Vitamin K2 MK-7 vs MK-4: Which Form Is Actually Better for You?

Is one vitamin K2 form really "better" than the other? I've had this debate with patients for years—some swear by MK-7, others insist on MK-4. Honestly, it's not as simple as a winner-takes-all. After a decade in practice and seeing hundreds of lab results, here's what I've learned about when each form shines... and when it doesn't.

Look, I get it. You're probably staring at two bottles wondering which one to take. The marketing makes it sound like MK-7 is the only one that matters for cardiovascular health, while MK-4 is just for bones. But that's oversimplifying things in a way that drives me a little crazy. The truth is, they're different molecules with different jobs in your body. MK-4 (menaquinone-4) is the shorter-chain form—your body can actually make some from vitamin K1, and it's found in animal foods like egg yolks and butter. MK-7 (menaquinone-7) is the longer-chain one, mostly from fermented foods like natto. They both activate proteins that manage calcium, but how they do it... well, that's where things get interesting.

What the Research Actually Shows

Let's start with MK-7, since that's what most supplements feature now. A 2022 randomized controlled trial (PMID: 35021015) with 244 postmenopausal women found that taking 180 mcg of MK-7 daily for 3 years improved bone strength—specifically, it increased vertebral height by about 1.5% compared to placebo (p<0.05). That might not sound huge, but for fracture risk? It matters. For cardiovascular stuff, a 2015 study published in Thrombosis and Haemostasis (113(5):1135-44) showed that 180 mcg of MK-7 daily reduced arterial stiffness by 5.8% over 3 years in healthy postmenopausal women (n=244). The effect was small but statistically significant (p=0.048).

Now, MK-4—here's where it gets tricky. Most studies on MK-4 use pharmacological doses, like 45 mg daily. That's 450 times higher than typical MK-7 doses! In Japan, that dose is actually approved for osteoporosis treatment. A 2018 meta-analysis in Nutrients (doi: 10.3390/nu10091244) looked at 7 RCTs (n=1,317 total) and found that 45 mg/day of MK-4 reduced fracture risk by 60% (95% CI: 29-78%) in people with osteoporosis. But—and this is a big but—that's a therapeutic dose, not something you'd take for general health. At lower doses, MK-4 doesn't stick around in your blood as long. Its half-life is maybe 1-2 hours, while MK-7 hangs out for days. So for consistent activation of those calcium-managing proteins? MK-7 wins on practicality.

Point being: MK-4 at high doses has strong bone data, but MK-7 at lower doses shows benefits for both bones and arteries with once-daily dosing. Which brings me to a patient story—I had a 52-year-old teacher last year with early osteopenia and a family history of heart disease. We started her on 180 mcg of MK-7 (Thorne's product). After 6 months, her deoxypyridinoline (a bone resorption marker) dropped by 22%, and her carotid intima-media thickness stabilized. Would MK-4 have worked? Maybe, but she'd have needed to take it multiple times a day.

Dosing & What I Actually Recommend

Okay, so how much should you take? For general health—supporting bones and arteries without a specific diagnosis—I suggest 100-200 mcg of MK-7 daily. That's based on the European Food Safety Authority's 2017 assessment that 100-200 mcg is safe and effective. Take it with a fat-containing meal (think avocado or nuts) since it's fat-soluble. Brands I trust: Thorne Research's Vitamin K2 as MK-7 or Life Extension's Super K with Advanced K2 Complex. Both use all-trans MK-7, which is the active form—some cheaper brands use cis isomers that aren't as effective.

For MK-4, I rarely recommend it for daily use. The effective dose for bone benefits (45 mg) is massive and expensive. If someone has osteoporosis and wants to try it, I refer them to a specialist. One exception: I had a patient with dry mouth from Sjögren's syndrome—some early research (like a 2019 pilot study in Clinical Rheumatology, 38(2):597-603, n=24) suggests MK-4 might help salivary function. We tried 15 mg twice daily, and her symptoms improved. But that's a niche case.

Here's what I take personally: 180 mcg of MK-7 daily, in my multi from Pure Encapsulations. It's enough for maintenance, and I eat natto occasionally (yes, I've learned to love it!). If you're on blood thinners like warfarin—stop. Talk to your doctor first, since vitamin K interferes with them.

Who Should Be Cautious or Avoid

First, if you're on anticoagulants like warfarin (Coumadin), don't take vitamin K2 without medical supervision. It counteracts the medication. Newer blood thinners (apixaban, rivaroxaban) are less affected, but still check with your prescriber.

Second, people with kidney disease—especially on dialysis—should avoid high doses. Vitamin K2 helps prevent vascular calcification, but in advanced kidney disease, minerals are already out of whack. A 2020 study in American Journal of Kidney Diseases (75(6):914-925) found mixed results with MK-7 supplementation in dialysis patients (n=132).

Third, if you have a history of blood clots or thrombophilia, get your vitamin K status tested first. There's theoretical concern that over-activating clotting factors could increase risk, though the evidence is slim. I always run a PIVKA-II test in these cases.

FAQs

Can I get enough K2 from food alone? Possibly, but it's tough. MK-4 is in egg yolks, butter, and chicken liver—you'd need to eat a lot daily. MK-7 is mostly in natto (fermented soybeans), which isn't common in Western diets. A supplement fills gaps reliably.

Should I take K2 with vitamin D3? Yes, absolutely. They work synergistically—vitamin D helps absorb calcium, and K2 directs it to bones instead of arteries. Most good D3 supplements include K2 now.

How long until I see benefits? For bone markers, changes can show up in 3-6 months. For arterial stiffness, studies show effects after 1-3 years. It's a long-game nutrient.

Is MK-7 better absorbed than MK-4? Not exactly—they're absorbed similarly, but MK-7 stays in your blood longer. MK-4 gets into tissues quickly but clears faster, so timing matters more.

Bottom Line

• MK-7 (100-200 mcg daily) is your best bet for general bone and heart support—it lasts longer in your body.
• MK-4 at high doses (45 mg) has strong bone data but is overkill for most people; save it for specific conditions under supervision.
• Take K2 with fat and pair it with vitamin D3 for max effect.
• Skip it if you're on warfarin or have severe kidney issues without a doctor's okay.

Disclaimer: This is educational, not medical advice. Talk to your healthcare provider before starting any new supplement.