Vitamin D Deficiency

About Vitamin D Deficiency

Vitamin D deficiency is very common, with estimates suggesting around a billion people worldwide have low levels. Vitamin D is essential for calcium absorption, bone health, immune function, and muscle function. It is produced in the skin upon UV B exposure, with dietary sources fatty fish, egg yolks, fortified foods being secondary. Risk factors for deficiency include living at high latitudes, dark skin melanin reduces UV B absorption, sunscreen use, indoor lifestyle, obesity vitamin D is sequestered in fat, aging skin produces less, and malabsorption. Symptoms of mild deficiency are often nonspecific fatigue, muscle weakness, bone pain, and mood changes. Severe deficiency in children causes rickets, characterized by soft weak bones, bowed legs, delayed tooth eruption, skeletal deformities, and growth retardation. In adults, severe deficiency causes osteomalacia diffuse bone pain and muscle weakness, and exacerbates osteoporosis. Vitamin D deficiency has been associated with many conditions including autoimmune diseases, cardiovascular disease, certain cancers, depression, and respiratory infections, though causality is debated. Diagnosis is made through serum 25 hydroxyvitamin D levels, with deficiency commonly defined as below 20 ng mL 50 nmol L, although thresholds vary between organizations. Treatment involves vitamin D supplementation, usually cholecalciferol D3, with dose and duration set by a clinician according to the degree of deficiency. Guidance on testing and target levels differs between organizations, and the Endocrine Society 2024 guideline did not endorse routine testing in healthy adults. Excessive supplementation can cause toxicity with hypercalcemia.