Calcium deficiency will jeopardize bone health, such as rickets, osteoporosis, etc., jeopardize neuromuscular, leading to tetany, etc., jeopardize cardiac health and lead to hair thinning, etc. 1. Bone: children lack of vitamin D will have poor bone calcification, growth retardation, new bone formation abnormalities, serious bone deformation and lead to rickets, manifested as square skull, delayed closure of fontanel, chicken chest, funnel chest and so on. Calcium deficiency in adults may lead to osteoporosis, pathologic fracture, osteochondrosis and so on. 2. Neuromuscular: Calcium deficiency will lead to increased neuromuscular excitability, muscle spasm, tetany, convulsions and so on. 3. Myocardium: hypocalcemia will lead to increased excitability and conductivity of myocardium. 4. Other: Calcium deficiency will lead to low immunity and easy to get infected. Chronic long-term calcium deficiency can lead to thinning hair, dry skin and brittle nails. Calcium deficiency may lead to diabetes, cardiovascular disease, hypertension and other chronic diseases, periodontal disease and other related. If symptoms related to calcium deficiency occur, it is recommended to seek medical attention and follow medical advice.