Ingredients explained

Vitamin K2 (MK-7): the guide

Written by the NATURELO nutrition teamReviewed by Milan ShahLast reviewed 26 September 20263 min read

The short answer

Vitamin K2 contributes to the maintenance of normal bones and to normal blood clotting. It is most often sold paired with vitamin D3: vitamin D helps your body absorb calcium, and vitamin K2 plays a part in how bone uses it, so the two are combined for bone support. The form to look for is MK-7, which stays active in the body longer than the shorter MK-4. One caveat: if you take a blood-thinning medicine like warfarin, vitamin K affects clotting, so talk to your clinician before starting it.

  • K2 contributes to the maintenance of normal bones and to normal blood clotting.
  • MK-7 is the longer-lasting form and the one usually chosen.
  • D3 and K2 are paired for bone support, because D3 handles calcium absorption.
  • If you are on warfarin or another anticoagulant, speak to your clinician first.
Broccoli, avocado, green beans and leafy greens on a white table

What does vitamin K2 do?

In the terms UK rules allow, vitamin K contributes to the maintenance of normal bones and to normal blood clotting. Those are the two authorised descriptions, and they mark the limit of what K2 should be sold for. You will read bigger claims about arteries and the heart in some corners of the internet. Those are not authorised here, and we will not make them. The settled evidence and the rules both sit with bones and clotting.

MK-7 versus MK-4

Vitamin K2 comes in a few chemical forms, and the two you will see named are MK-4 and MK-7. The practical difference is how long they last in the body. MK-7 has a longer half-life, which means a single daily dose keeps working for longer, so it is the form most supplements are built around, ours included. MK-4 is shorter-acting and usually needs more frequent, higher dosing to do the same job. For a once-a-day supplement, MK-7 is the sensible choice.

Why D3 and K2 are paired

Most people come to K2 with this question. Vitamin D helps your body absorb calcium from food. Vitamin K2 then contributes to the maintenance of normal bones. Pairing the two supports bone from both directions in a single capsule, which is why D3 and K2 are so often sold together. If bone support is your reason for taking vitamin D, a D3 and K2 combination is a reasonable and popular pick. It also suits anyone taking a higher-dose vitamin D who wants K2 alongside it.

The warfarin caution

Because vitamin K contributes to normal blood clotting, it interacts with blood-thinning medicines that work against vitamin K, warfarin being the common one. K2 is not dangerous in this situation, but the amount needs to stay consistent, and the decision to start it belongs with the clinician managing your medication. If that applies to you, ask first. Otherwise K2 is a well-tolerated everyday nutrient.

Which should you choose?

For most people wanting bone support, a D3 and K2 combination in the MK-7 form is the straightforward choice. Our vegan D3 and K2 provides 5000 IU of vitamin D3 from lichen with 120 micrograms of K2 as MK-7, so you get the longer-lasting form paired with a meaningful dose of D3. If you want the detail on the D3 side, the vitamin D3 guide covers dose and the safe upper level.

FAQ

Questions people ask

What does vitamin K2 do?

It contributes to the maintenance of normal bones and to normal blood clotting.

What is the difference between MK-4 and MK-7?

MK-7 lasts longer in the body, so it suits a once-daily dose. MK-4 is shorter-acting and usually needs more frequent dosing.

Should I take vitamin D3 with K2?

If bone support is your goal, the pairing makes sense, because D3 helps absorb calcium and K2 contributes to normal bones.

Can I take K2 with warfarin?

Speak to your clinician first. Vitamin K affects blood clotting, so it interacts with warfarin and the amount needs to stay consistent.

Keep reading

Related guides

Vitamin D3: how much to take, and is 5000 IU too much?The NHS baseline, D3 versus D2, vegan D3 from lichen, and an honest look at the safe upper level and the 5000 IU question.
Read the guide →Calcium supplements: how much you need and which formDo you need a calcium supplement? How much calcium you need, which form to choose, the food-first truth, and the plant-based marine-algae option.
Read the guide →

The NATURELO nutrition team

Reviewed by Milan Shah, Certificate in Plant-Based Nutrition, T. Colin Campbell Center for Nutrition Studies (eCornell).

This guide is general information, not a substitute for advice from your GP, midwife or pharmacist.