NOW Foods Vitamin K-2 100 mcg provides menaquinone-7 (MK-7) — the longest-acting and most bioavailable form of vitamin K2 — derived from natto fermentation. K2 MK-7 has a half-life of approximately 72 hours (versus a few hours for K1), maintaining active serum levels throughout the day from a single daily dose. Vitamin K2 is the biological traffic director for calcium — activating osteocalcin to incorporate calcium into bone matrix while simultaneously activating matrix Gla protein (MGP) to prevent calcium from depositing in arterial walls. This makes K2 an essential partner to vitamin D3 and calcium supplementation, ensuring calcium goes where it belongs. NOW Foods uses 100 mcg of MK-7 per capsule — within the clinically studied range — manufactured in their GMP-certified facility with potency verification on each batch.