Q
D2 or D3 — which Vitamin D supplement is better?
⚡ Quick answer
D3 (cholecalciferol) — significantly more effective than D2.
Vitamin D3 (cholecalciferol) is significantly more effective than D2 (ergocalciferol). Studies show D3 raises blood levels 56-87% more than equivalent doses of D2.
Why: D3 is the form your skin makes from sunlight and is more readily used by the body. D2 comes from plants and yeast, requires more conversion steps, and is less stable.
What to buy:
- Form: D3 (cholecalciferol)
- Dose: 1000-2000 IU daily for maintenance, 4000-5000 IU if deficient
- Co-factor: pair with Vitamin K2 (100mcg MK-7 form) — they work together
- Take with: fat-containing meal — Vitamin D is fat-soluble
Who needs supplementation: most people, especially in winter, those who work indoors, dark-skinned people in northern latitudes, and elderly. Sun is the best source but inadequate for many.
Get tested: 25-OH Vitamin D blood test. Aim for 40-60 ng/mL (100-150 nmol/L). Below 30 = deficient.
Watch out: high-dose Vitamin D (10,000+ IU daily) can cause toxicity. Always test before mega-dosing.
Read our full evidence-based guide on deficiencies for the complete picture.
View Full Guide →We write from peer-reviewed research and clinical guidance. These links let you read the underlying evidence yourself rather than taking our word for it.