Is Vitamin K2 Deficiency Sabotaging Your Bones and Heart?

When I first wrote about vitamin K2 deficiency, the research was still being treated as a curiosity outside of bone and clotting circles. That’s changed. In the last two years alone, we’ve gotten a pediatric study linking low K2 status to short stature, a mechanistic study showing exactly how K2 controls bone breakdown at the cellular level, a fresh meta-analysis on K2 and postmenopausal bone turnover, and a post-hoc analysis showing K2 lowers blood pressure in postmenopausal women with stiff arteries. This is not a niche nutrient anymore — it’s one I test for constantly in clinic, and I still find deficiency in people eating what they’d call a “healthy diet.” Let’s get into why.

What Is Vitamin K2, and How Is It Different From K1?

Vitamin K is a fat-soluble vitamin best known for its role in blood clotting. But that’s really vitamin K1’s job. Vitamin K2 (menaquinone) is a distinct sub-family of vitamin K, distinguished by side chains that range from 1 to 14 units long — hence names like menaquinone-4 (MK-4) and menaquinone-7 (MK-7), the form most commonly supplemented and the one used in the majority of the newer clinical trials I reference below.

Functions of vitamin K2 that go beyond clotting include:

• Calcium metabolism — directing calcium into bone and out of soft tissue and arteries
• Bone strength and turnover
• Arterial health and vascular flexibility
• Brain and cognitive health — although the mechanism isn’t fully understood, vitamin K2 status has been linked to brain and eye health in recent research
• Proper blood clotting

Deficiency of vitamin K2 at any age increases the risk of bone fractures, osteoporosis, heart disease, and atherosclerosis.

A 2026 mechanistic study in Bone Research mapped out one reason K2’s bone role is so specific: vitamin K-dependent carboxylation in osteoblasts (the cells that build bone) regulates bone resorption through a protein called GAS6 — meaning K2 status doesn’t just help build bone, it helps control how fast bone is broken back down.¹ That’s a more precise mechanism than we had access to when I first wrote this post.

Just How Common Is Vitamin K2 Deficiency, Globally?

This is still the part that surprises people most. Research suggests that up to 97% of Western populations have a deficiency or insufficiency of vitamin K2.² That figure comes from a vitamin K2 ingredient supplier, which is worth noting for transparency — though it’s also worth remembering that most nutrient research, pharmaceutical or otherwise, is funded by the companies with a stake in the ingredient, and that alone isn’t a reason to dismiss it. This number lines up with what I see clinically and with the underlying academic literature: healthy children and adults routinely show markedly low levels of undercarboxylated osteocalcin, a direct marker of inadequate vitamin K2 status, even on diets that look nutritionally complete on paper.

Vitamin K2 Deficiency and Bone Fracture Risk

The bone data has only gotten stronger. A 2025 systematic review and meta-analysis in Frontiers in Endocrinology looked specifically at vitamin K2 supplementation and bone turnover markers in postmenopausal women with osteoporosis, adding meaningful weight to the case for K2’s role in this population.³

Older but still relevant regional data backs this up: in Poland, children aged 5–15 admitted to the hospital with low-energy bone fractures had significantly lower vitamin K markers than healthy children. Findings from Europe found undercarboxylated factor II — another vitamin K deficiency marker — was low in 36% of elderly hip fracture patients, and that number rose to 64% after patients were held off food before and after surgery, which tells you how quickly status can decline.

New research out of China also connects vitamin K2 status to childhood growth: a 2025 cross-sectional study of 730 children found vitamin K2 deficiency associated with short stature, an association the authors say warrants longitudinal follow-up to confirm causality.⁴ This adds to what I’ve written before about why kids specifically are at risk — see 5 Reasons Why Kids Need a Vitamin K2 Supplement.

Vitamin K2 Deficiency and Heart Disease Risk

South Asians are at elevated risk for heart disease, and a study following roughly 700 people from India, Pakistan, Bangladesh, Sri Lanka, Nepal, and Bhutan (part of the long-running MASALA study) found that coronary artery calcification — closely tied to vitamin K deficiency — increased cardiovascular risk over five years to a degree comparable to white men, the group with historically the highest heart disease rates.

