This document provides information on vitamin D, including its history, forms, sources, functions, deficiency, testing, and role in dental health. It discusses the key points that vitamin D is important for calcium absorption and bone mineralization, sources include exposure to sunlight and dietary intake of oily fish, eggs, and fortified foods. Vitamin D deficiency can lead to metabolic bone diseases like rickets in children and osteomalacia in adults, causing bone pain and deformities. Biomarkers and tests are used to diagnose and monitor vitamin D levels.