Vitamin K (menaquinone)
Useful mainly for people supporting bone and arterial health, or correcting low vitamin K2 intake.
Quick decision guide
May help most
people supporting bone and arterial health, or correcting low vitamin K2 intake
Common dosing range
45-180 mcg/day MK-7 (or 1.5-5 mg MK-4)
When to expect effects
Months (bone/vascular endpoints)
Watch out for
Do not start if on warfarin without telling the prescriber.
What is it
Vitamin K2, or menaquinone, is a fat-soluble vitamin that activates proteins involved in blood clotting, bone metabolism, and the regulation of calcium deposition in arteries and soft tissues. It is found mainly in fermented foods and animal products.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
vitamin k deficiency / clotting cofactor support Strong Evidence | Restores normal clotting factor activation | people with inadequate vitamin K status | Days |
bone density support Limited Evidence | Improved osteocalcin carboxylation; small/uncertain BMD effect | postmenopausal adults at risk of bone loss, often alongside vitamin D and calcium | Months |
arterial calcification Limited Evidence | Reduced inactive matrix Gla protein; uncertain effect on calcification | adults interested in vascular calcium handling | Months |
vitamin k deficiency / clotting cofactor support
- Effect
- Restores normal clotting factor activation
- Best fit
- people with inadequate vitamin K status
- Time
- Days
bone density support
- Effect
- Improved osteocalcin carboxylation; small/uncertain BMD effect
- Best fit
- postmenopausal adults at risk of bone loss, often alongside vitamin D and calcium
- Time
- Months
arterial calcification
- Effect
- Reduced inactive matrix Gla protein; uncertain effect on calcification
- Best fit
- adults interested in vascular calcium handling
- Time
- Months
Evidence for 3 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
vitamin k deficiency / clotting cofactor support
Corrects deficiencyVitamin K is an essential cofactor for gamma-glutamyl carboxylase, which activates clotting factors made in the liver. Adequate intake is required for normal coagulation, a well-established physiological role. This is a deficiency-correction function rather than a supraphysiologic benefit.
Bottom line: Vitamin K is required to activate clotting factors; adequate intake supports normal coagulation.
bone density support
Biomarker supportK2 activates osteocalcin, which helps bind calcium to bone, and supplementation increases carboxylated osteocalcin. Some trials (notably high-dose MK-4 research) suggest benefit for bone density or fracture risk, but results are mixed and much of the strongest data is from specific populations. Treat bone-density support as probable but not definitively established for fracture prevention.
Bottom line: Improves osteocalcin activation and likely supports bone density, though fracture data are mixed.
Evidence is mixed
High-dose MK-4 trials in some populations show fracture/BMD benefit, but broader and MK-7 data are inconsistent.
arterial calcification
Biomarker supportK2 activates matrix Gla protein, which inhibits calcium deposition in arteries, and supplementation lowers circulating inactive (dephospho-uncarboxylated) matrix Gla protein. Whether this translates into reduced arterial calcification or cardiovascular events is not established, with trials showing inconsistent imaging outcomes. This is a biomarker effect, not a demonstrated reduction in vascular disease.
Bottom line: K2 improves a vascular calcium-handling biomarker, but clinical cardiovascular benefit is unproven.
Evidence is mixed
K2 reliably activates matrix Gla protein, yet imaging trials of arterial calcification show inconsistent results.
How it works
How to take it
What to track
3 commercial forms
Compare the main delivery options and what they’re best suited for.
MK-4 (menaquinone-4)
The form used in much of the bone-health research from Japan, typically at 45 mg per day. Short half-life requires multiple doses, but it has the strongest evidence base for bone outcomes.
shorter half-life, higher doses needed
MK-7 (menaquinone-7)
Sourced from natto (fermented soybeans) or produced commercially. Long half-life (about 72 hours) makes once-daily dosing at 45 to 180 mcg sufficient.
long half-life, low-dose effective
MK-9
A longer-chain form found in fermented cheese. Less commonly available as a supplement.
found in some fermented dairy
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Who should avoid it
- people on warfarin should not start without prescriber guidance
Pregnancy & breastfeeding
Pregnant and breastfeeding women have similar requirements as other adults; newborns receive a vitamin K injection at birth.
Interactions
vitamin K opposes their effect; sudden intake changes destabilize INR
may interfere with vitamin K function in some people
Protocols featuring Vitamin K (menaquinone)
Evidence-backed routines where Vitamin K (menaquinone) plays a role.
Heart Health Foundation
cardiovascular
Cardiovascular disease is the leading killer of adults globally. The supplement category for heart health is overrun with marketing, but a handful of compounds have legitimate long-term human evidence: omega-3 EPA/DHA, CoQ10, magnesium, vitamin K2, and taurine. None of these replace evidence-based pharmaceutical therapy (statins, ACE inhibitors, etc.) when one is medically indicated. They DO function well as a preventive baseline for adults without active cardiovascular disease, and as complements to medical therapy. This protocol is for cardiovascular maintenance and primary prevention — see Cholesterol Support or Blood Pressure Support for goal-specific protocols.
