Vitamin D2 vs D3: Which Form Is More Effective?

Comparison Guide · Updated 2025

Vitamin D2 vs D3: The Evidence Is Clear

Vitamin D exists in two supplemental forms: D2 (ergocalciferol, from yeast/fungi) and D3 (cholecalciferol, from animal sources or lichen). The difference in efficacy is substantial and well-established.

Why D3 Wins — The Pharmacokinetics

Multiple head-to-head RCTs confirm: at the same dose, D3 raises serum 25(OH)D levels 2–3x more than D2 and maintains those levels significantly longer. A landmark 2011 study by Tripkovic et al. found D3 supplementation was 87% more potent than D2 at raising and maintaining serum vitamin D levels over 12 weeks.

The mechanism: D3 converts to 25(OH)D3 more efficiently than D2 converts to 25(OH)D2, and 25(OH)D3 has a longer half-life in the body (2–3 weeks vs 1–2 weeks for D2). This means D3 maintains stable blood levels with less frequent dosing, while D2 fluctuates more rapidly.

D2 Sources: Where You Encounter It

D2 appears in fortified foods (many plant milks, cereals), mushrooms exposed to UV light, and in many prescription-strength vitamin D supplements (50,000 IU D2 is commonly prescribed). Some multivitamins still use D2 for cost reasons. Ergocalciferol (D2) is vegan-compatible, which is why it’s common in plant-based products.

Vegan D3 — The Solution

Historically, D3 came exclusively from animal sources (lanolin from sheep’s wool or fish liver oil). Vegan D3 from lichen is now widely available and provides identical efficacy to animal-derived D3. Vitashine and Zooki produce well-validated lichen-derived D3. Vegans should specifically seek out lichen-based D3, not settle for D2.

The D3 + K2 Combination

At doses above 2,000 IU/day, D3 raises calcium absorption. Vitamin K2 (MK-7 form, 100–200mcg) directs that calcium to bones rather than arteries. This combination is consistently recommended for anyone supplementing D3 at meaningful doses. K2 MK-7 from fermented natto is vegan; MK-4 is synthetic and also vegan. MK-7 has a longer half-life and is preferred.

Verdict

Always choose D3 over D2. D3 raises blood levels 2–3x more efficiently and maintains them longer. Vegans: use lichen-derived D3, not D2. If you’ve been prescribed high-dose D2 by a doctor, ask about switching to D3 — the same therapeutic effect is achieved at lower doses. Standard supplementation dose for most adults: 2,000–4,000 IU D3 daily.

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Vitamin D3 vs D2: Which Is More Effective? Vitamin D3 vs D2: why D3 is 87% more potent (longer half-life, better binding protein affinity), why D2 is still prescribed, and vegan D3 (lichen) as the solution.

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