The phrase "active form" refers to a state where something or someone is actively engaged or functioning. It means being in a state of action or being in use rather than being passive or inactive. Full definition
Get the same biologically active form of vitamin D produced by the body as a result of sun exposure. (ourpaleolife.com)
A magnesium deficiency can also affect the production of the biologically active form of vitamin D and thereby further promoting osteoporosis. (afibbers.org)
Many of us do not adequately absorb or convert into active forms, the vitamins, minerals, and other nutrients in our food. (jodypowellnd.com)