Upon exposure to ultraviolet UV-B rays in the sun light, 7-DHC is converted into vitamin D3 via previtamin D3 as an intermediate isomer.

[1][2] Lanolin, a waxy substance that is naturally secreted by wool-bearing mammals, contains 7-DHC which is converted into vitamin D by sunlight and then ingested during grooming as a nutrient.

[4] Defective synthesis results in the human inherited disorder lathosterolosis resembling Smith–Lemli–Opitz syndrome.

[4] Mice where this gene has been deleted lose the ability to increase vitamin D3 in the blood following UV exposure of the skin.

[11] Industrially, 7-DHC generally comes from lanolin, and is used to produce vitamin D3 by UV exposure.

[13][14] 7-DHC is used for vitamin D3 synthesis via lanosterol in land animals, via cycloartenol in plants, and in algae together with another provitamin D ergosterol for D2.