Vitamin D3 + K2
D3/K2 · Cholecalciferol + MK-7 · D3 K2
Vitamin D3 (cholecalciferol) is a fat-soluble secosteroid hormone precursor essential for calcium homeostasis, immune function, and hundreds of downstream gene-regulatory effects. Vitamin K2 (menaquinone, specifically MK-7 and MK-4 forms) is a fat-soluble cofactor essential for activating matrix Gla protein (MGP) and osteocalcin - proteins that direct calcium INTO bone and AWAY from arterial walls. The two vitamins are almost always co-supplemented because D3 increases calcium absorption and K2 determines where that calcium deposits.
Starting dose. D3: 5,000 IU + K2 (MK-7) 100-200 mcg daily
Take with a fat-containing meal (fat-soluble vitamins require fat for absorption). Test 25(OH)D after 8-12 weeks to titrate dose. Typical target: 40-60 ng/mL.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
Vitamin D3 is hydroxylated in the liver to 25-hydroxyvitamin D (calcidiol, the storage form measured in blood tests) and then in the kidneys and peripheral tissues to 1,25-dihydroxyvitamin D (calcitriol, the active hormone). Calcitriol binds the vitamin D receptor (VDR), a nuclear receptor expressed in virtually every tissue, and regulates transcription of >1,000 genes involved in calcium homeostasis, cell growth/differentiation, immune function, and antimicrobial peptide production (cathelicidin).
Vitamin K2 activates vitamin K-dependent proteins via gamma-carboxylation of glutamate residues. The key K2-dependent proteins are: (1) osteocalcin - binds calcium and incorporates it into bone hydroxyapatite, (2) matrix Gla protein (MGP) - prevents calcium deposition in arteries and soft tissues, (3) Gas6 - supports cell survival and phagocytosis. Without K2, these proteins circulate in inactive (uncarboxylated) form and calcium can deposit in inappropriate locations.
The D3+K2 synergy is mechanistic: D3 increases calcium absorption from the gut and mobilization from bone. K2 then directs that calcium into bone (via osteocalcin activation) and prevents arterial deposition (via MGP activation). The Rotterdam Study demonstrated this: high K2 intake was associated with 50% lower cardiovascular mortality and 57% lower arterial calcification.
What to expect
Weeks 1-4: Blood levels rising but subjective effects minimal. Test 25(OH)D after 8 weeks.
Evidence
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.
Exact-molecule abstract evidence. ESearch was run and 5 source-candidate PMIDs were EFetch-checked; no usable exact-molecule abstract sentence was found.
Dose/route: D3: 5,000 IU + K2 (MK-7) 100-200 mcg daily; Oral; Once daily with fattiest meal of day. No selected live abstract sentence verified this complete regimen.
Mechanism as written in source JSON. No selected live abstract sentence verified the complete mechanism at the card formulation/route and relevant population/model.
Primary safety claim as written in source JSON. No selected live abstract sentence verified the complete safety claim for this exact formulation and route.
Interactions & stacking
Two different questions: what is documented about running these together, and what is documented about drawing them into the same syringe. A good pharmacological partner can still have to be pinned separately.
Documented together
Keep separate
Check any specific pair in the Stack & Interaction Checker, which answers both questions separately. Absence of a documented conflict is not evidence of safety.
Pharmacokinetics
Vitamin D3: ~2-3 weeks (25(OH)D form). K2 MK-7: ~72 hours. K2 MK-4: ~1-2 hours.
D3: ~7 days to peak serum 25(OH)D. K2 MK-7: ~4-6 hours. K2 MK-4: ~1-2 hours.
D3: 8-12 weeks to steady state after dose change. K2 MK-7: stable steady state within 2-3 weeks.
Both fat-soluble - absorption requires dietary fat. D3 absorption ~50-80% with fatty meal, <20% on empty stomach. K2 MK-7 absorption ~40-80% with fat.
D3 effects persist weeks after last dose due to long half-life and tissue storage. K2 MK-7 daily dosing maintains stable activated MGP/osteocalcin levels.
D3: hepatic hydroxylation to 25(OH)D, then renal/peripheral tissue to 1,25(OH)2D. Biliary excretion of metabolites. K2: hepatic uptake, biliary excretion.
Storage. Store at room temperature (20-25C) in a cool, dry place. Protect from light. Capsules/softgels shelf-stable 2+ years. Liquid D3 drops stable when capped tightly. Both D3 and K2 are fat-soluble and stable in oil carriers.
Regulatory status
Classified as dietary supplements in the US - no prescription required for typical doses. Vitamin D is available as prescription at 50,000 IU (ergocalciferol D2 or cholecalciferol D3) for deficiency correction. K2 has no prescription equivalent.
Put it to work
Calculate, log & track
Open Vitamin D3 + K2 straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
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The guide & community
The complete Vitamin D3 + K2 walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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