamin D & K2 in the shop