Corticosteroid Companion
medication
Long-term oral corticosteroids (prednisone, methylprednisolone, dexamethasone) are life-changing — and often life-saving — for autoimmune disease, severe asthma, COPD, transplant rejection prevention, and inflammatory conditions. They''re also the strongest documented cause of secondary osteoporosis. Within the first 3-6 months of chronic glucocorticoid therapy, adults can lose 6-12% of bone mineral density at the lumbar spine. The 2017 American College of Rheumatology guidelines on glucocorticoid-induced osteoporosis recommend calcium 1000-1200 mg + vitamin D 600-800 IU for EVERY adult on chronic glucocorticoids, regardless of fracture risk. Steroids also drive muscle wasting (type II fiber atrophy via the ubiquitin-proteasome and autophagy pathways), magnesium and potassium depletion, blood sugar dysregulation, sleep disruption, and mood changes. This protocol is for adults on LONG-TERM oral corticosteroid therapy (typically ≥3 months or anticipated ≥3 months). It is NOT for short steroid bursts — a 5-day prednisone taper for poison ivy or an asthma flare doesn''t warrant this full companion stack. It is also NOT for inhaled corticosteroids (ICS for asthma/COPD), which have much lower systemic absorption. The goal: address the documented downstream complications of chronic glucocorticoid therapy, in coordination with the prescriber who manages your underlying condition. CRITICAL: this protocol does NOT replace any prescribed bone-protection medication (bisphosphonates, denosumab, teriparatide). For moderate-to-high fracture risk, ACR guidelines recommend prescription antifracture therapy IN ADDITION to calcium + vitamin D. Discuss DEXA scan and FRAX score with your prescriber.
Bone Density Support
longevity
Bone density peaks in the late twenties and declines gradually thereafter — accelerating sharply at menopause for women and in the seventies for men. Osteoporosis affects roughly half of women and a quarter of men over 50 and is one of the largest preventable contributors to disability and mortality in later life (hip fractures carry a 20-30% one-year mortality rate). The supplement category is dominated by calcium marketing, but calcium alone is insufficient — vitamin D3, vitamin K2, magnesium, and adequate protein matter as much or more. This stack supports lifelong bone health. It is preventive, not therapeutic — confirmed osteoporosis requires medical management (typically bisphosphonates, denosumab, or romosozumab), and supplements are complementary to those treatments.
Autoimmune Foundation
autoimmune
Autoimmune diseases affect roughly 24 million Americans across 80+ conditions: rheumatoid arthritis, lupus, multiple sclerosis, inflammatory bowel disease (Crohn''s, UC), psoriasis, Hashimoto''s, type 1 diabetes, celiac, Sjögren''s, and dozens more. They share core pathology: the immune system mistakenly attacks the body''s own tissues, driven by genetic predisposition + environmental triggers (infections, gut microbiome dysbiosis, stress, certain medications, sometimes specific exposures). The modern treatment revolution is biologic therapy (DMARDs: methotrexate, sulfasalazine; biologics: adalimumab, infliximab, etanercept, secukinumab, dupilumab; small molecules: tofacitinib, etc.) — these are genuinely transformative for moderate-to-severe disease. This protocol is a FOUNDATIONAL baseline for adults with an autoimmune diagnosis — NOT a substitute for proper rheumatology, gastroenterology, neurology, or endocrinology care. It targets the universal anti-inflammatory and immune-modulating pathways that affect every autoimmune patient: vitamin D (where deficiency is strongly associated with autoimmune disease activity), omega-3 EPA (anti-inflammatory eicosanoid shift), curcumin (NF-kB inhibition), NAC (glutathione support for oxidative stress), and vitamin K2 (mineral metabolism and growing evidence for inflammatory modulation). CRITICAL: Beware "autoimmune cure" marketing. There''s a substantial wellness-industry ecosystem promising that diet, supplements, or "leaky gut protocols" can reverse autoimmune disease. The honest evidence: lifestyle + supplements measurably reduce disease activity and symptom severity but do NOT replace immunomodulator therapy in moderate-to-severe disease. Don''t stop your DMARD or biologic based on supplement marketing.
Food sources
| Food | Amount | %DV |
|---|---|---|
| Natto (fermented soybeans), 3 oz | 850 mcg K2 | — |
| Hard cheese (gouda), 1 oz | 20 to 25 mcg K2 | — |
| Soft cheese (brie), 1 oz | 15 mcg K2 | — |
| Egg yolk, 1 large | 32 mcg K2 | — |
| Chicken thigh, 3 oz cooked | 10 mcg K2 | — |
| Butter, 1 Tbsp | 1 mcg K2 | — |
| Sauerkraut, 1/2 cup | 8 mcg K2 | — |
Natto (fermented soybeans), 3 oz
- Amount
- 850 mcg K2
- %DV
- —
Hard cheese (gouda), 1 oz
- Amount
- 20 to 25 mcg K2
- %DV
- —
Soft cheese (brie), 1 oz
- Amount
- 15 mcg K2
- %DV
- —
Egg yolk, 1 large
- Amount
- 32 mcg K2
- %DV
- —
Chicken thigh, 3 oz cooked
- Amount
- 10 mcg K2
- %DV
- —
Butter, 1 Tbsp
- Amount
- 1 mcg K2
- %DV
- —
Sauerkraut, 1/2 cup
- Amount
- 8 mcg K2
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
What is the difference between K1 and K2?⌄
K1 (phylloquinone) comes mainly from leafy greens and is used by the liver for clotting factors. K2 (menaquinone) comes from fermented foods and animal products and is preferentially used in bone and arteries.
Which is better, MK-4 or MK-7?⌄
MK-7 has a longer half-life and is easier to dose once daily. MK-4 has more research at high doses for bone health but requires multiple daily doses.
Can I take K2 with warfarin?⌄
Only with your prescriber's guidance. Vitamin K opposes warfarin's effect, and any change in intake — including supplements — can destabilize anticoagulation.
Should I take K2 with vitamin D?⌄
Many people pair them. Vitamin D promotes calcium absorption; K2 helps direct calcium to bone rather than arteries. The combination is reasonable but not strictly necessary.
How much K2 do I need?⌄
There is no separate RDA for K2. Supplemental doses of 90 to 180 mcg of MK-7 daily are typical for bone and cardiovascular support.
References by claim
vitamin k deficiency / clotting cofactor support
Track Vitamin K (menaquinone) with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.