Vitamins
Vitamin D3 + K2
Vitamin D deficiency is widespread globally and linked to reduced testosterone, immune dysfunction, and bone weakness. D3 + K2 is the standard stack.
Effective Dose
2000–4000 IU D3 + 100µg K2 / day
per clinical evidence
Evidence Level
Strong
Vitamins
Mechanism
Nuclear receptor activation
primary action
Best For
Deficiency correction
Immunity, Bone density
This profile is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications.
What Is Vitamin D3 + K2?
Vitamin D3 (cholecalciferol) is synthesised in skin upon UVB exposure and acts as a prohormone — converted to its active form 1,25-dihydroxyvitamin D3 (calcitriol) in the kidneys. It regulates over 1000 genes. K2 (MK-7 form) directs calcium into bones and away from arterial walls, making it an important co-factor for long-term D3 supplementation.
How It Works: The Science
Calcitriol binds the vitamin D receptor (VDR), a nuclear receptor found in nearly every tissue. VDR activation regulates calcium absorption in the gut, bone mineralisation, immune cell differentiation, and testosterone-related gene expression in Leydig cells. K2 activates osteocalcin (bone matrix formation) and matrix Gla protein (arterial calcium removal).
Primary Mechanism
Nuclear receptor activation
Evidence-Based Benefits
Dosage Guide
Effective Dose
2000–4000 IU D3 + 100µg K2 / day
2000–4000 IU D3 daily for maintenance in adults with average sun exposure. Higher doses (5000+ IU) require periodic 25(OH)D blood testing. Take with K2 MK-7 (100–200µg) and a fat-containing meal — vitamin D is fat-soluble.
Safety Profile & Side Effects
Vitamin D toxicity (hypercalcaemia) occurs at sustained doses >10,000 IU/day over months — not achievable at standard supplement doses. K2 MK-7 has no established toxicity at supplemental doses. Blood testing to confirm levels before and during supplementation is best practice.
Who Should (and Shouldn't) Take It
Virtually everyone in temperate climates, those with desk jobs (limited sun exposure), and anyone with known deficiency (serum 25(OH)D <50 nmol/L). Athletes training indoors year-round should consider year-round supplementation.
Frequently Asked Questions
Related Ingredients
Medical Disclaimer
Ingredient profiles are for informational purposes only and do not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications. Full disclaimer →