25-hydroxyvitamin D is the main manifestation of vitamin D in the body. Low 25-hydroxyvitamin D in women will first manifest as symptoms of hypocalcemia such as cramps and skeletal muscle pain. The clinical definition of 25-hydroxyvitamin D value <75.0nmol/L is vitamin D deficiency, and the value <50.0nmol/L is vitamin D deficiency, so women with values below this range should take vitamin D supplements in a timely manner to avoid inducing the following kinds of diseases and producing adverse effects on the organism: 1. Low 25-hydroxyvitamin D in women will affect the absorption and utilization of calcium and phosphorus in the small intestine, which in turn will affect calcium metabolism in the bones, increasing the incidence of chondromalacia, osteoporosis, pathological fractures and other bone diseases; 2, inducing autoimmune diseases: 25-hydroxyvitamin D is an important component of maintaining cell differentiation, and low values will affect B-lymphocytes, T-lymphocytes and other immune cells in women. Low value of 25-hydroxyvitamin D will affect the normal immune function of B-lymphocytes and T-lymphocytes in women, which will increase the incidence of autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis; 3, affect growth and development: low 25-hydroxyvitamin D in women during the growth and development period will also affect the normal level of hormones, which will affect normal growth and development and promote the development of chicken breast, funnel chest and other body dysplasia 4, resulting in lower blood calcium levels: low levels of 25-hydroxy vitamin D is not conducive to the body's absorption of calcium, which may lower blood calcium levels, which may cause convulsions, cramps, peripheral pain or cardiac arrhythmia; 5, other: the function of various cells, such as cardiac muscle cells, brain cells, pancreatic B cells, skeletal muscle cells, all need the participation of 25-hydroxy vitamin D, so women When the long-term value is low, it also increases the risk of diabetes, hypertension, stroke and other diseases.