Vitamin D3 vs D2: Cholecalciferol vs Ergocalciferol

Vitamin D supplements come in two main forms: D3 (cholecalciferol; the form made in the skin by sunlight and found in animal foods) and D2 (ergocalciferol; the form found mainly in mushrooms). The “D3” and “D2” on the label are often turned into the question “which is better.” This page sets side by side the difference between the two forms in raising blood levels, under what conditions this difference was seen and what it did not measure, the preference of the Türkiye consensus, and product status. ^[1] For vitamin D as a whole, see: Vitamin D.

Differences between D3 and D2

The “evidence grade” row in the table points to the area-based grades in the vitamin D guide: rickets and osteomalacia in marked deficiency A, fracture prevention and fall prevention in the general population E, respiratory tract infections C, cancer and cardiovascular events E. None of the grades was calculated for the D2–D3 difference.

What the evidence says: blood level

The systematic review by Tripkovic and colleagues searched for randomized trials directly comparing D3 with D2 in adults; 7 of 10 possible trials entered the meta-analysis. The meta-analysis showed that D3 supplementation raised serum 25(OH)D significantly more than D2 (P = 0.001). By dosing frequency, the D3 advantage was significant in trials giving a single high dose (bolus) (3 trials with data, P = 0.0002); with daily use this effect disappeared. In the main analysis, heterogeneity between studies was high (I² 81%). ^[2] The authors write that D3 may be the preferred form, but that metabolic pathways and the effects of age, sex and ethnicity need additional research. ^[2]

The limit of this finding is clear: the measured outcome is serum 25(OH)D level; it is not fracture, falls or any other clinical outcome. The NIH also states that both raise blood levels and appear equivalent in healing rickets; the result that “D3 raises more” does not mean that a particular product is mandatory for every person. ^[1]

Why do daily and single high doses matter?

Knowing where the difference appears is more instructive than individual products. In the Tripkovic meta-analysis, the D3 advantage was marked in bolus regimens; with daily use the difference between D2 and D3 disappeared. ^[2] The Türkiye consensus likewise states that daily cholecalciferol is the form that best mimics continuous endogenous production, and that although seasonal or yearly single doses of 300,000–600,000 IU seem more practical, they raise serious safety concern because of increased risk of falls and fractures, particularly in older adults. ^[3] This page does not define any regimen or amount; decisions about loading belong to the physician.

Mushroom D2 and food sources

Animal foods contain mainly D3, and mushrooms mainly D2. According to the review by Cardwell and colleagues, the most common form in mushrooms is D2, with less D3 and D4. A mushroom exposed to UV light can form a nutritionally significant amount of vitamin D; according to the review, D2 levels in UV-treated mushrooms can fall with storage and cooking, but when consumed before the expiry date they remain above 10 µg per 100 grams. ^[4] This is a review finding; the actual amount in a store-bought product is learned from the label. The D2–D3 findings for supplements do not directly measure the value of D2 obtained from food.

Forms, status and labels in Türkiye

According to the 2026 Türkiye expert consensus, oral vitamin D preparations in the country come as capsules, drops and tablets; there is also an intramuscular ampoule preparation. The consensus states similar efficacy between drops, capsules and tablets at equivalent amounts and recommends cholecalciferol (D3) for supplementation and treatment. ^[3] The form name alone does not describe the amount or use: capsule and tablet strengths span a wide range, and the concentration of drops varies by product.

There are two different frameworks in Türkiye. The health claim page of the TİTCK (Turkish Medicines and Medical Devices Agency) defines a drug (human medicinal product) as a substance presented as having properties that treat or prevent disease in humans, or used to correct physiological functions or for medical diagnosis. ^[5] The Communiqué on Food Supplements (Takviye Edici Gıdalar Tebliği, 2013/49), published in the Official Gazette on August 16, 2013, requires statements on the supplement label such as “Do not exceed the recommended daily portion” (Tavsiye edilen günlük porsiyonu aşmayın), “Food supplements cannot replace a normal diet” (Takviye edici gıdalar normal beslenmenin yerine geçemez) and “Not a drug. Not used for prevention or treatment of diseases” (İlaç değildir. Hastalıkların önlenmesi veya tedavi edilmesi amacıyla kullanılmaz). ^[6] A D2 or D3 label does not determine whether the product is a drug or a supplement; this is read from the product’s own label.

Other forms and reading the label

The NIH reports that calcifediol (25(OH)D) is three to five times as potent as D3 per equal microgram; the Türkiye consensus says that hydroxylated forms may be considered in conditions such as malabsorption. These are products determined by the physician. ^{[1] [3]} Three separate pieces of information are read on the label: form (D2 or D3), unit (IU or µg; 1 µg = 40 IU ^[1]) and serving (one drop, one capsule, one mL). The upper limit the NIH gives for vitamin D is 4,000 IU/day (100 µg) in adults; additional components in combination products are evaluated separately. ^[1] For products sold with D3 and K2 together, warfarin interaction and the limits of evidence are in a separate guide.

Verdict

The evidence says this: D3 has raised serum 25(OH)D levels in adults more than D2; this advantage was seen in single high-dose regimens and disappeared with daily use. The two forms appear equivalent in healing rickets; whether the D2–D3 difference translates into fracture, falls or any other clinical outcome was not measured in this meta-analysis. The Türkiye expert consensus recommends cholecalciferol (D3). A price difference does not show a proven clinical difference; the real comparison is made on the unit and serving on the label. This page does not recommend a personal amount or product.