Calcium Partitioning
Vitamin D + Vitamin K2
Vitamin D raises calcium absorption; K2 directs that calcium to bones instead of arteries. Together they cover the partitioning problem.
Vitamin
Vitamin D is a fat-soluble hormone and micronutrient essential for calcium absorption, bone health, immune function, and cellular regulation. Most people have insufficient levels and may benefit from supplementation, particularly those with limited sun exposure.
Full Vitamin D profile →Vitamin
Vitamin K2 (MK-7) is a long-chain menaquinone that activates bone and vascular proteins involved in calcium regulation, supporting bone mineralization and cardiovascular health. MK-7 from plant sources like chickpea offers improved bioavailability and longer tissue half-life compared to K1.
Full Vitamin K2 profile →Why they work together
Vitamin D increases intestinal calcium absorption — effective, but without a partitioning signal, some of that extra calcium ends up deposited in arterial walls rather than bone. Vitamin K2 (specifically MK-7) activates matrix Gla protein in arteries to inhibit calcification, and activates osteocalcin in bone to direct calcium deposition there. Taking D3 without K2 at higher doses (2,000+ IU daily) raises a theoretical concern about arterial calcification. Pairing them eliminates that concern and is the canonical longevity-stack combination.
How to dose them
1,000–2,000 IU vitamin D3 + 90–180 mcg MK-7 daily, with a fat-containing meal (both are fat-soluble). Many products now combine them in one softgel. Higher D3 doses (5,000 IU) merit higher K2 (180 mcg) for partitioning balance.
Evidence
Combination logic is well-established mechanistically; Knapen 2017 (PMID: 29405321) showed K2 reduces arterial stiffness in combination protocols. Still short on large-scale cardiovascular outcome trials of the combination, but the supplement-community consensus is strong.
Watch-outs
If you take warfarin, K2 supplementation interferes meaningfully with INR — work with prescriber before adding. K2 at supplement doses has no other significant drug interactions. D3 at very high chronic doses (>5,000 IU without blood monitoring) can cause hypercalcemia regardless of K2 pairing.
Next steps
Educational only. Synergy pairs are not prescriptions. Run any new supplement combination past your clinician if you take prescription medication.