Vitamin D2 vs D3: What Your Label Should Say

D2 and D3 Are Not the Same

Vitamin D comes in two forms: D2 (ergocalciferol) and D3 (cholecalciferol). A 2011 study by Heaney et al., published in The Journal of Clinical Endocrinology & Metabolism, found that D3 is approximately 87% more potent than D2 at raising and maintaining serum 25(OH)D levels — the standard measure of vitamin D status in the body.

Yet many supplement labels simply list "Vitamin D" without specifying the form.

Why the Form Matters

The difference between D2 and D3 isn't subtle. If your label says "Vitamin D 1000 IU" without specifying D2 or D3, you have no way to know what you're getting. And if it's D2, you may need a significantly higher dose to achieve the same blood levels as D3.

It's worth noting that "more potent at raising blood levels" doesn't automatically mean D3 is better for every clinical outcome — but for most people trying to maintain healthy vitamin D status, D3 is the more efficient choice.

What to Look For on the Label

A transparent vitamin D label should show:

• The specific form — "Vitamin D3 (as cholecalciferol)" is what you want to see

• The dose in IU or mcg — clearly stated per serving

• The source — D3 is typically from lanolin (sheep's wool) or lichen (vegan). D2 is from irradiated mushrooms or fungi.

How We Score Vitamin D Products

Our SupplementScore algorithm checks whether vitamin D products disclose the specific form (D2 vs D3). Products that clearly state the form score higher on Label Transparency. Products that list only "Vitamin D" without specifying the form lose points.

We analyzed thousands of vitamin D products in our database. See how they rank.

The Bottom Line

Look for Vitamin D3 (cholecalciferol) on the label. If a product just says "Vitamin D" without specifying the form — that's a transparency issue. You deserve to know what you're paying for.