Vitamin D plays a key role in skeletal and cardiovascular disorders, cancers, central nervous system diseases, reproductive diseases, infections, and autoimmune and dermatological disorders. The two main sources of vitamin D are sun exposure and oral intake, including vitamin D supplementation and dietary intake. Multiple factors are linked to vitamin D status, such as Fitzpatrick skin type, sex, body mass index, physical activity, alcohol intake, and vitamin D receptor polymorphisms. Patients with photosensitive disorders tend to avoid sun exposure, and this practice, along with photoprotection, can put this category of patients at risk for vitamin D deficiency. Maintaining a vitamin D serum concentration within normal levels is warranted in atopic dermatitis, psoriasis, vitiligo, polymorphous light eruption, mycosis fungoides, alopecia areata, systemic lupus erythematosus, and melanoma patients. The potential determinants of vitamin D status, as well as the benefits and risks of vitamin D (with a special focus on the skin), will be discussed in this article.