In peritoneal dialysis patients in China, vitamin K2 deficiency nearly doubled the risk of heart-related mortality, and those with the lowest status had almost three times the risk of events like heart attack, alongside higher inflammation markers. I go deeper on the mechanism — including K2’s role in mitochondrial and skeletal muscle function — in Improve Your Heart Health with Vitamin K2. Since heart muscle is so mitochondria-dense, it’s also worth reading how these two nutrients work together in my posts on CoQ10/ubiquinol and mitochondrial health.

What’s new here is interventional, not just observational. A post-hoc analysis of a one-year, placebo-controlled trial in women with low vitamin K status found that 180 mcg/day of MK-7 significantly reduced vascular stiffness in postmenopausal women, and among those with the highest baseline arterial stiffness, MK-7 also lowered blood pressure and improved arterial distensibility.⁵ That’s a meaningful upgrade from association to a measured, dose-specific outcome.

There’s also emerging interest in vitamin K2 and cognitive health. A 2025 review on the epigenetic potential of vitamin K2 in brain health summarized evidence that long-term low vitamin K intake impairs hippocampal-dependent cognitive function in animal models, adding to earlier signals connecting K2 status to brain and eye health.⁶ I’ve also covered emerging research on K2 and the gut in Do You Need K2 Vitamins for Colon Health?

Food Sources of Vitamin K2

True vitamin K2 is concentrated in a narrow list of foods: fermented foods like natto (by far the richest source), certain aged cheeses, egg yolks, and organ meats and fatty cuts from pasture-raised, grass-fed animals. If you’re building your diet around these sources, a few posts I’ve written cover them in more depth: organ meats, liver, grass-fed beef, and eggs. Vitamin K2 is also fat-soluble, so absorption depends on adequate bile flow and fat digestion — something worth knowing if you also deal with sluggish digestion; see my posts on ox bile and TUDCA. For a broader outside resource on the food-source problem specifically, Chris Masterjohn has a thorough write-up worth a look.

Why Is Vitamin K2 Deficiency So Common?

The core problem hasn’t changed: food sources of true vitamin K2 are limited, concentrated mostly in fermented foods like natto and certain aged cheeses, and in animal products from pasture-raised animals. Most people simply aren’t eating enough of these foods regularly.

A few other contributing factors I regularly explain to clients:

• The RDA for vitamin K was set based on clotting needs, using K1 — it was never designed around K2’s role in bone and artery health.
• Vitamin K1 from leafy greens absorbs poorly, and the body’s ability to convert K1 to K2 is limited.
• Perioperative fasting and illness can rapidly worsen status, as the hip fracture data above shows.
• Gut bacteria were once thought to supply meaningful K2, but restriction studies show the digestive tract’s contribution is much smaller than previously assumed.

Signs of Vitamin K Deficiency

Keep in mind that none of these signs are guaranteed to show up even with genuinely low vitamin K2 status — that’s part of why testing, not guessing, matters here.

• Easy bruising
• Excessive bleeding from wounds, punctures, injections, or surgical sites
• Heavy menstrual periods
• Bleeding from the GI tract
• Blood in urine or stool
• Increased prothrombin time (PT/INR)

Newborns routinely receive supplemental vitamin K because deficiency bleeding, while rare, can be life-threatening in infants — and a 2025 review in Nutrition Reviews underscored that late vitamin K deficiency bleeding in infancy remains a preventable but persistent risk, reinforcing the need for consistent prophylaxis protocols.⁷

Beyond infancy, suspicion for deficiency should be higher in people with malnutrition or malabsorption (including digestive disease), those who are chronically ill (including cancer or dialysis patients), and anyone on medications that interfere with vitamin K, including:

• Anticonvulsants (carbamazepine, phenytoin, barbiturates)
• Antituberculosis drugs (isoniazid, rifampicin)
• Certain antibiotics (cephalosporins)
• Vitamin K antagonists (warfarin) — where INR interactions are critical to monitor with your prescriber

Supplementing Vitamin K2

The RDA for vitamin K predates most of what we now know about K2 specifically, so it isn’t a useful target if bone and artery health are your goal. Based on the clinical trial data above, 180 mcg/day of MK-7 is the dose most consistently studied and used in adults for bone and cardiovascular markers; pediatric dosing in the research runs closer to 45 mcg/day, and should be guided by a practitioner.

