Vitamin D deficiency - Wikipedia
https://en.wikipedia.org/wiki/Vitamin_D_deficiencyVitamin D deficiency or hypovitaminosis D is a vitamin D level that is below normal. It most commonly occurs in people when they have inadequate exposure to sunlight, particularly sunlight with adequate ultraviolet B rays (UVB). Vitamin D deficiency can also be caused by inadequate nutritional intake of vitamin D; disorders that limit vitamin D absorption; and disorders that impair the conversion of vitamin D to active metabolites, including certain liver, kidney, and hereditary dis…
Vitamin D Deficiency: MedlinePlus
medlineplus.gov › vitaminddeficiencyMar 24, 2023 · What is vitamin D deficiency? Vitamin D deficiency means that your body is not getting enough vitamin D to stay healthy. Why do I need vitamin D and how do I get it? Vitamin D helps your body absorb calcium. Calcium is one of the main building blocks of bone. Vitamin D also has a role in your nervous, muscle, and immune systems.