MK-7 lasts longer in the body and is the usual supplemental form at lower doses; MK-4 is used at higher doses in some research. MK-7 is the practical everyday choice.

Should I take it with vitamin D?

They're commonly combined on the theory that K2 directs the calcium vitamin D helps absorb into bone. It's a reasonable pairing, though the long-term outcome evidence is still building.

Is it safe with blood thinners?

If you take warfarin, do not add vitamin K without your provider's guidance, as it directly opposes the drug. Discuss any anticoagulant with your provider first.

Vitamin K2: Benefits, Dosing & Evidence

What it is

Vitamin K2 is part of the vitamin K family and plays a role in activating proteins that guide calcium into bones and away from arteries. It's found in fermented foods and some animal products, and often paired with vitamin D and calcium.

How it works

Vitamin K2 activates proteins that manage where calcium goes in the body. One (osteocalcin) helps bind calcium into the bone matrix; another (matrix Gla protein) helps keep calcium out of arteries and soft tissue. This 'calcium traffic control' is the rationale for pairing K2 with vitamin D and calcium — the idea being to steer absorbed calcium toward bone.

What it's been studied for

Taken to support bone health, usually alongside vitamin D and calcium.

What the evidence shows

A meta-analysis found vitamin K2 supported bone density in postmenopausal osteoporosis. It's best thought of as a partner to calcium and vitamin D rather than a standalone.

Who should consider it

It's mainly taken by people focused on bone health, usually alongside vitamin D and calcium, and by those interested in cardiovascular calcium balance. Because it partners with vitamin D, it's often chosen by people already supplementing D. Anyone on the blood thinner warfarin must not add vitamin K without medical guidance.

Amounts commonly studied

Studies use varying amounts; MK-7 is commonly supplemented at roughly 90-180 mcg per day, MK-4 at higher amounts.

How to take it

MK-7 is the common supplemental form, typically around 90-180 mcg per day; it has a longer action in the body than MK-4. It's fat-soluble, so take it with a meal, and it's frequently combined with vitamin D3 in one product. Consistency matters more than timing.

Forms & absorption

MK-7 has a longer action in the body and is the common supplemental form; MK-4 is used at higher doses in some research. Often combined with vitamin D3.

Food sources

K2 (menaquinone) is found in fermented foods — natto (fermented soybeans) is by far the richest source — plus some cheeses, egg yolks, and animal products. K1, the more common dietary form, comes from leafy greens and converts to K2 only in small amounts.

Safety & interactions

Generally safe. Important exception: vitamin K interacts with blood-thinning medication like warfarin, so anyone on those drugs must talk to their provider before using it.

Myths & what it won't do

Myth: K2 alone builds strong bones. Reality: it's best understood as a partner to calcium and vitamin D, not a standalone bone builder. Myth: K2 is dangerous with any blood thinner. Reality: the interaction is specifically with warfarin (a vitamin K antagonist); newer direct oral anticoagulants aren't affected the same way — but always confirm with your provider.

Common questions

MK-4 or MK-7?: MK-7 lasts longer in the body and is the usual supplemental form at lower doses; MK-4 is used at higher doses in some research. MK-7 is the practical everyday choice.
Should I take it with vitamin D?: They're commonly combined on the theory that K2 directs the calcium vitamin D helps absorb into bone. It's a reasonable pairing, though the long-term outcome evidence is still building.
Is it safe with blood thinners?: If you take warfarin, do not add vitamin K without your provider's guidance, as it directly opposes the drug. Discuss any anticoagulant with your provider first.

The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.

Vitamin K2