Vitamin K2 Status: What This Marker Means for Bones and Arteries

Written by Dr. Ryan Kneessi, ND

Quick answer: Vitamin K2 is a family of menaquinones that, along with vitamin K1, activates proteins that help keep calcium in bone and out of artery walls. Because K2 is rarely detectable in blood, status is often judged by inactive vitamin K dependent proteins such as dp-ucMGP, where a higher level generally reflects lower vitamin K status. No single marker is considered a gold standard.

Where does the calcium in your body actually end up? Vitamin K is the nutrient that helps answer that question. It comes in two main forms. Vitamin K1, or phylloquinone, comes mostly from green leafy vegetables, while vitamin K2 is a family of menaquinones found in modest amounts in fermented foods and some animal foods, and also made by bacteria in the gut. Both forms switch on a group of proteins that help keep calcium in bone and out of the walls of blood vessels. Testing vitamin K status is trickier than it sounds, which is why it helps to understand what a result can and cannot tell you. The habits most often discussed around vitamin K are eating leafy greens regularly, including fermented foods if they agree with you, supporting a healthy gut and talking with your provider about any medications that interact with vitamin K.

This article is educational. It explains what the marker reflects and how researchers connect it to the deeper mechanisms of aging, so you can have a more informed conversation with your own provider.

What does a vitamin K2 test actually measure?

According to the NIH Office of Dietary Supplements, vitamin K is rapidly metabolized and excreted, so only low levels are present in the blood and tissues, and vitamin K status is not routinely assessed. A review by Shea and Booth adds an important detail for K2 in particular. Phylloquinone can be measured in circulation and rises with intake, but menaquinones are generally not detected in the blood unless large amounts are eaten. That means a blood level of K2 by itself often says little.

Because of this, researchers often look at the job vitamin K does rather than the vitamin itself. Vitamin K activates proteins such as osteocalcin in bone and matrix Gla protein in blood vessels. When there is not enough vitamin K, more of these proteins circulate in an inactive, undercarboxylated form. A higher level of inactive matrix Gla protein, called dp-ucMGP, is generally read as a sign of lower vitamin K status in the tissues outside the liver. Shea and Booth note that no single marker is considered a gold standard, so the most useful marker depends on the question being asked.

How is vitamin K2 connected to aging and root causes?

Vitamin K sits at an interesting crossroads in how researchers think about aging. Its best-known role outside of blood clotting is keeping calcium where it belongs. Matrix Gla protein is one of the body’s strongest local brakes on calcification of artery walls, and it only works once vitamin K has activated it. Arteries that stiffen and calcify are one of the most visible ways the body changes with age, so this is where most of the interest lies. In a population study of 835 adults published in the Journal of the American Heart Association, higher inactive matrix Gla protein was associated with stiffer arteries.

Vitamin K also connects to chronic low-grade inflammation. In the Framingham Offspring Study, people with higher vitamin K status had lower concentrations of several inflammatory markers as a group. A 2020 review in Nutrients summarized how vitamin K has been studied in a range of age-related conditions linked to inflammation, including cardiovascular disease, osteoarthritis, cognitive decline and frailty. Much of this evidence is observational, so it shows association rather than cause, and the mechanistic links to deeper aging biology are still being worked out.

Because gut bacteria make most of the menaquinones in the body, vitamin K status is also tied to the microbiome. From a root-cause perspective, the first question is why status might be low. Food quality matters most, especially how often leafy greens and fermented foods appear on the plate. Absorption matters too, since vitamin K is fat soluble and depends on healthy digestion and bile flow. The NIH notes that antibiotics, bile acid sequestrants and some weight-loss medications can lower vitamin K levels, and people who take warfarin need consistent vitamin K intake, so changes should always be coordinated with their prescriber. Gut health, movement that loads the bones, sleep and other nutrients that work alongside vitamin K, such as vitamin D and magnesium, all shape where calcium ends up. Genetics also play a part in how each person handles these nutrients.

What does the research show about Vitamin K2 Status?

The Rotterdam Study followed 4,807 adults without a prior heart attack for about 7 to 10 years. People in the highest third of vitamin K2 intake had about 57% lower risk of dying from coronary heart disease (relative risk 0.43) and less severe aortic calcification than those in the lowest third, while vitamin K1 intake showed no link. Diet was measured by questionnaire. (Geleijnse et al., 2004)

In the Chronic Renal Insufficiency Cohort, 3,066 adults with chronic kidney disease had their vitamin K status measured with dp-ucMGP, a protein that rises when vitamin K is low. Those with lower dp-ucMGP had 21 to 29% lower mortality over about 12.8 years, but vitamin K status was not linked with heart events. The findings apply to people with kidney disease. (Shea et al., 2022)

These studies suggest vitamin K status matters for blood vessel health, but trials have not yet shown that raising it improves outcomes.

Related reading

If you would like to explore related topics, my articles on vitamin D and K2 together, small dense LDL and RBC magnesium go deeper. You can also see the specialty tests I commonly recommend on my functional labs page.

Common questions about Vitamin K2 Status

Can a blood test measure vitamin K2 directly?

Usually not well. Menaquinones are generally not detected in the blood unless large amounts are eaten, so researchers often look at inactive vitamin K dependent proteins instead.

What does a high dp-ucMGP level mean?

A higher dp-ucMGP level generally reflects lower vitamin K status in tissues such as blood vessels. In population studies it has been associated with stiffer arteries and more cardiovascular events.

Where does vitamin K2 come from?

Vitamin K2 is found in modest amounts in fermented foods and some animal foods, and bacteria in the gut also make menaquinones.

Sources

This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before making changes to your diet, exercise, supplements, or medications, especially if you are pregnant, nursing, or managing a health condition.