Vitamin D, K2 and magnesium

Dr. James Dinicolantonio SUBSTACK Jan.23rd, 2026

VITAMIN D Does NOT Work WITHOUT MAGNESIUM and VITAMIN K2

If you’re taking vitamin D3 without magnesium and vitamin K2 you’re not getting the full benefits and in some cases you could even be increasing risk. Here’s how the system actually works:

1. Vitamin D3 — Calcium Absorption

Vitamin D3 helps your body absorb calcium from food and supplements.

Without enough D3, calcium absorption is poor.

2. Vitamin K2 — Calcium Direction

Vitamin K2 tells calcium where to go:

✔ Into bones and teeth

❌ Not into arteries or soft tissues

Without K2, absorbed calcium can accumulate in blood vessels, contributing to arterial calcification.

3. Magnesium — Vitamin D Activation

Magnesium is required to activate vitamin D.

It converts vitamin D into the active hormone 1,25-dihydroxycholecalciferol (calcitriol).

Around ~50% of people are magnesium deficient, which can silently block vitamin D from working.

Why This Matters

Taking vitamin D alone can:

- Increase calcium absorption without proper regulation (arterial calcifications)

- Stress magnesium stores

- Reduce the effectiveness of vitamin D over time

The Takeaway

Vitamin D + K2 + Magnesium = a functional system

Together, they support:

- Strong bones and teeth

- Healthy arteries

- Better sleep and stress resilience

- Proper calcium metabolism

- Overall metabolic and cardiovascular health