Vitamin D2 (Ergocalciferol)
Also known as: ergocalciferol, calciferol, vitamin D2, viosterol
Ergocalciferol is the plant and fungal form of vitamin D, produced by UV irradiation of ergosterol from yeast or mushrooms. It has long been the vegan-friendly option and is still used in fortified foods and some supplements. It raises serum 25(OH)D, but NIH ODS notes that D3 raises it further and sustains it longer, a finding backed by meta-analyses, so D2 is mostly chosen for cost, heritage formulas, or vegan positioning where lichen D3 is not available.
Research summary
Hydroxylated in the liver to 25(OH)D2 and in the kidney to the active hormone, acting on the vitamin D receptor like D3 but with a shorter-lived rise in circulating 25(OH)D.
Dosage
Daily amounts, of compound.
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 400 IU | 400–2,000 IU | 4,000 IU | 4,000 IU |
NIH ODS — UL is 100 mcg (4,000 IU) per day for adults, applying to vitamin D from all forms
Same RDA and UL as D3: 600 IU (15 mcg) adults, 800 IU (20 mcg) over 70, UL 4,000 IU (100 mcg); 40 IU = 1 mcg. Because D2 is less efficient at raising 25(OH)D per IU, formulators often specify D3 when the goal is a measurable rise in status; if D2 is used, do not assume IU-for-IU equivalence. Take with dietary fat. High-dose prescription ergocalciferol (50,000 IU weekly) is a drug regimen and outside supplement dosing.
Source material: UV-irradiated ergosterol from yeast
As supplied: Typically supplied as a 100,000 IU/g powder dilution on a carrier, like D3; 2,000 IU ≈ 20 mg of powder
Forms of Vitamin D
| Form | Typical dose | Element % | Formats | Price |
|---|---|---|---|---|
| Vitamin D2 (Ergocalciferol) | 400–2,000 IU | — | Capsule, Powder, Tablet, Softgel, Gummy, Liquid | low |
| Vitamin D3 (Cholecalciferol) | 1,000–2,000 IU | — | Capsule, Powder, Tablet, Softgel, Gummy, Liquid | low |
| Vitamin D3 (Vegan, Lichen-Sourced) | 1,000–2,000 IU | — | Capsule, Powder, Tablet, Softgel, Gummy, Liquid | mid |
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Less stable than D3 in some matrices; check overage requirements with the supplier.
Formulation notes
Counts toward the shared vitamin D UL alongside any D3 in the formula.
- Has an upper limit
Sources
- Vitamin D — Health Professional Fact SheetNIH ODS
- Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. (Tripkovic L, 2012)PubMed
- Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation on Serum 25-Hydroxyvitamin D Concentration (Total 25(OH)D, 25(OH)D2, and 25(OH)D3) and Importance of Body Mass Index: A Systematic Review and Meta-Analysis. (van den Heuvel EG, 2024)PubMed
Related ingredients
Vitamin D3 (Cholecalciferol)
VitaminThe form of vitamin D the body makes from sunlight and the most effective supplemental form for raising blood levels.
Typical: 1,000–2,000 IU
Vitamin D3 (Vegan, Lichen-Sourced)
VitaminChemically identical cholecalciferol extracted from lichen rather than sheep's wool lanolin, which lets a product carry vegan and vegetarian claims while keeping the D3 form that raises and holds serum 25(OH)D better than D2.
Typical: 1,000–2,000 IU
Cod Liver Oil
Fatty acidCod liver oil is pressed from the livers of Atlantic cod.
Typical: 1,000–2,000 mg
Vitamin C (Ascorbic Acid)
VitaminAscorbic acid is the reference form of vitamin C and the most common form in supplements; NIH ODS notes its bioavailability equals that of vitamin C naturally present in food.
Typical: 250–1,000 mg
Probiotic Blend (Multi-Strain)
ProbioticA generic placeholder for a multi-strain probiotic blend, typically combining several Lactobacillus and Bifidobacterium species and sometimes Streptococcus thermophilus or a Bacillus spore.
Typical: 10–50 B CFU