Vitamin D supplements usually contain vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol). Both forms are absorbed and can improve vitamin D status, but they differ in source and in how effectively they may maintain blood levels.
What is vitamin D3?
Vitamin D3 is the form produced in human skin after exposure to sunlight. It is naturally present in foods such as oily fish, egg yolk and some fortified foods. Traditional D3 supplements are often derived from lanolin, while vegan D3 can be produced from lichen or other suitable non-animal sources.
What is vitamin D2?
Vitamin D2 is produced by fungi and is found in some UV-exposed mushrooms and fortified foods. It is commonly used in vegan products, although vegan D3 is now also widely available.
How are D2 and D3 used by the body?
Both forms are converted first in the liver and then in the kidneys into compounds the body can use. They follow similar pathways and both can support vitamin D status when taken regularly.
However, research generally finds that D3 raises and maintains the usual blood marker of vitamin D more effectively than an equivalent amount of D2. This does not make D2 useless; it means product choice, dose and consistency matter.
Which form should you choose?
- For most adults: D3 is a common first choice because of its effectiveness and broad availability.
- For vegans: check whether the D3 is lichen-derived, or choose a clearly labelled vegan D2 product.
- For a diagnosed deficiency: follow the dose and form recommended by a healthcare professional.
- For everyday maintenance: use a product that fits current national guidance and avoid stacking several vitamin D products.
Take vitamin D with or without food?
Vitamin D is fat-soluble, and absorption can be enhanced when it is taken with a meal containing some fat. It does not need to be a high-fat meal; a normal balanced meal is sufficient.
Elexir Vitamin D3 1000 IUFurther reading
Swedish Food Agency: Vitamin D and the difference between D2 and D3
NIH Office of Dietary Supplements: Vitamin D
