Within the K2 family, two menaquinones dominate the supplement market — and they could hardly be more pharmacokinetically different. MK-4, the short-chain form (used in milligram doses in Japanese osteoporosis medicine), and MK-7, the long-chain form produced by bacterial fermentation. Choosing between them is not a matter of taste: a single number — serum half-life — dictates the entire dosing architecture.
The half-life gulf
The decisive head-to-head data come from Sato and colleagues (Nutr J, 2012), who measured serum responses to single equal doses of MK-4 and MK-7 in healthy women. The result was stark: MK-4 produced no measurable rise in serum menaquinone levels at nutritional doses — it is absorbed but cleared within 1–2 hours, vanishing into tissues and metabolism before a serum plateau can form. MK-7 rose reliably and stayed: its serum half-life runs around three days, thanks to redistribution into LDL particles that circulate lazily through the bloodstream, dropping vitamin K at extrahepatic tissues — bone and vessel wall — with each pass (the delivery logic our K2 vs K1 article details). Half-life arithmetic does the rest. A compound cleared in hours must be re-dosed repeatedly and heavily to maintain exposure — hence MK-4’s pharmaceutical regimen of 15 mg three times daily, a 45,000 µg daily load. A compound with a 3-day half-life accumulates: daily dosing stacks onto yesterday’s remainder, building to a stable plateau roughly 4–5× the single-dose level within two weeks. That is how 90–200 µg of MK-7 once daily — a few hundred times less material — sustains continuous vitamin K delivery that MK-4’s spikes never achieve.
What the plateau does: the MK-7 trials
Steady-state exposure is not an abstraction; it is what the long-term randomised trials were built on. In the three-year, placebo-controlled trial of 180 µg MK-7 daily in 244 postmenopausal women, Knapen and colleagues (Osteoporos Int, 2013) found significantly reduced age-related decline in bone mineral content and density at the lumbar spine and femoral neck, with improved bone strength indices — alongside the biochemical confirmation that circulating uncarboxylated osteocalcin fell, proving the target proteins were being switched on. The companion vascular analysis (Knapen, Thromb Haemost 2015) reported significantly improved arterial stiffness parameters (carotid-femoral pulse wave velocity and stiffness index) versus placebo over the same three years — most markedly in women who started with high uncarboxylated MGP, i.e., the most vitamin-K-underserved vessels. Three-year outcomes, physiological endpoints, microgram doses: the entire evidence package presupposes the stable serum plateau only MK-7 provides.
What this means for a daily-drop format
The plateau logic has practical corollaries worth spelling out. Forgiveness: with a 3-day half-life, a missed day dents the plateau by a fraction rather than resetting it — the pharmacology tolerates real life. Timing freedom: once daily, any consistent time, with a fat-containing meal (menaquinones are fat-soluble; the oil-drop format carries its own vehicle). Dose honesty: a 100 µg all-trans MK-7 drop sits squarely in the trial-tested range — there is no evidence-based case for milligram MK-7 dosing, and the all-trans qualifier matters enough to have its own article. And the standing rule remains: anticoagulated patients read the warfarin interaction rules first — a long half-life makes consistency even more important, in both directions.
The clinical bottom line
MK-4 disappears from serum in hours and therefore lives in pharmaceutical milligram regimens; MK-7 circulates for days, accumulates to a stable plateau on once-daily microgram dosing, and is the form behind the three-year bone and arterial-stiffness trials. In K2 supplementation, half-life is not a detail — it is the dose, the schedule and the evidence base, all in one number.
Primary sources
- Sato T, Schurgers LJ, Uenishi K. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J. 2012;11:93. doi:10.1186/1475-2891-11-93
- Knapen MH, Drummen NE, Smit E, Vermeer C, Theuwissen E. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013;24(9):2499–2507. doi:10.1007/s00198-013-2325-6
- Knapen MH, Braam LA, Drummen NE, Bekers O, Hoeks AP, Vermeer C. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women: a double-blind randomised clinical trial. Thromb Haemost. 2015;113(5):1135–1144. doi:10.1160/TH14-08-0675
- Schurgers LJ, Teunissen KJ, Hamulyák K, et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2007;109(8):3279–3283. doi:10.1182/blood-2006-08-040709
- Halder M, et al. Vitamin K: double bonds beyond coagulation — insights into differences between vitamin K1 and K2 in health and disease. Int J Mol Sci. 2019;20(4):896. doi:10.3390/ijms20040896
Educational information, not medical advice. Anticoagulated patients: physician first, always.
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