I recommend working with a practitioner to test your vitamin K status rather than guessing at a dose — test not guess, as I always say — particularly if you’re on any of the medications listed above. Vitamin K2 and vitamin D3 work together on calcium metabolism, so if you’re testing one, it’s worth testing the other; see my breakdown in Vitamin D Test Cost: Is It Worth the Price? For a closer look at how to choose a quality K2 product, I’ve reviewed brands in The Best Vitamin K2 Supplement Brands. You can also browse practitioner-grade options through my Fullscript store.

Can’t I Just Supplement Vitamin K1 Instead?

I wish it were that simple, but vitamin K1 isn’t even as effective at supporting clotting as K2, doesn’t absorb as well, and doesn’t meaningfully impact bone or heart health the way K2 does. If bone and cardiovascular support are the goal, K1 alone won’t get you there.

Is Vitamin K2 Supplementation Safe?

Vitamin K2 has a strong safety profile at studied doses. The one firm caveat: if you’re on blood-thinning medication such as warfarin, talk to your prescriber before adding any form of vitamin K, since it can interact with anticoagulant dosing and INR monitoring.

Vitamin K2 Deficiency: The Bottom Line

Vitamin K2 deficiency, as measured by blood markers, is linked to increased heart disease mortality and continues to show up as a global bone health problem — and the newest research adds childhood growth and postmenopausal vascular health to the list of areas affected. Given how common insufficient status appears to be, even on a solid diet, this is a nutrient worth testing rather than assuming you’re covered.

Frequently Asked Questions

What is the difference between vitamin K1 and K2?
Vitamin K1 primarily supports blood clotting and is found in leafy greens, but it absorbs poorly and does not meaningfully support bone or heart health. Vitamin K2 (menaquinone) supports clotting as well as calcium metabolism, bone strength, and arterial health.

How common is vitamin K2 deficiency?
Industry estimates suggest up to 97% of Western populations have a deficiency or insufficiency of vitamin K2, and clinical markers like elevated undercarboxylated osteocalcin show up even in people eating diets that appear nutritionally adequate.

What is a good vitamin K2 dose for adults?
Clinical trials most consistently use 180 micrograms per day of MK-7 for bone and cardiovascular support in adults. Work with a practitioner to confirm the right dose and form for your situation.

Is vitamin K2 safe to take with blood thinners?
Anyone on blood-thinning medication such as warfarin should talk to their doctor before supplementing with any form of vitamin K, since it can affect INR monitoring and anticoagulant dosing.

Can vitamin K2 deficiency affect children?
Yes. A 2025 study of 730 children found an association between low vitamin K2 status and short stature, and newborns are routinely given supplemental vitamin K to prevent deficiency bleeding.

References
1. Pata M, Pham DNT, Lacombe J, et al. Vitamin K-dependent carboxylation in osteoblasts regulates bone resorption through GAS6 in male mice. Bone Res. 2026;14(1):48.
2. Gnosis by Lesaffre. Vitamin K2 and active folate may reduce risk of cardiovascular disease. NutritionInsight, 2026.
3. Zhang Z, Li Y, Li J, et al. The effect of vitamin K2 supplementation on bone turnover biochemical markers in postmenopausal osteoporosis patients: a systematic review and meta-analysis. Front Endocrinol. 2025;16:1703116.
4. Shen Y, Shi G, Wen S, Luo W, Wang K. Vitamin K2 deficiency associated with short stature in children: a cross-sectional study. BMC Pediatr. 2025;25(1):348.
5. de Vries F, Bittner R, Maresz K, et al. Effects of One-Year Menaquinone-7 Supplementation on Vascular Stiffness and Blood Pressure in Post-Menopausal Women. Nutrients. 2025;17(5):815.
6. Fuso A, et al. The epigenetic potential of vitamin K2 in brain health. Nutr Neurosci. 2025.
7. Perrone S, Beretta V, Petrolini C, Scarpa E, De Bernardo G, Buonocore G. Late Vitamin K Deficiency Bleeding in Infancy: The Time to Ensure Effective Prevention. Nutr Rev. 2025.