Moderate evidenceVitamins & minerals

Vitamin D2 (Ergocalciferol)

Ergocalciferol does raise 25-hydroxyvitamin D — just roughly half as efficiently per IU as D3, with a shorter-lived effect. It is a legitimate plant-derived option, but lichen-derived vegan D3 now exists and is the better default for almost everyone.

What the science says

D3 raises 25(OH)D more effectively than D2 Strong evidence
A meta-analysis of 10 RCTs found D3 significantly more effective than D2 at raising total 25(OH)D, with the gap widest for bolus dosing. A 12-week randomised food-fortification trial gave 15 µg/day (600 IU) of D2 or D3 to South Asian and white European women through the winter: D3 raised 25(OH)D roughly twice as much as D2 at the identical dose. The mechanism is faster clearance and lower binding affinity of D2 metabolites for vitamin D binding protein.
D2 still corrects deficiency Moderate evidence
It does. The standard US prescription for deficiency remains 50,000 IU ergocalciferol weekly for 8–12 weeks, and it works. The practical problems are potency per IU and the faster decline between doses, which makes intermittent high-dose D2 regimens leave larger troughs than equivalent D3 schedules.
D2 can lower your measured vitamin D level Moderate evidence
Supplementing with D2 suppresses circulating 25(OH)D3. If your lab uses an older immunoassay that under-detects 25(OH)D2 — many do — your total result can look flat or even fall while you are taking D2 faithfully. If you take D2, ask for an assay (LC-MS/MS) that reports both metabolites.
D2 and D3 have been compared on clinical outcomes Limited evidence
They have not, in any meaningful way. The large trials on fracture, respiratory infection and mortality used D3 or pooled both forms without head-to-head comparison. The case for preferring D3 is entirely a biomarker argument — a solid one, but it is not the same as showing D2 produces worse health outcomes.

Dosage & safety

Studied doseMaintenance 400–2000 IU/day; the prescription deficiency protocol is 50,000 IU weekly for 8–12 weeks then a maintenance dose. Because of the potency difference, some clinicians use roughly 1.5–2x the D3 dose when D2 is used, and daily dosing suits D2 better than large intermittent boluses. The tolerable upper intake level is 4000 IU/day for adults.

SafetyToxicity profile is the same as D3: sustained very high intakes (generally >10,000 IU/day for months) can cause hypercalcaemia, hypercalciuria, nausea, kidney stones and nephrocalcinosis. Particular caution in sarcoidosis and other granulomatous disease, lymphoma, primary hyperparathyroidism, and with thiazide diuretics, where even modest doses can push calcium up. Interacts with digoxin (hypercalcaemia potentiates toxicity). Absorption is impaired by orlistat, cholestyramine and after bariatric surgery. Derived from UV-irradiated fungal ergosterol, so it is vegan and the usual choice where a plant source is required — though vegan D3 from lichen is now widely available. Do not stack multiple products containing vitamin D without adding up the total.

Scientific references

Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis
Tripkovic L, et al. — Am J Clin Nutr, 2012
Daily supplementation with 15 μg vitamin D2 compared with vitamin D3 to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women: a 12-wk randomized, placebo-controlled food-fortification trial
Tripkovic L, et al. — Am J Clin Nutr, 2017

Where to buy

Deva, Vegan Vitamin D2, 60 mcg (2,400 IU), 90 Tablets

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