# Vitamin D deficiency and health impacts > Live situation record from CLSTR: https://clstr.news/situations/20261018-vitamin-d-deficiency-and-health-impacts > Updated: 2026-10-18T03:08:07.000Z. Sources: 5. Developments: 2. Vitamin D is essential for calcium and phosphate metabolism, supporting bone strength, muscle function, and the immune system. While the body synthesizes the vitamin through UVB radiation from sunlight, dietary sources are often insufficient to meet daily requirements. Deficiency can lead to serious health complications, such as muscle weakness, bone pain, osteomalacia in adults, and rickets in children. Risk factors include limited mobility, low sunlight exposure, darker skin pigmentation, and certain chronic conditions affecting the liver, kidneys, or gastrointestinal tract. Certain medications may also impact vitamin levels. In regions like Germany, natural synthesis is typically only possible from March to October, leaving the body to rely on stored reserves during winter. Because both deficiency and excessive supplementation can cause health issues, medical professionals recommend blood tests to measure 25-hydroxyvitamin D levels before beginning a supplementation regimen. ## Timeline ### 2026-10-18: Vitamin D deficiency and supplementation guidelines Vitamin D is essential for bone and immune health, but deficiency risks vary based on sun exposure, skin type, and health conditions. Medical testing is advised before supplementation. 4 sources. https://clstr.news/cluster/vitamin-d-deficiency-and-supplementation-guidelines-1 ### 2026-10-10: Vitamin D deficiency and its impact on health Vitamin D is essential for bone and muscle health. Deficiency can cause serious conditions like osteomalacia or rickets, affecting roughly 30% of adults according to the Robert Koch Institute. 2 sources. https://clstr.news/cluster/vitamin-d-deficiency-and-its-impact-on-health --- Cite as: Vitamin D deficiency and health impacts. CLSTR, https://clstr.news/situations/20261018-vitamin-d-deficiency-and-health-impacts