What is the difference between vitamin D2 and D3?
Both D2 and D3 raise blood vitamin D; D3 may raise levels more and maintain them longer. Manufacturing sources vary, and plant-sourced D3 is available. The product and dose should match the clinical need rather than the form’s name alone.
Details
Names and sources
D2 is ergocalciferol and D3 is cholecalciferol. D2 is commonly manufactured using yeast; D3 may come from lanolin or lichen. If avoiding animal products, check the source and capsule ingredients rather than assuming every D3 product is animal-derived.
Dose matters more than marketing
Prevention differs from treating confirmed deficiency. Malabsorption, kidney disease and certain medicines can affect the plan. Do not switch between a daily product and a high-dose preparation without checking units and dosing frequency.
Is more better?
Vitamin D can accumulate, and excessive supplementation may cause high calcium and complications. Fatigue alone does not establish deficiency, and repeated tests are not necessary for everyone. Discuss whether testing and follow-up are indicated, and count the vitamin D already present in other supplements to avoid unintended duplication.
Related reading: How can vegans obtain vitamin B12, and is a supplement needed?.