Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D₃ and vitamin D₂.

Should you take vitamin D as a supplement?

Taken in appropriate doses, vitamin D is generally considered safe. However, taking too much vitamin D in the form of supplements can be harmful. Children age 9 years and older, adults, and pregnant and breastfeeding women who take more than 4,000 IU a day of vitamin D might experience: Nausea and vomiting.

Are vitamin D supplements all the same?

Vitamin D2 and D3 are both widely used vitamin D supplements but are not the same. Vitamin D2 is ergocalciferol and comes from plant-based sources. Vitamin D3 is cholecalciferol and comes from animal-based sources.