Ultra K2 Menaquinone - 4 15000 mcg by Klaire Labs/SFI Health

If your DEXA scan shows low bone density or you’re postmenopausal and working on bone health, high-dose vitamin K2 MK-4 is one of the few supplements with randomized trials behind it. It’s also reasonable for long-term steroid users and those already on osteoporosis medications who want an adjunct. If your calcium score is a concern, K2 is being studied for vascular calcification, but effects are modest and slower to show. Check Vitamin D, 25-Hydroxy first; K2 works best alongside adequate vitamin D.

MK-4 activates “Gla” proteins by carboxylation, an on-switch that lets them bind calcium. In bone, that’s osteocalcin (the protein that helps lock calcium into the matrix). In arteries, it’s matrix Gla protein, which inhibits calcium deposition in vessel walls. This 15 mg MK-4 is a pharmacologic dose; Japanese trials using 45 mg/day (split doses) reported fewer fractures. Compared with MK-7, MK-4 has a shorter half-life but the best fracture data at higher doses.

Take 1 capsule with food one to three times daily, matching the manufacturer’s guidance and the short half-life of MK-4. Many clinicians target 45 mg/day in divided doses when aiming for bone outcomes; 15 mg/day is a lower, maintenance-like approach. Pair with vitamin D3 and adequate dietary calcium if your intake is low. Expect bone turnover markers (like Osteocalcin) to shift within 4 to 12 weeks, while bone density changes take months to years.

Do not use vitamin K2 if you take warfarin (Coumadin); it counteracts its effect, altering Prothrombin Time/INR (the blood-thinning measure). Direct oral anticoagulants like apixaban and rivaroxaban don’t rely on vitamin K, but discuss any high-dose K2 with your prescriber. Large doses of vitamin E can blunt vitamin K activity. Pregnancy and dialysis patients should only use high-dose MK-4 with clinician oversight.